Refrigerant Report


Refrigerant Report

This edition supersedes all previous issues.

Refrigerant development and legal situation

Stratospheric ozone depletion as well as atmospheric

greenhouse effect due to refrigerant

emissions have led to drastic changes in

the refrigeration and air conditioning technology index

since the beginning of the 1990s.

This is especially true for the area of commercial

refrigeration and air conditioning

systems with their wide range of applications.

In former years the main refrigerants

used for these systems were ozone depleting

types, namely R12, R22 and R502; for

special applications R114, R12B1, R13B1,

R13 and R503 were used.

The use of these substances is no longer

allowed in industrialised countries, but the

use of R22 has been extended through transitional

periods. However, the European

Union also commited to an early phase-out

for R22, which was enforced in several

stages (see page 8). The main reason for

this early ban of R22 contrary to the international

agreement is the ozone depletion

potential although it is only small.

Since 2010, phase-out regulations became

effective in other countries as well, for

instance in the USA.

This implies enormous consequences for

the whole refrigeration and air conditioning

sector. BITZER therefore committed itself to

taking a leading role in the research and

development of environmentally friendly system


After the chlorine-free (ODP = 0) HFC refrigerants

R134a, R404A, R407C, R507A and

R410A have become widely established for

many years in commercial refrigeration, air

conditioning and heat pump systems, new

challenges have come up. They concern primarily

the greenhouse effect: The aim is a

clear reduction of direct emissions caused

by refrigerant losses and indirect emissions

by particularly efficient system technology.

In this area, applicable legal regulations are

already in force, such as the EU F-Gas

Regulation No. 517/2014 (BITZER brochure

A-510) and a series of regulations already

ratified or in preparation as part of the EU

Ecodesign Directive (BITZER brochure

A-530). Similar regulations are also in

preparation or already implemented in Australia,

Canada and the USA. On an international

level, the so-called “Kigali Amendment”

was adopted in 2016 under the

Montreal Protocol, in which a step-by-step

reduction of HFCs (“HFC phase-down”) was

agreed upon starting in 2019.

Even though indirect emissions caused by

energy production are considerably higher

than direct (CO2-equivalent) emissions

caused by HFC refrigerants, refrigerants

with high global warming potential (GWP)

will in the future be subject to use restrictions

or bans. This will affect primarily

R404A and R507A, for which alternatives

with lower GWP are already being offered.

However, in order to achieve the legal

objectives, substitutes for further refrigerants

and increased use of naturally occurring

substances (NH3, CO2, hydrocarbons) will

become necessary.

This requires comprehensive testing of

these refrigerants, suitable oils and adjusted

systems. Therefore a close co-operation

exists with scientific institutions, the refrigeration

and oil industries, component manufacturers

as well as a number of innovative

refrigeration and air conditioning companies.

A large number of development tasks have

been completed. Suitable compressors for

alternative refrigerants are available.

Besides the development projects, BITZER

actively supports legal regulations and self

commitments concerning the responsible

use of refrigerants as well as measures to

increase system and components’ efficiency.

The following report deals with potential

measures of a short to medium-term change

towards technologies with reduced environmental

impact in medium and large size

commercial refrigeration and air conditioning

systems. Furthermore, the experiences so

far and the resulting consequences for plant

technology are discussed.

_ _ _

Several studies confirm that vapour compression

refrigeration systems normally

used commercially are far superior in efficiency

to all other processes down to a cold

space temperature of around -40°C.

The selection of an alternative refrigerant

and the system design receives special significance,

however. Besides the request for

substances without ozone depletion potential

(ODP = 0) especially the energy demand

of a system is seen as an essential

criterion due to its indirect contribution to

the greenhouse effect. On top of that there

is the direct global warming potential (GWP)

due to refrigerant emission.

Therefore a calculation method has been

developed for the qualified evaluation of a

system which enables an analysis of the

total influence on the greenhouse effect.

The so-called “TEWI” factor (Total Equivalent

Warming Impact) has been introduced.

Meanwhile, another, more extensive

assessment method has been developed

considering “Eco-Efficiency”. Hereby, both

ecological (such as TEWI) and economical

criteria are taken into account (further

explanations see page 7).

Therefore it is possible that the assessment

of refrigerants with regard to the environment

can differ according to the place of installation

and drive method.

Upon closer evaluation of substitutes for the

originally used CFC and HCFC as well as

for HFCs with higher GWP, the options with

single-substance refrigerants are very limited.

This includes e.g. R134a, which will be

usable for quite some time based on its

comparatively low GWP. Similarly, the

hydro-fluoro-olefins (HFO) R1234yf and

R1234ze(E) with a GWP < 10, which are

also exempted from the F-Gas regulation.

Direct alternatives (based on fluorinated

hydrocarbons) for almost all refrigerants of

higher volumetric refrigerating capacity and

pressure level than R134a can only be “formulated”

as blends. However, taking into

account thermodynamic properties, flammability,

toxicity and global warming potential,

the list of potential candidates is very limited.

Blends of reduced GWP include in addition

to R134a, R1234yf and R1234ze(E) primarily

the refrigerants R32, R125 and


Besides halogenated refrigerants, Ammonia

(NH3) and hydrocarbons are considered as

substitutes as well. The use for commercial

applications, however, is limited by strict

safety requirements.

Carbon dioxide (CO2) becomes more important

as an alternative refrigerant and secondary

fluid, too. Due to its specific characteristics,

however, there are restrictions to a

general application.

The following illustrations show a structural

survey of the alternative refrigerants and a

summary of the single or blended substances

which are now available. After that the individual

subjects are discussed.

For refrigerant properties, application

ranges and lubricant specifications, see

pages 41 to 44.

For reasons of clarity the less or only

regionally known products are not specified

in this issue, which is not intended to imply

any inferiority.



Fig. 1 Structural classification of refrigerants

* Service refrigerants contain HCFC as blend component. They are therefore subject to the same legal regulations as R22 (see page 8).

As a result of the continued refurbishment of older installations, the importance of these refrigerants is clearly on the decline. For some of them, production has already been

discontinued. However, because of the development history of service blends, these refrigerants will continue to be covered in this Report.

Tab. 1 Substitutes for CFC and HCFC refrigerants (chlorine free HFCs)



Global Warming and

TEWI Factor

As already mentioned (see chapter Refrigerant

developments and legal situation,

page 3), a method of calculation has been

developed to judge the influence upon the

global warming effect for the operation of

individual refrigeration plants (TEWI = Total

Equivalent Warming Impact).

All halocarbon refrigerants (including the

non-chlorinated HFCs) belong to the category

of greenhouse gases. An emission of

these substances contributes to the global

warming effect. The influence is however

much greater in comparison to CO2, which

is the main greenhouse gas in the atmosphere

(in addition to water vapour). Based

on a time horizon of 100 years, the emission

from 1 kg R134a is for example roughly

equivalent to 1430 kg of CO2 (GWP =


Thus, the reduction of refrigerant losses

must be one of the main tasks for the


On the other hand, the major contributor to

a refrigeration plant’s global warming effect

is the (indirect) CO2 emission caused by

energy generation. Based on the high percentage

of fossil fuels used in power stations,

the average European CO2 release is

around 0.45 kg per kWh of electrical energy.

This results in a significant greenhouse

effect over the lifetime of the plant.

time horizon 100 years

Due to a deciding proportion of the total balance,

there is not only a need for alternative

refrigerants with a favorable (thermodynamic)

energy balance, but an increase in demand

for highly efficient compressors

and associated equipment as well as optimised

system components and system control.

When various compressor designs are compared,

the difference of indirect CO2 emission

(due to the energy requirement) can

have a larger influence upon the total effect

than the refrigerant losses.

A usual formula is shown in Fig. 2. The

TEWI factor can be calculated and the various

areas of influence are correspondingly


An additional example is shown in Fig. 3

(medium temperature with R134a) shows

Fig. 2 Method for the calculation of TEWI figures

TEWI values with various refrigerant

charges, leakage losses and energy consumptions.

This example is simplified based on an

overall leak rate as a percentage of the

refrigerant charge. The actual values vary

very strongly, so that the potential risk of

individually constructed systems and extensively

branched plants is especially high.

Great effort is taken worldwide to reduce

greenhouse gas emissions, and legal regulations

have partly been developed already.

Since 2007, the “Regulation on certain fluorinated

greenhouse gases” – which also

defines stringent requirements for refrigeration

and air conditioning systems – has

become valid for the EU. Meanwhile, the

revised Regulation No. 517/2014 entered

into force and has to be applied since January


Environmental aspects



An assessment based on the specific TEWI

value takes into account the effects of global

warming during the operating period of a

refrigeration, air conditioning or heat pump

installation. However, not the entire ecological

and economical aspects are considered.

But apart from ecological aspects, economical

aspects are highly significant when evaluating

technologies and making investment

decisions. With technical systems, the

reduction of environmental impact frequently

involves high costs, whereas low costs

often have increased ecological consequences.

For most companies, the investment

costs are decisive, whereas they are

often neglected during discussions about

minimizing ecological problems.

For the purpose of a more objective assessment,

studies* were presented in 2005 and

2010, using the example of supermarket

refrigeration plants to describe a concept for

evaluating Eco-Efficiency. It is based on

the relationship between added value (a

product’s economic value) and the resulting

environmental impact.

With this evaluation approach, the entire life

cycle of a system is taken into account in

terms of:

o ecological performance in accordance

with the concept of Life Cycle Assessment

as per ISO 14040,

o economic performance by means of a

Life Cycle Cost Analysis.

This means that the overall environmental

impact (including direct and indirect emissions),

as well as the investment costs,

operating and disposal costs, and capital

costs are taken into account.

The studies also confirm that an increase of

Eco-Efficiency can be achieved by investing

in optimized plant equipment (minimized

operating costs). Hereby, the choice of

refrigerant and the associated system technology

play an important role.

Eco-Efficiency can be illustrated in graphic

representation (Example, see Fig. 5). The

results of the Eco-Efficiency evaluation are

shown on the x-axis in the system of coordinates,

whilst the results of the life cycle cost

analysis are shown on the y-axis. This

shows clearly: A system that is situated

higher in the top right quadrant exhibits an

increasingly better Eco-Efficiency – and

conversely, it becomes less efficient in the

bottom left sector.

The diagonals plotted into the system of

coordinates represent lines of equal Eco-

Efficiency. This means that systems or processes

with different life cycle costs and

environmental impacts can quite possibly

result in the same Eco-Efficiency.


Environmental aspects


Fig. 6 R12/R22 – comparison of discharge gas temperatures of

a semi-hermetic compressor

Fig. 7 R12/R22/R502 – comparison of pressure levels

refrigerant in new systems and for service

purposes due to its ozone depletion potential

– although being low.

With regard to components and system

technology a number of particularities are to

follow as well. Refrigerant R22 has approximately

55% higher refrigerating capacity and

pressure levels than R12**. The significantly

higher discharge gas temperature is also a

critical factor compared to R12 (Fig. 6) and


Similar relationships in terms of thermal load

are found in the comparison with HFC refrigerants

R134a, R404A/R507A (pages 9 and 17).

Resulting design criteria

Particularly critical – due to the high discharge

gas temperature – are low temperature

plants especially concerning thermal

stability of oil and refrigerant, with the danger

of acid formation and copper plating.

Special measures have to be adopted

therefore, such as two stage compression,

controlled refrigerant injection, additional

cooling, monitoring of discharge gas temperature,

limiting the suction gas superheat

and particularly careful installation.

* Not allowed for new equipment in Germany and

Denmark since January 1st, 2000 and in Sweden

as of 1998.

Since January 1st, 2001 restrictions apply to the

other member states of the EU as well. The measures

concerned are defined in the ODS Regulation

1005/2009 of the EU commision on ozone depleting

substances amended in 2009. This regulation also

governs the use of R22 for service reasons within

the entire EU.

Since 2010, phase-out regulations in other countries,

such as the USA, are valid.

R22 as transitional refrigerant

Although chlorine-free refrigerants, such as

R134a and R404A/R507A (Fig. 1 and Tab.

1) have been widely used − but are already

being replaced by alternatives with lower

GWP in the EU for example − R22 is still

used internationally in many areas, both for

new installations and for retrofitting existing


Reasons are relatively low investment costs,

especially compared with R134a systems,

but also its large application range, favourable

thermodynamic properties and low

energy requirement. Additionally, R22 and

components are available world wide, which

is not guaranteed everywhere for the chlorine

free alternatives.

Despite of the generally favourable properties

R22 is already subject to various regional

restrictions* which control the use of this

HCFC refrigerants

There are also limitations in the application

with low evaporating temperatures to be


Comprehensive tests have demonstrated

that the performance of R134a exceeds theoretical

predictions over a wide range of

compressor operating conditions. Temperature

levels (discharge gas, oil) are even

lower than with R12 and, therefore, substantially

lower than R22 values. There are

thus many potential applications in air conditioning

and medium temperature refrigeration

plants as well as in heat pumps. Good

heat transfer characteristics in evaporators

and condensers (unlike zeotropic blends)

favour an economical use.

R134a is also characterized by a comparably

low GWP (1430). Therefore, in view of

future restrictions (for example EU F-Gas

Regulation), the use of this refrigerant will

still be possible for quite some time. If

required, systems can later be converted

relatively easily to non-flammable (A1)

HFO/HFC alternatives with a GWP of

approx. 600 (pages 24/25).

Lubricants for R134a and other HFCs

The traditional mineral and synthetic oils are

not miscible (soluble) with R134a and other

HFCs described in the following and are

therefore only insufficiently transported

around the refrigeration circuit.

Immiscible oil can settle out in the heat

exchangers and prevent heat transfer to

such an extent that the plant can no longer

be operated.

New lubricants were developed with the

appropriate solubility and have been in use

for many years. These lubricants are based

on Polyol Ester (POE) and Polyalkylene

Glycol (PAG).

For further explanations on lubricants see

chapter “Lubricants for compressors”, page


R134a as substitute for

R12 and R22

R134a was the first chlorine free (ODP = 0)

HFC refrigerant that was tested comprehensively.

It is now used world-wide in many

refrigeration and air conditioning units with

good results. As well as being used as a

pure substance, R134a is also applied as a

component of a variety of blends (see also

“Refrigerant blends”, page 13).

R134a has similar thermodynamic

properties to R12:

Refrigerating capacity, energy demand,

temperature properties and pressure levels

are comparable, at least in air conditioning

and medium temperature refrigeration

plants. This refrigerant can therefore be

used as an alternative for most former R12


For some applications R134a is even preferred

as a substitute for R22, an important

reason being the limitations to the use

of R22 in new plants and for service. However,

the lower volumetric refrigerating

capacity of R134a (Fig. 9) requires a larger

compressor displacement than with R22.

HFC refrigerants


Supplementary BITZER information

concerning the use of R134a

(see also

o Technical Information KT-620

“HFC Refrigerant R134a”

o Technical Information KT-510

„Polyolester oils for reciprocating


o Special edition

„A new generation of compact screw

compressors optimised for R134a“

Resulting design and construction


Suitable compressors are required for

R134a with a special oil charge and adapted

system components. The normal metallic

materials used in CFC plants have also

been proven with ester oils; elastomers

must sometimes be matched to the changing

situation. This is especially valid for flexible

hoses where the requirements call for a

minimum residual moisture content and low


The plants must be dehydrated with particular

care and the charging or changing of

lubricant must also be done carefully. In

addition relatively large driers should be

provided, which have also to be matched to

the smaller molecule size of R134a.

Meanwhile, many years of very positive

experience with R134a and ester oils

have been accumulated. For this refrigerant,

BITZER offers an unequalled

wide range of reciprocating, screw and

scroll compressors.

Converting existing R12 plants to


At the beginning this subject was discussed

very controversially, several conversion

methods were recommended and applied.

Today there is a general agreement on

technically and economically matching solutions.

The characteristics of ester oils are very

favourable here: Under certain conditions

they can be used with CFC refrigerants,

they can be mixed with mineral oils and tolerate

a proportion of chlorine up to a few

hundred ppm in an R134a system.

The remaining moisture content has, however,

an enormous influence. Very thorough

evacuation (removal of remaining chlorine

and dehydration) is therfore essential, as

well as the installation of generously dimensioned

driers. There is doubtful experience

with systems where the chemical stability

was already insufficient with R12 operation

e.g. with bad maintenance, small drier

capacity, high thermal loading. Increased

deposition of oil decomposition products

containing chlorine is found often. These

products are released by the influence of

the highly polarized mixture of ester oil and

R134a and find their way into the compressor

and control devices. Conversion should

therefore be limited to systems which are in

a good condition.

Restrictions for R134a in mobile

air conditioning (MAC) systems

An EU Directive on “Emissions from MAC

systems” bans the use of R134a in new

systems. Various alternative technologies

are already in use. For further explanation

see pages 11, 12, and 36.

HFC refrigerants


Alternatives to R134a

For mobile air conditioning systems (MAC)

with open drive compressors and hose connections

in the refrigerant circuit, the risk of

leakages is considerably higher than with

stationary systems. An EU Directive

(2006/40/EC) has been passed to reduce

direct emissions in this application area.

Within the scope of the Directive, and starting

2011, type approvals for new vehicles

will only be granted if they use refrigerants

with a global warming potential (GWP) of

less than 150. Consequently, this excludes

R134a (GWP = 1430) which has been used

so far in these systems.

Meanwhile, alternative refrigerants and new

technologies were developed and tested.

This also involved a closer examination of

the use of R152a.

For quite some time the automotive industry

has agreed on so-called “Low GWP” refrigerants.

The latter is dealt with as follows.

CO2 technology, favored for this application

for quite some time, has not been widely

implemented for a variety of reasons (see

also pages 12 and 36).

R152a – an alternative

to R134a (?)

R152a is very similar to R134a with regard

to volumetric refrigerating capacity (approx.

-5%), pressure levels (approx. -10%) and

energy efficiency. Mass flow, vapour density

and thus also the pressure drop are even

more favourable (approx. -40%).

R152a has been used for many years as a

component in blends, but not as a single

substance refrigerant till now. Especially

advantageous is the very low global warming

potential (GWP = 124).

R152a is flammable – due to its low fluorine

content – and classified in safety group A2.

As a result, increased safety requirements

demand individual design solutions and

safety measures along with the corresponding

risk analysis.

For this reason, the use of R152a in mobile

air conditioning systems for passenger cars

(MAC) has not been implemented yet.

“Low GWP” HFO refrigerant


The ban on the use of R134a in mobile air

conditioning systems within the EU has triggered

a series of research projects. In addition

to CO2 technology (see chapter CO2 in

mobile air conditioning systems, page 36),

refrigerants with very low GWP values and

similar thermodynamic properties as R134a

have been developed.

In early 2006, two refrigerant mixtures were

introduced under the names “Blend H”

(Honeywell) and “DP-1” (DuPont). INEOS

Fluor followed with another version under

the trade name AC-1. In the broadest

sense, all of these refrigerants were blends

of various fluorinated molecules.

During the development and test phase it

became obvious that not all acceptance

criteria could be met, and thus further

examinations with these blends were discontinued.

Consequently, DuPont (meanwhile

Chemours) and Honeywell bundled their

research and development activities in a

joint venture which focused on 2,3,3,3-

tetrafluoropropene (CF3CF=CH2). This

refrigerant, designated R1234yf, belongs to

the group of hydro fluoro olefins (HFO).

These refrigerants are unsaturated HFCs

with a chemical double bond.

HFC refrigerants


With view to the relatively simple conversion

of mobile air conditioning systems, this

technology prevailed up to now over the

competing CO2 systems.

However, as already explained before, due

to the flammability of R1234yf, investigations

focus on other technical solutions.

This includes active fire-extinguishing devices

(e.g. with argon), but also enhancements

of CO2 systems.

For detailed information on properties and

the application, see chapter “Low GWP”

HFOs and HFO/HFC blends as alternatives

to HFCs, page 24.

Toxicity investigations have shown very

positive results, as well as compatibility

tests of the plastic and elastomer materials

used in the refrigeration circuit. Some lubricants

show increased chemical reactivity

which, however, can be suppressed by a

suitable formulation and/or addition of


Operating experiences gained from laboratory

and field trials to date allow a positive

assessment, particularly with regard to performance

and efficiency behaviour. For the

usual range of mobile air conditioning operation,

refrigerating capacity and coefficient

of performance (COP) are within a range of

5% compared with that of R134a. Therefore,

it is expected that simple system modifications

will provide the same performance

and efficiency as with R134a.

The critical temperature and pressure levels

are also similar, while the vapour densities

and mass flows are approximately 20%

higher. The discharge gas temperature with

this application is up to 10 K lower.

The global warming potential is extremely

low (GWP = 4). When released to the atmosphere,

the molecule rapidly disintegrates

within a few days, resulting in a very low

GWP. This raises certain concerns regarding

the long-term stability in refrigeration circuits

under real conditions.

However, extensive testing has demonstrated

the required stability for mobile air conditioning


R1234yf has lower flammability as measured

by ASTM 681, but requires significantly

more ignition energy than R152a, for

instance. Due to its low burning velocity and

the high ignition force, it received a classification

of the new safety group “A2L” according

to ISO 817.

In extensive test series, it has been shown

that a potentially increased risk of the refrigerant

flammability in MAC systems can be

avoided by implementing suitable constructive

measures. However, some investigations

(e.g. by Daimler) also show an increased

risk. This is why various manufacturers

have intensified again the development

of alternative technologies.

HFC refrigerants


Refrigerant blends

Refrigerant blends have been developed for

existing as well as for new plants with properties

making them comparable alternatives

to the previously used substances.

It is necessary to distinguish between three


  1. Transitional or service blends

which mostly contain HCFC R22 as the

main constituent. They are primarily

intended as service refrigerants for

older plants with view on the use ban of

R12, R502 and other CFCs. Corresponding

products are offered by various manufacturers,

there is practical experience

covering the necessary steps of conversion


However, the same legal requirements as

for R22 apply to the use and phase-out of

these blends (see page 8).

  1. HFC blends

These are substitutes for the refrigerants

R502, R22, R13B1 and R503. Above all,

R404A, R507A, R407C and R410A, are

being used to a great extent.

One group of these HFC blends also contains

hydrocarbon additives. The latter

exhibit an improved solubility with lubricants,

and under certain conditions they

allow the use of conventional oils. In many

cases, this permits the conversion of existing

(H)CFC plants to chlorine-free refrigerants

(ODP = 0) without the need for an oil


  1. HFO/HFC blends

as successor generation of HFC refrigerants.

It concerns blends of new “Low

GWP” refrigerants (e.g. R1234yf) with

HFCs. The fundamental target is an additional

decrease of the global warming potential

(GWP) as compared to established

halogenated substances (see page 24).

Blends of two and three components already

have a long history in the refrigeration trade.

A difference is made between the so called

“azeotropes” (e.g. R502, R507A) with thermodynamic

properties similar to single substance

refrigerants, and “zeotropes” with

“gliding” phase changes (also see next

chapter). The original development of

“zeotropes” mainly concentrated on special

applications in low temperature and heat

pump systems. Actual system construction,

however, remained the exception.

A somewhat more common earlier practice

was the mixing of R12 to R22 in order to

improve the oil return and to reduce the discharge

gas temperature with higher pressure

ratios. It was also usual to add R22 to

R12 systems for improved performance, or

to add hydrocarbons in the extra low temperature

range for a better oil transport.

This possibility of specific “formulation” of

certain characteristics was indeed the basis

for the development of a new generation of


At the beginning of this Report (see chapter

Refrigerant developments and legal situation,

page 3) it was already explained that

no direct single-substance alternatives (on

the basis of fluorinated hydrocarbons) exist

for the previously used and current refrigerants

of higher volumetric refrigeration capacity

than R134a. This is why they can only

be “formulated” as blends. However, taking

into account thermodynamic properties,

flammability, toxicity and global warming

potential, the list of potential candidates is

strongly limited.

For the previously developed CFC and

HCFC substitutes, the range of substances

was still comparably large, due to the fact

that substances of high GWP could also be

used. However, for formulating blends with

significantly reduced GWP, in addition to

R134a, R1234yf and R1234ze(E), primarily

refrigerants R32, R125 and R152a can be

used. Most of them are flammable. They

also exhibit considerable differences with

respect to their boiling points, which is why

all “Low GWP” blends of high volumetric

refrigerating capacity have a substantial

temperature glide (see next chapter).

BITZER has accumulated extensive

experience with refrigerant blends.

Laboratory and field testing was commenced

at an early stage so that basic

information was obtained for the optimizing

of the mixing proportions and

for testing suitable lubricants. Based

on this data, a large supermarket plant

– with 4 BITZER semi-hermetics in parallel

– could already be commissioned

in 1991. The use of these blends in the

most varied systems has been state-ofthe-

art for many years – generally with

good experiences.

General characteristics of zeotropic


As opposed to azeotropic blends (e.g.

R502, R507A), which behave as single substance

refrigerants with regard to evaporation

and condensing processes, the phase

change with zeotropic fluids occurs in a

“gliding” form over a certain range of temperature.

This “temperature glide” can be more or

less pronounced, it depends mainly on the

boiling points and the percentage proportions

of the individual components. Certain

supplementary definitions are also used,

depending on the effective values, such as

“near-azeotrope” or “semiazeotrope” for

less than 1 K glide.

Essentially, this results in a small temperature

increase already in the evaporation

phase and a reduction during condensing.

In other words: At a certain pressure level,

the resulting saturation temperatures differ

in the liquid and vapour phases (Fig. 11).

To enable a comparison with single substance

refrigerants, the evaporating and

condensing temperatures have been often

defined as mean values. As a consequence

the measured subcooling and

superheating conditions (based on mean

values) are unrealistic. The effective difference

– based on dew and bubble temperature

– is less in each case. These factors

are very important when assessing the minimum

superheat at the compressor inlet

(usually 5 to 7 K) and the quality of the

refrigerant after the liquid receiver.

Refrigerant blends

With regard to a uniform and easily comprehensible

definition of the rated compressor

capacity, the revised standards EN 12900

and AHRI540 are applied. Evaporating and

condensing temperatures refer to saturated

conditions (dew points).

o Evaporating temperature according to

point A (Fig. 11)

o Condensing temperature according to

point B (Fig. 11)

In this case the assessment of the effective

superheat and subcooling temperatures will

be simplified.

It must however be considered that the

actual refrigerating capacity of the system

can be higher than the rated compressor

capacity. This is partly due to an effectively

lower temperature at the evaporator inlet.

A further characteristic of zeotropic refrigerants

is the potential concentration shift

when leakage occurs. Refrigerant loss in

the pure gas and liquid phases is mainly

non-critical. Leaks in the phase change

areas, e.g. after the expansion valve, within

the evaporator and condenser/receiver are

considered more significant. It is therefore

recommended that soldered or welded

joints should be used in these sections.

Extended investigations have shown in the

meantime that leakage leads to less serious

changes in concentration than initially

thought. In any case it is certain that the following

substances of safety group A1 (see

page 41) which are dealt with here cannot

develop any flammable mixtures, either

inside or outside the circuit. Essentially similar

operating conditions and temperatures

as before can be obtained by supplementary

charging with the original refrigerant in

the case of a small temperature glide.

Further conditions/recommendations concerning

the practical handling of blends

must also be considered:

o The plant always has to be charged with

liquid refrigerant. When vapour is taken

from the charging cylinder, concentration

shifts may occur.

o Since all blends contain at least one

flammable component, the entry of air

into the system must be avoided. If the

proportion of air is too high, a critical shift

of the ignition point can occur under high

pressure and while evacuating.

o The use of blends with a significant temperature

glide is not recommended for

plants with flooded evaporators. A large

concentration shift is to be expected in

this type of evaporator, and as a result

also in the circulating refrigerant mass


Refrigerant blends


Service blends with the basic

component R22* as substitutes

for R502

As a result of the continued refurbishment

of older installations, the importance of

these refrigerants is clearly on the decline.

For some of them, production has already

been discontinued. However, because of

the development history of service blends,

these refrigerants will continue to be covered

in this Report.

These refrigerants belong to the group of

“Service blends” and have been offered

under the designations R402A/R402B*

(HP80/HP81 – DuPont), R403A/R403B*

(formerly ISCEON® 69S/69L) and R408A*

(“Forane®” FX10 – Arkema).

The basic component is in each case R22,

the high discharge gas temperature of

which is significantly reduced by the addition

of chlorine free substances with low

isentropic compression exponent (e.g.

R125, R143a, R218). A characteristic feature

of these additives is an extraordinarily

high mass flow, which enables the mixture

to achieve a great similarity to R502.

R290 (Propane) is added as the third component

to R402A/B and R403A/B to improve

miscibility with traditional lubricants

as hydrocarbons have especially good solubility


For these blends two variations are offered

in each case. When optimizing the blend

variations with regard to identical refrigerating

capacity as for R502 the laboratory

measurements showed a significantly increased

discharge gas temperature (Fig. 13),

which above all, with higher suction gas

superheat (e.g. supermarket use) leads to

limitations in the application range.

On the other hand a higher proportion of

R125 or R218, which has the effect of reducing

the discharge gas temperature to the

level of R502, results in somewhat higher

refrigerating capacity (Fig. 14).

With regard to material compatibility the

blends can be judged similarly to (H)CFC

refrigerants. The use of conventional refrigeration

oil (preferably semi or full synthetic)

is also possible due to the R22 and

R290 proportions.

Apart from the positive aspects there are

also some disadvantages. These substances

are alternatives only for a limited time.

The R22 proportion has (although low) an

ozone depletion potential. Furthermore, the

additional components R125, R143a and

R218 have a high global warming potential


Resulting design criteria/

Converting existing R502 plants

The compressor and the components which

are matched to R502 can remain in the system

in most cases. The limitations in the

application range must however be considered:

Higher discharge gas temperature

than R502 with R402B**, R403A** and

R408A** or higher pressure levels with

R402A** and R403B**.

The good solubility characteristics of R22

and R290 increase the risk that, after conversion

of the plant, possible deposits of oil

decomposition products containing chlorine

are dissolved and find their way into the

compressor and control devices. Systems

where chemical stability was already insufficient

with R502 operation (bad maintenance,

low drier capacity, high thermal

loading) are particularly at risk.

Thus, generously dimensioned suction gas

filters and liquid line driers should be installed

for cleaning before conversion, and

an oil change should be made after approximately

100 hours operation. Further checks

are recommended.

* When using blends containing R22 legal regulations

are to be observed, see page 8.

** Classification according to ASHRAE nomenclature.

Fig. 13 Effect of the mixture variation upon the discharge

gas temperature (example: R22/R218/R290)

Fig. 14 Comparison of the performance data of a semi-hermetic



Service blends


The operating conditions with R502 (including

discharge gas temperature and suction

gas superheat) should be noted so that a

comparison can be made with the values

after conversion. Depending upon the

results, control devices should possibly be

reset and other additional measures should

be taken as required.

Service blends as

substitutes for R12 (R500)

Although (as experience already shows)

R134a is also well suited for the conversion

of existing R12 plants, the general use for

such a “retrofit” procedure is not always

possible. Not all compressors which have

previously been installed are designed for

the application with R134a. In addition a

conversion to R134a requires the possibility

to make an oil change, which is for example

not the case with most hermetic type compressors.

Economical considerations also arise, especially

with older plants where the effort of

converting to R134a is relatively high. The

chemical stability of such plants is also

often insufficient and thus the chance of

success is very questionable.

Therefore “Service blends” are also available

for such plants as an alternative to R134a

and are offered under the designations

R401A/R401B, R409A. The main components

are the HCFC refrigerants R22, R124

and/or R142b. Either HFC R152a or R600a

(Isobutane) is used as the third component.

Operation with traditional lubricants (preferably

semi or full synthetic) is also possible

due to the major proportion of HCFC.

A further service blend was offered under

the designation R413A (ISCEON® 49 –

DuPont), but replaced by R437A by the end

of 2008. However, because of the development

history of service blends, R413A will

continue to be covered in this Report. The

constituents of R413A consist of the chlorine

free substances R134a, R218, and

R600a. In spite of the high R134a content,

the use of conventional lubricants is possible

because of the relatively low polarity

of R218 and the favourable solubility of


R437A is a blend of R125, R134a, R600

and R601 with similar performance and

properties as R413A. This refrigerant also

has zero ODP.

However, due to the limited miscibility of

R413A and R437A with mineral and alkylbenzene

oils, oil migration may result in

systems with a high oil circulation rate

and/or a large liquid volume in the receiver

– for example if no oil separator is installed.

If insufficient oil return to the compressor is

observed, the refrigerant manufacturer

recommends replacing part of the original

oil charge with ester oil. But from the compressor

manufacturer’s view, such a measure

requires a very careful examination of

the lubrication conditions. For example, if

increased foam formation in the compressor

crankcase is observed, a complete change

to ester oil will be necessary. Moreover,

under the influence of the highly polarized

blend of ester oil and HFC, the admixture of

or conversion to ester oil leads to increased

dissolving of decomposition products and

dirt in the pipework. Therefore, generously

dimensioned suction clean-up filters must

be provided. For further details, see the

refrigerant manufacturer’s “Guidelines”.

Resulting design criteria/

Converting existing R12 plants

Compressors and components can mostly

remain in the system. However, when using

R413A and R437A the suitability must be

checked against HFC refrigerants. The

actual “retrofit” measures are mainly restricted

to changing the refrigerant (possibly

oil) and a careful check of the superheat

setting of the expansion valve.

A significant temperature glide is present

due to the relatively large differences in the

boiling points of the individual substances,

which requires an exact knowledge of the

saturation conditions (can be found from

vapour tables of refrigerant manufacturer

and in the BITZER Refrigerant App) in order

to assess the effective suction gas superheat.

In addition the application range must also

be observed. Different refrigerant types are

required for high and low evaporating temperatures

or distinct capacity differences

must be considered. This is due to the

steeper capacity characteristic, compared to


Due to the partially high proportion of R22

especially with the low temperature blends,

the discharge gas temperature with some

refrigerants is significantly higher than with

R12. The application limits of the compressor

should therefore be checked before


The remaining application criteria are similar

to those for the substitute substances for

R502 which have already been mentioned.

* By using R22 containing blends the legal requirements

are to be followed, see chapter R22 as transitional

refrigerant, page 8.

Service blends


R404A and R507A as

substitutes for R22 and R502

These blends are chlorine free substitutes

(ODP = 0) for R22 as well as for R502 in

medium and low temperature ranges.

A composition which was already launched

at the beginning of 1992 is known under the

trade name Suva® HP62 (DuPont). Long

term use has shown good results. Further

blends were traded as Forane® FX70

(Arkema) and Genetron® AZ50 (Allied Signal/

Honeywell) or Solkane® 507 (Solvay).

HP62 and FX70 have been listed in the

ASHRAE nomenclature as R404A and

AZ50 as R507A.

The basic components belong to the HFC

group, where R143a belongs to the flammable

category. Due to the combination

with a relatively high proportion of R125

the flammability is effectively counteracted,

even in the case of leakage.

A feature of all three ingredients is the very

low isenropic compression exponent which

results in a similar, with even a tendency to

be lower, discharge gas temperature to

R502 (Fig. 15). The efficient application of

single stage compressors with low evaporating

temperatures is therefore guaranteed.

Due to the similar boiling points for R143a

and R125, with a relatively low proportion of

Fig. 15 R404A/R502 – comparison of discharge gas temperatures of a

semi-hermetic compressor

Fig. 16 Comparison of performance data of a semi-hermetic


R134a, the temperature glide with the ternary

blend R404A within the relevant application

range is less than one Kelvin. The

characteristics within the heat exchangers

are therefore not very different than with

azeotropes. The results obtained from heat

transfer measurements show favourable


R507A is a binary substance combination

which even gives an azeotropic characteristic

over a relatively wide range. The conditions

therefore tend to be even better.

The performance (Fig. 16) gives hardly any

difference between the various substances

and ist very similar to R502. This also

explains the high market penetration of

these refrigerants. With regard to the thermodynamic

properties, they are particularly

suitable for commercial medium and low

temperature systems.

Typical metallic materials are compatible

with HFC refrigerants. Elastomers, however,

must be adapted to the changed characteristics.

Suitable lubricants are polyol esters

(see chapter Lubricants for compressors,

page 40).

The relatively high global warming potential

(GWP = 3922 .. 3985), which is mainly

determined by the R143a and R125, is

something of a hitch. However, it is better

than R502 and with regard to the favourable

energy demand also leads to a reduction of

the TEWI value. Other improvements are

possible in this respect due to further developed

system control.

Nevertheless, due to their high global warming

potential (GWP), the use of R404A and

R507A will no longer be allowed in the EU

in new installations from 2020. This has

been settled in the F-Gas Regulation No.

517/2014 to be applied since 2015. However,

the current requirement of phase-down

in connection with a strict quota system will

lead to an earlier phase-out in many applications.

For more detailed information,

please refer to BITZER brochure A-510.

In the USA, Canada and Australia there are

also requirements to phase-out R404A and

R507A. For an international phase-down

(starting in 2019) of HCFC and HFC refrigerants,

the so-called Kigali Amendment was

agreed upon in 2016 as part of the Montreal


Alternatives with lower GWP are the HFC

blends explained in the following (from page

18), as well as HFO/HFC blends being developed

and evaluated (from page 24).

Halogen free refrigerants or cascade

systems using different refrigerants are

also an option for specific applications

(from page 28).

Substitutes for R22 in refrigeration systems


R407A/407B/407F/407H as

substitutes for R22 and R502

As an alternative to the earlier described

substitutes, additional mixtures have been

developed based on R32 which is chlorine

free (ODP = 0) and flammable like R143a.

The refrigerant R32 is also of the HFC type

and initially was regarded as a main candidate

for R22 alternatives (page 20). However,

due to extent of blend variations comparable

thermodynamic characteristics to

R404A/R507A can also be obtained.

These kind of refrigerants were marketed at

first under the trade name KLEA® 60/61

(ICI) and are listed as R407A/R407B* in the

ASHRAE nomenclature.

Honeywell has developed another blend

with the trade name Performax® LT (R407F

according to ASHRAE nomenclature) and

introduced it into the market, similar Daikin

Chemical with R407H. For both blends, the

R32 proportion is higher than for R407A,

while the R125 proportion is lower. With

R407H, this results in certain restrictions for

low temperature applications.

However, the necessary conditions for alternatives

containing R32 are not quite as

favourable compared to the R143a based

substitutes discussed earlier. The boiling

point of R32 is very low at -52°C, in addition

the isentropic compression exponent is

even higher than with R22. Rather high proportions

of R125 and R134a are necessary

to match the characteristics at the level of

R404A and R507A. The flammability of R32

is thus effectively suppressed, but the large

differences in boiling points with a high proportion

of R134a lead to a larger temperature


The main advantage of R32 is the extraordinarily

low global warming potential (GWP =

675), so that even in combination with R125

and R134a it is significantly lower than with

the R143a based alternatives mentioned

above (R407A: GWP = 2107, R407F: GWP

= 1825, R407H: GWP = 1490).

Thus, they also comply with the requirement

of the new EU F-Gas Regulation

which from 2020 will only allow refrigerants

of GWP < 2500.

Measurements made with R32 containing

blends do show certain capacity reductions

compared to R404A and R507A, with low

evaporating temperatures. The COP however

shows less deviation and is even higher

in medium temperature applications (Fig. 18).

* Meanwhile, R407B is no longer available in the market.

Due to the historical development of HFC blends

this refrigerant will, however, still be considered in

this Report.

Resulting design criteria

The system technology can be based on

the experience with R22 and R502 over a

wide area.

On the thermodynamic side, a heat exchanger

between the suction and liquid

line is recommended as this will improve

the refrigerating capacity and COP.

BITZER offers the whole program of

reciprocating, scroll and screw compressors

for R404A and R507A.

Supplementary BITZER information concerning

the use of HFC blends

(see also

o Technical Information KT-651

„Retrofitting of R22 systems to

alternative refrigerants”

o Technical Information KT-510

„Polyolester oils for reciprocating


Fig. 17 R407A, R407F/R404A – comparison of discharge gas temperature of a

semi-hermetic compressor

Fig. 18 Comparison of performance data of a semi-hermetic



Sub s ti tut e s fo r R22 in r e fr ige rat io n s yst e ms


Whether these favourable conditions are

confirmed in real applications is subject to

the system design. An important factor is

the significant temperature glide, which can

have a negative influence upon the capacity/

temperature difference of the evaporator

and condenser.

With regard to the material compatibility,

R32 blends can be assessed similarly to

R404A and R507A; the same applies to the


Despite the relatively high proportion of

R125 and R134a in the R32 blends, the discharge

gas temperature is higher than with

the R143a based alternatives (especially for

R407F and even to a higher degree with

R407H). This results in certain limitations in

the application range as well as the requirement

for additional cooling of compressors

when operating at high pressure ratios.

2-stage compressors can be applied very

efficiently where especially large lift conditions

are found. An important advantage in

this case is the use of a liquid subcooler.

Resulting design criteria

The experience with R404A/R507A and

R22 can be used for plant technology in

many respects, although the temperature

glide as well as the difference in the thermodynamic

properties have to be considered.

This especially concerns the design

and construction of heat exchangers and

expansion valves.

Converting existing R22 plants to


Practical experiences show that qualified

conversions are possible. Compared to R22

the volumetric refrigeration capacity is nearly

similar while the refrigerant mass flow is

only slightly higher. These are relatively

favourable conditions for the conversion of

medium and low temperature R22 systems.

The main components can remain in the

system provided that they are compatible

with HFC refrigerants and ester oils.

However, special requirements placed on

the heat exchanger with regard to the significant

temperature glide must be considered.

A conversion to ester oil is also necessary,

which leads to increased dissolving of decomposition

products and dirt in the

R422A as substitute

for R22 and R502

Amongst other aims, R422A (ISCEON®

MO79 – Chemours) was developed in order

to obtain a chlorine-free refrigerant (ODP = 0)

for the simple conversion of existing medium

and low temperature refrigeration

systems using R22 and R502.

For this, it was necessary to formulate a

refrigerant with comparable performance

and energy efficiency to that of R404A,

R507A, and R22, which also permits the

use of conventional lubricants.

R422A is a zeotropic blend of the basic

components R125 and R134a with a small

addition of R600a. Due to its relatively high

R134a percentage, the temperature glide

(see chapter Refrigerant Properties, page

42) lies higher than for R404A, but lower

than other refrigerants with the same component

blends – such as R417A and R422D

(see page 22).

The adiabatic exponent, and therefore also

the discharge gas and oil temperatures of the

compressor, are lower than for R404A and

R507A. At extremely low temperatures, this

can be advantageous. However, in cases of

low pressure ratio and suction gas superheat,

this can be a disadvantage due to increased

refrigerant solution if ester oil is used.

The material compatibility is comparable to

the blends mentioned previously, the same

applies to the lubricants. On account of the

good solubility of R600a, conventional lubricants

can also be used under favourable


In particular, advantages result during the

conversion of existing R22 and R502

systems as mentioned above. However, for

plants with high oil circulation rates and/or

large liquid charge in the receiver, oil migration

might occur – for example if no oil

separator is installed.

If insufficient oil return to the compressor is

observed, the refrigerant manufacturer

recommends replacing part of the original

oil charge with ester oil. But from the compressor

manufacturer’s view, such a measure

requires a very careful examination of

the lubrication conditions. For example, if increased

foam formation in the compressor

crankcase is observed, a complete change

to ester oil* will be necessary. Under the

influence of the highly polarized blend of

ester oil and HFC, the admixture of or conversion

to ester oil leads to increased dissolving

of decomposition products and dirt

in the pipework. Therefore, generously

dimensioned suction clean-up filters must

be provided. For further details, see the

refrigerant manufacturer’s “Guidelines”.

From a thermodynamic point of view, a heat

exchanger between suction and liquid line

is recommended, improving the refrigerating

capacity and coefficient of performance. Besides

this the resulting increase in operating

temperatures leads to more favourable

lubricating conditions (lower solubility).

Due to the high global warming potential

(GWP ≥ 2500), R422A will no longer be

allowed for new installations in the EU from

2020 onwards. The requirements and restrictions

are specified in the F-Gas Regulation


* General proposal for screw compressors and liquid

chillers when used with DX evaporators with internally

structured heat exchanger tubes. Furthermore, an

individual check regarding possible additional measures

will be necessary.

BITZER compressors are suitable for

R422A. An individual selection is possible

upon demand.

pipework. Therefore, generously dimensioned

suction clean-up filters must be provided.

Conversion of existing R404A/R507A

systems to R407A/407B/407F/407H

Larger differences in thermodynamic properties

(e.g. mass flow, discharge gas temperature)

and the temperature glide of

R407A/F/H may require the replacement of

control components and if necessary

retrofitting of additional compressor cooling

when existing systems are converted.

For newly built systems, a specific design

of components and system is necessary.

BITZER offers a comprehensive program

of reciprocating and screw compressors

for R407A und R407F. An individual

selection of compressors for R407H is

possible upon demand.

Substitutes for R22 in refrigeration systems

Fig. 19 R407C/R22 – comparison of performance data of a semi-hermetic


Fig. 20 R407C/R22 – comparison of pressure levels

Thus, R407C also complies with the requirement

of the new EU F-Gas Regulation

which from 2020 onwards will only

allow refrigerants with GWP < 2500. However,

the quantity limitation through the

“phase-down” will also lead to significantly

restricted availability.

The high temperature glide is a disadvantage

for usual applications which requires

appropriate system design and can have a

negative influence on the efficiency of the

heat exchangers (see chapter General characteristics

of zeotropic blends, page 13).

Due to the properties mentioned, R407C is

preferably an R22 substitute for air conditioning

and heat pump systems and (within

certain limitations) also for medium temperature

refrigeration. In low temperature

refrigeration, because of the high proportion

of R134a, a significant drop in refrigerating

capacity and COP is to be expected. There

is also the danger of an increased R134a

concentration in the blend in evaporators,

with reduced performance and malfunctioning

of the expansion valve (e.g. insufficient

suction gas superheat).

Material compatibility is similar to that of the

blends discussed previously; the same applies

to lubricants.

* Previous trade names are not used any more.

R407C as substitute

for R22

Mixtures of HFC refrigerants R32, R125 and

R134a were considered to be the preferred

candidates for short-term substitutes for

R22 in the EU in view of the early ban of

R22. Performance values and efficiency are

highly comparable (Fig. 19). At first two

blends of the same composition have been

introduced under the trade names AC9000*

(DuPont) and KLEA® 66* (ICI). They are

listed in the ASHRAE nomenclature as

R407C. In the meantime there are also further

blend varieties (e.g. R407A/R407F/

R407H) with somewhat differing compositions,

whose properties have been optimized

for particular applications (see page 18).

Unlike the substitutes for R22 in refrigeration

systems with identical blend components

(pages 18 and 19), the substitutes for

R22 in air conditioning systems and heat

pumps under consideration contain higher

proportions of R32 and R134a. A good correspondence

with the properties of R22 in

terms of pressure levels, mass flow, vapour

density and volumetric refrigerating capacity

is thus achieved. In addition, the global

warming potential is relatively low (GWP =

1774), which is a good presupposition for

favourable TEWI values.

Substitutes for R22 in air conditioning

systems and heat pumps

As the HCFC refrigerant R22 (ODP = 0.05)

is accepted only as a transitional solution, a

number of chlorine-free (ODP = 0) alternatives

have been developed and tested extensively.

They are being used for a large

range of applications.

Experience shows, however, that none of

these substitutes can replace the refrigerant

R22 in all respects. Amongst others there

are differences in the volumetric refrigerating

capacity, restrictions in possible applications,

special requirements in system

design and considerably differing pressure

levels. According to the specific operating

conditions, various alternatives may be considered.

Apart from the single-component HFC refrigerant

R134a, these are mainly blends

(different compositions) of the components

R32, R125, R134a, R143a, and R600(a).

The following description mainly concerns

the development and potential applications

of these. The halogen-free substitutes NH3,

propane and propylene as well as CO2

should also be considered, however, specific

criteria must be applied for their use

(description from page 28).

In addition, R32 and HFO/HFC blends can

also be used as alternatives (see chapter

R32 as substitute for R22, from page 23).


Substitutes for R22 in A/C and heat pumps


Fig. 21 R410A/R22 – comparison of performance data of a semi-hermetic


Fig. 22 R410A/R22 – comparison of pressure

Resulting design criteria

With regard to system technology, previous

experience with R22 can only be utilized to

a limited extent.

The distinctive temperature glide requires a

particular design of the main system components,

e.g. evaporator, condenser, expansion

valve. In this context it must be

considered that heat exchangers should

preferably be laid out for counterflow operation

and with optimized refrigerant distribution.

There are also special requirements

with regard to the adjustment of control

devices and service handling.

Furthermore, the use in systems with flooded

evaporators is not recommended as this

would result in a severe concentration shift

and layer formation in the evaporator.

BITZER can supply a widespread range

of semi-hermetic reciprocating, screw

and scroll compressors for R407C.

Converting existing R22 plants to R407C

Because of the above mentioned criteria,

no general guidelines can be defined. Each

case must be examined individually.

R410A as substitute for R22

In addition to R407C, the near-azeotropic

mixture listed by ASHRAE as R410A is

available and widely used for medium-sized

capacities in air conditioning and heat pump


An essential feature indicates nearly 50%

higher volumetric refrigerating capacity (Fig.

21) compared to R22, but with the consequence

of a proportional rise in system

pressures (Fig. 22).

At high condensing temperatures, energy

consumption/COP initially seems to be less

favourable than with R22.

This is mainly due to the thermodynamic

properties. On the other hand, very high

isentropic efficiencies are achievable (with

reciprocating and scroll compressors), so

that the real differences are lower.

Another aspect are the high heat transfer

coefficients in evaporators and condensers

determined in numerous test series, resulting

in especially favourable operating conditions.

With an optimized design, it is quite

possible for the system to achieve a better

overall efficiency than with other refrigerants.

Because of the negligible temperature glide

(< 0.2 K), the general usability is similar to

that of a pure refrigerant.

The material compatibility is comparable to

the previously discussed blends, the same

applies to the lubricants. However, the pressure

levels and the higher specific loads on

the system components need to be taken

into account.

Resulting design criteria

The fundamental criteria for HFC blends

also apply to the system technology with

R410A. However, the high pressure levels

have to be considered (43°C condensing

temperature already corresponds to 26 bar


Compressors and other system components

designed for R22 are not suitable for this

refrigerant (or only to a limited extent).

Though, suitable compressors and system

components are available.

When considering to cover usual R22 application

ranges, the significant differences in

the thermodynamic properties (e.g. pressure

levels, mass and volume flow, vapour

density) must be taken into account. This

also requires considerable constructional

Substitutes for R22 in A/C and heat pumps


R427A as a substitute for R22

This refrigerant blend was introduced some

years ago under the trade name Forane®

FX100 (Arkema) and is now listed in the

ASHRAE nomenclature as R427A.

The R22 substitute is offered for the conversion

of existing R22 systems for which a

“zero ODP” solution is requested. It is an

HFC mixture with base components


In spite of the blend composition based on

pure HFC refrigerants, the manufacturer

states that a simplified conversion procedure

is possible.

This is facilitated by the R143a proportion.

Accordingly, when converting from R22 to

R427A, all it takes is a replacement of the

original oil charge with ester oil. Additional

flushing sequences are not required, as

proportions of up to 15% of mineral oil

and/or alkyl benzene have no significant

effect on oil circulation in the system.

However, it must be taken into account that

the highly polarized mixture of ester oil and

HFC will lead to increased dissolving of

decomposition products and dirt in the pipework.

Therefore, generously dimensioned

suction clean-up filters must be provided.

Regarding refrigerating capacity, pressure

levels, mass flow and vapor density, R427A

is relatively close to R22. During retrofit,

essential components such as expansion

valves can remain in the system. Due to the

high proportion of blend components with

low adiabatic exponent, the discharge gas

temperature is considerably lower than with

R22, which has a positive effect at high

compression ratios.

It must be taken into account that this is

also a zeotropic blend with a distinct temperature

glide. Therefore the criteria described

for R407C apply here as well.

hydrocarbon additive. It is offered under

trade name ISCEON® MO29 (Chemours)

and listed as R422D in the ASHRAE


Another refrigerant belonging to the category

of HFC/HC blends was introduced in

2009 under the trade name ISCEON®

MO99 (Chemours) – ASHRAE classification

R438A. This formulation was designed

especially for a higher critical temperature

for applications in hot climate

areas. The base components are R32,

R125, R134a, R600 and R601a.

Like R407C, all four substitute refrigerants

are zeotropic blends with a more or less

significant temperature glide. In this respect,

the criteria described for R407C

also apply here.

Apart from a similar refrigeration capacity,

there are fundamental differences in thermodynamic

properties and in oil transport

behaviour. The high proportion of R125

causes a higher mass flow with R417A/B

and R422D than with R407C, a lower discharge

gas temperature and a relatively

high superheating enthalpy. These properties

indicate that there are differences in the

optimization of system components, and a

heat exchanger between liquid and suction

lines is of advantage.

Despite the predominant proportion of HFC

refrigerants, conventional lubricants can be

used to some extent because of the good

solubility of the hydrocarbon constituent.

However, in systems with a high oil circulation

rate and/or a large volume of liquid in

the receiver, oil migration may result.

In such cases, additional measures are

necessary. For further information on oil

return and lubricants see chapter “R422A

as substitute for R22 and R502” (page 19).

Due to the high global warming potential

(GWP ≥ 2500), R417B and R422D will no

longer be allowed for new installations in

the EU from 2020. The requirements and

restrictions are specified in the F-Gas Regulation

517/2014. However, the “phasedown”

quantity limitation will also lead to

significantly restricted availability of R417A

and R438A.

BITZER compressors are suitable for use

with R417A/417B/422D/438A. An individual

selection is possible upon request.

changes to compressors, heat exchangers,

and controls, as well as measures of tuning

vibrations. There are stricter safety requirements,

e.g. affecting the quality and dimensions

of piping and flexible tube elements

(for condensing temperatures of approx.

60°C/40 bar).

Another criterion is the relatively low critical

temperature of 73°C. Irrespective of the

design of components on the high pressure

side, the condensing temperature is thus


R410A complies with the requirements of

the EU F-Gas Regulation, which will only

allow refrigerants with GWP < 2500 from

2020 onwards. However, the quantity limitation

through the “phase-down” will also

lead to significantly restricted availability.

Due to the extremely high demand for

R410A, a timely switch to alternatives is

needed in the EU.

For R410A, BITZER offers a series of

semi-hermetic reciprocating compressors

and scroll compressors.


as substitutes for R22

Similar to the development of R422A (page

19), one aim of developing these blends

was to provide chlorine-free refrigerants

(ODP = 0) for the simple conversion of

existing R22 plants.

R417A was introduced to the market years

ago, and is also offered under the trade

name ISCEON® MO59 (Chemours). This

substitute for R22 contains the blend components

R125/R134a/R600 and therefore

differs considerably from e.g. R407C with a

correspondingly high proportion of R32.

Meanwhile, a further refrigerant based on

identical components, but with a higher

R125 content, has been offered under the

ASHRAE designation R417B. Due to its

lower R134a content, its volumetric refrigerating

capacity and pressure levels are higher

than for R417A. This results in different

performance parameters and a different

focus within the application range.

The same applies to a further blend with the

same main components, but R600a as

Substitutes for R22 in A/C and heat pumps


R32 as substitute for R22

As described earlier, R32 belongs to the

HFC refrigerants, but initially it was mainly

used as a component of refrigerant blends

only. An essential barrier for the application

as a pure substance so far is the flammability.

This requires adequate charge limitations

and/or additional safety measures,

especially with installations inside buildings.

In addition there are very high pressure

levels and discharge gas temperatures

(compression exponent higher than with

R22 and R410A).

On the other hand, R32 has favorable thermodynamic

properties, e.g. very high evaporating

enthalpy and volumetric refrigerating

capacity, low vapor density (low

pressure drop in pipelines), low mass flow,

and favorable power input for compression.

The global warming potential is relatively

low (GWP = 675).

Looking at these favorable properties and

taking into account the additional effort for

emission reductions, R32 will increasingly

be used as a refrigerant in factory produced

systems (A/C units and heat pumps) with

low refrigerant charges.

It was proven in flammability tests that the

necessary ignition energy is very high and

Fig. 23 R32/R410A – comparison of performance and operating data

of a scroll compressor

the flame speed is low. Therefore, R32

(like R1234yf and R1234ze) has been

placed in the new safety group A2L according

to ISO 817.

The resulting safety requirements are specified

in the revised EN 378 (amended version


R32 is also considered an alternative for

systems with larger refrigerant charge, e.g.

liquid chillers for air conditioning and process

applications and heat pumps previously

operated with R410A. However,

depending on the installation site of the

system, appropriate refrigerant charge

limits must be observed. On the other

hand, there are no such restrictions when

installed outdoors (without access to unauthorized

persons) and in machine rooms

(for example, according to EN 378-3:

2016). It should be noted, however, that

R32 precharged chillers may be subject to

special conditions during transport (according

to the Pressure Equipment Directive,

R32 is classified under Fluid Group 1).

BITZER scroll compressors of the ORBIT

GSD6 and GSD8 series have been

approved and released for use with R32.

Depending on the product group, a

special compressor version may be


R427A meets the requirement of the EU

F-Gas Regulation, which will only allow

refrigerants with GWP < 2500 from 2020.

However, the quantity limitation due to the

“phase-down” will also lead to significantly

restricted availability.

BITZER compressors are suitable for

R427A. An individual selection is possible

upon demand.

Supplementary information concerning

the use of HFC blends

(see also

o Technical information KT-651

“Retrofitting R22 systems to alternative


Substitutes for R22 in A/C and heat pumps


HFOs and HFO/HFC blends

Aspects on the development of

HFO and HFO/HFC refrigerants

The decision to use the “low GWP” refrigerant

R1234yf in mobile air conditioning systems

for passenger cars (see pages 11/12)

also led to the development of alternatives

for further mobile applications as well as

stationary refrigeration, air conditioning and

heat pump systems.

Primary objectives are the use of singlecomponent

refrigerants and of mixtures

with significantly reduced GWP and similar

thermodynamic properties as the HFCs

currently used predominantly.

An essential basic component for this is

R1234yf (CF3CF=CH2). This refrigerant

belongs to the group of hydro-fluoro-olefins

(HFO), i.e. unsaturated HFCs with molecular

double bonds. This group of HFOs also

includes another substance called

R1234ze(E), which has been mainly used

as a propellant for PU foam and aerosol.

R1234ze(E) differs from R1234yf in its

molecular structure.

Both substances are the preferred choice

in terms of their properties and are also

used as basic components in HFO/HFC

blends. The Global Warming Potential is

very low − R1234yf with GWP 4 and

R1234ze(E) with GWP 7. However, these

refrigerants are flammable (safety class

A2L), meaning the refrigerant quantity in

the system must be considered in light of

the installation location. In addition, there

remain open questions concerning the

long-term stability in stationary systems

where long life cycles are common. Furthermore

the volumetric refrigerating

capacity is relatively low; for R1234yf it is

close to the level of R134a, and more than

20% lower for R1234ze(E).

There is also some uncertainty concerning

flammability. In safety data sheets,

R1234ze(E) is declared as non-flammable.

However, this only applies to its transport

and storage. When used as a refrigerant, a

higher reference temperature for flammability

tests of 60°C applies. At this temperature,

R1234ze(E) is flammable and therefore

classified in safety class A2L, like


R1234ze(E) is sometimes referred to as a

R134a substitute, but its volumetric refrigerating

capacity is more than 20% lower

than that of R134a or R1234yf. The boiling

point (-19°C) also greatly restricts the application

at lower evaporation temperatures.

Its preferred use is therefore in liquid

chillers and high temperature applications.

For further information see chapter Refrigerants

for special applications, page 37.

The list of further potential HFO refrigerants

is relatively long. However, there are

only few substances that meet the requirements

in terms of thermodynamic properties,

flammability, toxicity, chemical stability,

compatibility with materials and lubricants.

These include e.g. the non-flammable

(safety group A1) low-pressure refrigerants

R1336mzz(Z), R1233zd(E) and R1224yd(Z).

These are primarily an option for liquid

chillers with large turbo-compressors, and

they can be used with positive displacement

compressors in high-temperature

applications. R1233zd(E) and R1224yd(Z)

belong to the group of HCFO (hydrochloro-

fluoro-olefins); they have a (very)

low ozone depletion potential (ODP). Upon

release into the atmosphere, however, the

molecule rapidly disintegrates.

On the other hand, there are currently no

candidates from the HFO family with similar

volumetric refrigerating capacity such as

R22/R407C, R404A/R507A and R410A

available for commercial use. Direct alternatives

for these refrigerants with significantly

lower GWPs must therefore be “constructed”

as a mixture of R1234yf and/or

R1234ze(E) with HFC refrigerants, possibly

also small proportions of hydrocarbons,

CO2 or other suitable molecules.

Though, due to the properties of the HFC

refrigerants suitable as blend components,

flammability and GWP are related diametrically

to one another. In other words: Blends

as alternatives to R22/R407C of GWP

< approx. 900 are flammable. This is also

true with alternatives for R404A/R507A in

blends of GWP < approx. 1300 and for

R410A in blends of GWP < approx. 2000.

The reason for this is the high GWP of

each of the required non-flammable components.

There are a few exceptions, which

are discussed in chapter Further development

projects with “Low GWP” refrigerants,

page 26.

For R134a alternatives, the situation is

more favorable. Due to the already quite

low GWP of R134a, a blend with R1234yf

and/or R1234ze(E) allows a formulation of

non-flammable refrigerants with a GWP of

approx. 600.

Thus, primarily two directions for development

are pursued:

o Non-flammable HFC alternatives

(blends) with GWP values according to

the above mentioned limits – safety

group A1. Regarding safety requirements,

these refrigerants can then be

utilized similar to currently used HFCs.

o Flammable HFC alternatives (blends)

with GWP values below the above mentioned

possible limits – according to

safety group A2L (for refrigerants of

lower flammability).

This group of refrigerants is then subject to

charge limitations according to future requirements

for A2L refrigerants.

Meanwhile, there are development projects

using refrigerant components with a much

higher volumetric refrigerating capacity and

pressure than R1234yf and R1234ze(E).

These can then be used to “formulate” mixtures

with R32 as an alternative to R410A,

which are optimised for certain properties.

See additional information in chapter Further

development projects with “Low GWP”

refrigerants, page 26.

R134a alternatives

In addition to the flammable HFO refrigerants

R1234yf and R1234ze(E) already

described, non-flammable mixtures are

now also available as R134a alternatives.

As previously mentioned, the initial situation

is most favorable for these.

They achieve GWP values of approx. 600 −

less than half of R134a (GWP = 1430). In

addition, this type of blends can have

azeotropic properties, so that they can be

used like pure refrigerants.


HFOs and HFO/HFC blends

For quite some time a blend has been

applied on a larger scale in real systems –

this was developed by Chemours and is

called OpteonTM XP-10. Results available

today are promising.

This is also true for an R134a alternative

designated Solstice® N-13 and offered by

Honeywell which, however, differs regarding

the blend composition.

The refrigerants are listed in the ASHRAE

nomenclature under R513A (Chemours)

and R450A (Honeywell).

The same category also includes the refrigerant

blends ARM-42 (ARKEMA) as well

as R456A (Mexichem AC5X).

All options show refrigerating capacity,

power input, and pressure levels similar to

R134a. Thus, components and system

technology can be taken over, only minor

changes like superheat adjustment of the

expansion valves are necessary.

Polyolester oils are suitable lubricants

which must meet special requirements, e.g.

for the utilization of additives.

Prospects are especially favorable for

supermarket applications in the medium

temperature range in a cascade with CO2

for low temperature, just as in liquid chillers

with higher refrigerant charges where the

use of flammable or toxic refrigerants

would require comprehensive safety measures.

A special case is the refrigerant R515B: an

azeotropic mixture of R1234ze(E) and

small amounts of R227ea. This combination,

declared by the manufacturer Honeywell

as an R134a alternative, is nonflammable

(A1) despite the very low GWP

of approx. 300.

However, as with the previously described

R1234ze(E), this can only be considered

an alternative under certain restrictions.

The volumetric refrigerating capacity is also

more than 20% lower than that of R134a or


Substitutes for R404A/R507A and


Since the available HFO molecules

(R1234yf und R1234ze) show a considerably

smaller volumetric refrigerating capacity

than the above mentioned HFC refrigerants,

relatively large HFC proportions with

high volumetric refrigerating capacity must

be added for the particular alternatives.

The potential list of candidates is rather

limited, one option is R32 with its relatively

low GWP of 675.

However, one disadvantage is its flammability

(A2L), resulting also in a flammable

blend upon adding fairly large proportions

in order to increase the volumetric refrigerating

capacity while maintaining a favorable


For a non-flammable blend, on the other

hand, a fairly large proportion of refrigerants

with high fluor content (e.g. R125)

must be added. A drawback here is the

high GWP of more than approx. 900 for

non-flammable R22/R407C alternatives

and more than approx. 1300 with options

for R404A/ R507A. Compared to R404A/

R507A, however, this means a reduction

down to a third.

The future drastic “phase-down” of F-Gases,

e.g. as part of the EU F-Gas Regulation,

already leads to a demand for R404A/

R507A substitutes with GWP values clearly

below 500. Although this is possible with

an adequate composition of the blend (high

proportions of HFO, R152a, possibly also

hydrocarbons), the disadvantage will be its

flammability (safety groups A2L or A2). In

this case, the application will have higher

safety requirements and will need an adequately

adjusted system technology.

R410A currently has no non-flammable

alternatives for commercial applications.

Either R32 (see page 23) as pure substance

or blends of R32 and HFO can be

used. Due to its high volumetric refrigerating

capacity, this requires a very high proportion

of R32, which is why only GWP values

from approx. 400 to 500 can be achieved.

With a higher HFO proportion, the GWP

can be reduced even further, but at the

cost of a clearly reduced refrigerating capacity.

All blend options described above with

R1234yf and R1234ze(E) show a more or

less distinct temperature glide due to boiling

point differences of the individual components.

The same criteria apply as described

in context with R407C.

Beyond that, the discharge gas temperature

of most R404A/R507A alternatives is

considerably higher than for these HFC


In single stage low temperature systems

this may lead to restrictions in the compressor

application range or require special

measures for additional cooling. In transport

applications or in low temperature

systems with smaller condensing units, the

compressors used can often not meet the

required operating ranges, due to the high

discharge gas temperatures. This is why

refrigerant blends based on R32 and HFO

with a higher proportion of R125 have also

been developed. The GWP is slightly

above 2000, but below the limit of 2500 set

in the EU F-Gas Regulation from 2020. The

main advantage of such blends is their

moderate discharge gas temperature,

which allows the operation within the typical

application limits of R404A.

Tab 4 shows the potential blend components

for the alternatives described above.

With some refrigerants the mixture components

for R22/R407C and R404A/R507A

substitutes are identical, but their distribution

in percent is different.

In the meantime, Chemours, Honeywell,

Arkema, Mexichem and Daikin Chemical

have offered corresponding chemical variants

for laboratory and field tests, and in

some cases already for commercial use. A

number of refrigerants are still declared as

being under development and are only

made available for testing purposes under


special agreements. Until now, trade

names are often used although a larger

number of HFO/HFC blends are already

listed in the ASHRAE nomenclature.

Tab. 5 lists a range of currently available

refrigerants or refrigerants declared as

development products. Due to the large

number of different versions and the potential

changes in development products,

BITZER has so far tested only some of the

new refrigerants. This is why in the tables

on pages 41/42 (Tab. 6/7) for the time

being only refrigerant properties of nonflammable

alternatives for R134a and

R404A/R507A (GWP < 1500) are listed

which have already received an ASHRAE

number and are commercially available.

For testing the “Low GWP” refrigerants,

AHRI (USA) has initiated the “Alternative

Refrigerants Evaluation Program (AREP)”.

It was established to investigate and evaluate

a series of the products including halogen-

free refrigerants. Some of these are

also listed in Tab 5.

Further development projects with “Low

GWP” refrigerants

For specific applications, Chemours has

developed a non-flammable (A1) R410A

alternative, which is marketed in selected

countries and regions under the trade

name OpteonTM XP41 – listed by ASHRAE

as R463A.

It is a mixture of R32, R125, R1234yf,

R134a and CO2 with a GWP of 1494.

Despite the high proportion of R32 and

R1234yf, flammability is suppressed by

mixing with R125, R134a and CO2.

Regarding thermodynamics, the differences

to R410A are comparatively small. The

addition of CO2, however, leads to a

distinct temperature glide, which may

cause certain limitations for the application

and places particular demand on the

design of the heat exchangers.

All mixture components and their properties

are well known, which means there are no

additional particularities regarding material

compatibility in comparison to the already

known R410A alternatives.

The supply of compressors for laboratory

or field tests requires an individual review

of the specific application and a special


In the meantime, Honeywell has unveiled

the new development of a non-flammable

(A1) R410A alternative under the trade

name Solstice® N-41 – listed by ASHRAE

as R466A.

R466A is a mixture of R32, R125 and

R13I1 (CF3I − trifluoroiodomethane), an

iodine-methane derivative not previously

used in refrigeration. CF3I is not flammable,

as is R125, which means that the

refrigerant is not flammable (A1), even with

the relatively high proportion of R32 (A2L).

Despite the noticeable proportion of R125

with a GWP of 3500 (AR4), the total GWP

is 733 (AR4) and therefore in the range of

R32, R447B and R452B, which are classified

as A2L.

From a thermodynamic point of view, the

differences between R410A and R466A are

relatively small. Volumetric refrigerating

capacity, pressure levels and discharge

temperature are slightly higher, the refrigerant

mass flow deviates slightly more

(about 15 to 20% higher). The temperature

glide is also very low.

Hence, R466A appears to be a promising

substitute for R410A. However, due to the

CF3I share, there are still uncertainties

regarding long-term chemical stability and

material compatibility under the special

requirements of the refrigeration cycle.

Further investigation is required, so a final

assessment of R466A is currently not possible.

In any case, as matters stand, this

refrigerant cannot be used in state-of-theart

systems (retrofit). The supply of compressors

for laboratory tests requires an

individual review of the specific application

as well as a special agreement.

AGC Chemicals propagates R1123

(CF2=CHF) mixed with R32, partially with

addition of R134yf, as an alternative to

R410A and pure R32. It is an HCFO with

very low ozone depletion potential (ODP).

R1123 has a significantly higher volumetric

refrigeration capacity than R1234yf or

R1234ze(E) and is advantageous in this

respect. However, the pressure level is

even higher than of R32 and the critical

temperature is only about 59°C. Apart from

that, there are unanswered questions about

the chemical long-term stability under the

special requirements of the refrigeration

cycle. According to the safety data sheet,

this substance is also subject to very stringent

safety requirements.

A final assessment of these mixtures is

therefore currently not possible.

Comment from a compressor manufacturer’s

point of view:

It should be an aim to limit the product

variety currently becoming apparent and to

reduce the future supply to a few “standard

refrigerants”. It will not be possible for

component and equipment manufacturers

nor for installers and service companies to

deal in practice with a larger range of


BITZER was involved early on in various

projects with HFO/HFC blends and was

thus able to gain important insight into

the use of these refrigerants. Semi-hermetic

reciprocating compressors of the

ECOLINE series as well as CS. and HS.

screw compressors can already be used

with this new generation of refrigerants.

Several of them have already been

qualified and approved, the respective

performance data is available on the


Scroll compressors of the ORBIT GSD6

and GSD8 series are approved and released

for the use of the R32/HFO mixtures

R452B and R454B. Depending on the

product group, a special compressor

version may be required.

Further information on the application

of HFOs and HFO/HFC blends see brochure

A-510, section 6 and brochure

No. 378 20 387.

HFOs and HFO/HFC blends


HFOs and HFO/HFC blends


Low GWP” Alternatives for HFC refrigerant


ASHRAE Trade Composition GWP③ Safety Boiling tempe- Temperature

Number Name (with blends) AR4 (AR5) group rature [°C]④ glide [K]⑤

R450A Solstice® N-13 Honeywell R1234ze(E)/134a 604 (547) A1 -24 0.6

R456A AC5X⑥ Mexichem R32/1234ze(E)/134a 687 (627) A1 -30 4.8


OpteonTM XP10 Chemours

R1234yf/134a 631 (573) A1 -30 0

R513A⑧ Daikin Chemical

R515B② – Honeywell R1234ze(E)/227ea 293 (299) A1 -19 0

R1234yf various _ 4 (< 1) A2L -30 0

R1234ze(E)② various _ 7 (< 1) A2L -19 0

R444A AC5⑥ Mexichem R32/152a/1234ze(E) 92 (89) A2L -34 10

R516A ARM-42⑦ Arkema R1234yf/R152a/R134a 142 (131) A2L -29 0

R448A Solstice® N-40 Honeywell R32/125/1234yf/1234ze(E)/134a 1387 (1273) A1 -46 6.2


OpteonTM XP40 Chemours

R32/125/1234yf/134a 1397 (1282) A1 -46 5.7

Forane® 449 Arkema

R460B LTR4X⑥ Mexichem R32/125/1234ze(E)/134a 1352 (1242) A1 -45 8.2

R452A OpteonTM XP44 Chemours R32/125/1234yf 2140 (1945) A1 -47 3.8

R452C R452C⑦ Arkema R32/125/1234yf 2220 (2019) A1 -48 3.4

R460A LTR10⑥ Mexichem R32/125/1234ze(E)/134a 2103 (1911) A1 -45 7.4


OpteonTM XL40 Chemours

R32/1234yf 239 (238) A2L -48 5.7

R454A⑧ Daikin Chemical

– ARM-20b⑦ Arkema R32/1234yf/152a 251 (251) A2L -47 6.1

R454C② OpteonTM XL20 Chemours R32/1234yf 148 (146) A2L -46 7.8

R455A Solstice® L-40X Honeywell R32/1234yf/CO2 148 (146) A2L -52 12.8

R457A② ARM-20a⑦ Arkema R32/1234yf/152a 139 (139) A2L -43 7.2

R459B② LTR1⑥ Mexichem R32/1234yf/1234ze(E) 144 (143) A2L -44 7.9

R465A ARM-25⑦⑨ Arkema R32/1234yf/290 145 (143) A2 -52 11.8

R449C OpteonTM XP20 Chemours R32/125/1234yf/134a 1251 (1146) A1 -44 6.1

R32 various – 675 (677) A2L -52 0


OpteonTM XL55 Chemours

R32/125/1234yf 698 (676) A2L -51 0.9

Solstice® L-41y Honeywell

R454B OpteonTM XL41 Chemours R32/1234yf 466 (467) A2L -51 1.0

R459A ARM-71a⑦ Arkema R32/1234yf/1234ze(E) 460 (461) A2L -50 1.7

R463A OpteonTM XP41⑩ Chemours R32/125/1234yf/134a/CO2 1494 (1377) A1 -59 12.2

R466A Solstice® N-41⑧⑩ Honeywell R32/125/13I1(CF3I) 733 (696) A1 -52 0.7

Current Alternatives Components / Mixture components “Low GWP” alternatives


Safety GWP④ R1234yf R1234ze(E) R32 R152a R134a R125 R13I1⑤ CO2

② R290②

Group A2L A2L A2L A2 A1 A1 A1 A1 A3

GWP 4 7 675 124 1430 3500 <1 1 3

A1 ~ 600 _ _ _ _


A2L < 150 _ _ _ _ _

GWP 1430

A2L < 10 _ _

A1 < 2500① _ _ _

A1 ~ 1400 _ _ _ _ _


A2L < 250 _ _ _

GWP 3922/3985

A2L③ < 150 _ _ _

A2 < 150 _ _ _

A1 900..1400 _ _ _ _ _

R22/R407C A2L < 250 _ _ _

GWP 1810/1774 A2L < 150 _ _

A2 < 150 _ _ _

A1 < 1500 _ _ _ _ _

R410A A1 < 750 _ _ _

GWP 2088 A2L < 750 _

A2L ~ 400..750 _ _ _ _

Tab. 5

Low GWP” alternatives for HFC refrigerants

① The relatively low GWP allows the use of R134a also on longer term.

② Lower volumetric refrigerating capacity than reference refrigerant

③ AR4: according to IPCC IV // AR5: according to IPCC V – time horizon 100 years

④ Rounded values

⑤ Total glide from bubble to dew line at 1 bar (abs.)

⑥ Development product

⑦ Available 2018 .. 2020

⑧ Marketing presumably in 2019

⑨ Preferably for commercial appliances

⑩ See information under chapter Further development

projects with „Low GWP“ refrigerants.



Tab. 4 Potential mixture components for “Low GWP” alternatives (examples)



① Refrigerating capacity, mass flow, discharge gas temperature similar to R404A

② Only low percentage – due to temperature glide (CO2) and flammability (R290)

③ R32/HFO blends show lower refrigerating capacity than reference refrigerant, the addtion of CO2 leads to high temperature glide

④ Approx. values according to IPCC IV (AR4)

⑤ R13I1 (CF3I − tri-fluoroiodomethane) is an iodine-methane derivative


GWP 1430①


GWP 1810/1774


GWP 2088


GWP 3922/3985



NH3 (Ammonia) as

alternative refrigerant

The refrigerant NH3 has been used for more

than a century in industrial and larger refrigeration

plants. It has no ozone depletion potential

and no direct global warming potential.

The efficiency is at least as good as that

of R22, in some areas even more favourable;

the contribution to the indirect global

warming effect is therefore small. In addition,

its price is exceptionally low. Is it therefore

an ideal refrigerant and an optimum substitute

for R22 or an alternative for HFCs!?

NH3 has indeed very positive features,

which can be exploited quite well in large

refrigeration plants.

Unfortunately there are also negative aspects,

which restrict the wider use in the commercial

area or require costly and sometimes

new technical developments.

A disadvantage with NH3 is the high isentropic

exponent (NH3 = 1.31 / R22 = 1.19 /

R134a = 1.1), which results in a discharge

temperature even significantly higher than

that of R22. Single stage compression is

therefore already subject to certain restrictions

below an evaporating temperature of

around -10°C.

The question of suitable lubricants is also

not satisfactorily solved for smaller plants in

some kinds of applications. The most commonly

used mineral oils and polyalpha-olefins

are not soluble with the refrigerant. They

must be separated with complex technology

and seriously limit the use of “direct expansion

evaporators” due to the deterioration in

the heat transfer.

Special demands are made on the thermal

stability of the lubricants due to the high

discharge gas temperatures. This is especially

valid when automatic operation is considered

where the oil is supposed to remain

in the circuit for years without losing any of

its stability.

NH3 has an extraordinarily high enthalpy difference

and thus a very small circulating

mass flow (approximately 13 to 15% compared

to R22). This feature, which is favourable

for large plants, makes the control of

the refrigerant injection more difficult with

small capacities.

A further criteria to be considered is the corrosive

action on copper containing materials;

pipe lines must therefore be made of steel.

The development of motor windings resistant

to NH3 is hindered, too. Another difficulty

arises from the electrical conductivity of the

refrigerant with higher moisture content.

Additional characteristics include toxicity and

flammability, which require special safety

measures for the construction and operation

of such plants.

Resulting design and

construction criteria

Based on the present “state of technology”,

industrial NH3 systems demand a completely

different plant technology, compared to

usual commercial systems.

Due to the insolubility with the lubricating oil

and the specific characteristics of the refrigerant,

high efficiency oil separators and

flooded evaporators with gravity or pump

circulation are usually employed. Because

of the danger to the public and to the product

to be cooled, the evaporator often cannot

be installed directly at the cold space

and the heat must be transported by a secondary

refrigerant circuit.

Due to the unfavorable thermal behaviour,

two stage compressors or screw compressors

with generously sized oil coolers must

be used even at medium pressure ratios.

Refrigerant lines, heat exchangers and fittings

must be made of steel; larger size

pipe lines must be examined by a certified


Depending upon the size of the plant and

the refrigerant charge, corresponding safety

measures and special machine rooms are


The refrigeration compressor is usually of

“open” design, the drive motor is a separate


These measures significantly increase the

expenditure for NH3 plants, especially for

medium and smaller capacities.

Efforts are therefore being made world-wide

to develop simpler systems which can also

be used in the commercial area.

A part of the research programs is dealing

with part soluble lubricants, with the aim of

improving oil circulation in the system. Simplified

methods for automatic return of nonsoluble

oils are also being examined as an


BITZER is strongly involved in these

projects and has a large number of

operating compressors. The experiences

up to now have revealed that

systems with partly soluble oils are difficult

to manage. The moisture content

in the system has an important influence

on the chemical stability of the

circuit and the wear of the compressor.

Besides, high refrigerant solution in the

oil (wet operation, insufficient oil temperature)

leads to strong wear on the

bearings and other moving parts. This

is due to the enormous volume change

when NH3 evaporates in the lubricated


These research developments are

being continued, with focus also on

alternative solutions for non-soluble


Various equipment manufacturers have

developed special evaporators, allowing

significantly reduced refrigerant charge.

There is a strong trend towards so-called

“low charge” systems, i.a. with regard to

safety requirements, which are also largely

determined by the refrigerant charge.

In addition to this, there are developments

for the “sealing” of NH3 plants: compact

liquid chillers (charge below 50 kg), installed

in a closed container and partly with

an integrated water reservoir to absorb NH3

in case of a leak. This type of compact unit

can be installed in areas which were previously

reserved for plants with refrigerants

of safety group A1 due to safety requirements.

Halogen free (natural) refrigerants


Halogen free (natural) refrigerants

Fig. 24 Comparison of discharge gas temperatures Fig. 25 NH3/R22 – comparison of pressure levels D

An assessment of NH3 compact systems –

instead of systems using HFC refrigerants

and conventional technology – is only possible

on an individual basis, taking into

account the particular application. From a

merely technical viewpoint and presupposing

an acceptable price level, a wider range

of products will supposedly become available

in the foreseeable future.

The product range from BITZER today

includes an extensive selection of optimized

NH3 compressors for various

types of lubricants:

o Single stage open reciprocating

compressors (displacement 19 to

152 m3/h with 1450 rpm) for air conditioning,

medium temperature and

booster applications

o Open screw compressors (displacement

84 to 1015 m3/h – with parallel

operation to 4060 m3/h – with 2900

rpm) for air conditioning, medium

and low temperature cooling.

Options for low temperature cooling:

– Single stage operation

– Economiser operation

– Booster operation

R723 (NH₃/DME) as

an alternative to NH3

The previously described experiences with

the use of NH3 in commercial refrigeration

plants with direct evaporation caused further

experiments on the basis of NH3 by

adding an oil soluble refrigerant component.

Main goals were improved oil transport and

heat transmission with conventional lubricants,

along with a reduced discharge gas

temperature for the extended application

range with single stage compressors.

The result of this research project is a refrigerant

blend of NH3 (60%) and dimethyl

ether “DME” (40%), It was developed by the

Institute of Air Handling and Refrigeration

(ILK) in Dresden, Germany, and has been

applied in a series of real systems. As a

largely inorganic refrigerant it received the

designation R723 due to it its average molecular

weight of 23 kg/kmol in accordance

to the standard refrigerant nomenclature.

Conversion of existing plants

The refrigerant NH3 is not suitable for the

conversion of existing (H)CFC or HFC

plants; they must be constructed completely

new with all components.

Supplementary BITZER information

concerning the application of NH3

(see also

o Technical Information KT-640

“Application of Ammonia (NH3)

as an alternative refrigerant”


DME was selected as an additional component

for its good solubility and high individual

stability. Its boiling point is -26°C, the

adiabatic exponent is relatively low, it is not

toxic and available in high purity. In the

abovementioned concentration NH3 and

DME form an azeotropic blend characterised

by a slightly higher pressure level than

pure NH3. The boiling point lies at -36.5°C

(NH3 -33.4°C), 26 bar (abs.) of condensing

pressure corresponds to 58.2°C (NH3


The discharge gas temperature in air conditioning

and medium temperature ranges

decreases by about 10 to 25 K (Fig. 24)

and allows for an extended application

range to higher pressure ratios. Thermodynamic

calculations conclude a single-digit

percent rise in refrigerating capacity compared

to NH3. The coefficient of performance

is similar and is even more favourable at

high pressure ratios, confirmed by experiments.

Due to the lower temperature level

during compression, an improved volumetric

and isentropic efficiency can be expected,

at least with reciprocating compressors in

case of an increasing pressure ratio.

Due to the higher molecular weight of DME,

mass flow and vapour density increase by

nearly 50% compared to NH3, although this

is of little importance to commercial plants,

especially in short circuits. In conventional

industrial refrigeration plants, however, this

is a substantial criterion with regard to pressure

drops and refrigerant circulation.

These considerations again show that the

preferred application area of R723 is in

commercial applications and especially in

liquid chillers.

Material compatibility is comparable to that

of NH3. Although non-ferrous metals (e.g.

CuNi alloys, bronze, hard solders) are

potentially suitable, provided minimum

water content in the system (< 1000 ppm),

a system design similar to typical ammonia

practise is recommended.

Mineral oils or (preferred) polyalpha olefin

are suitable lubricants. As mentioned be-

R290 (Propane) as

alternative refrigerant

R290 (propane) can also be used as a substitute

refrigerant. Being an organic compound

(hydrocarbon), it has no ozone

depletion potential and a negligible direct

global warming effect. To take into consideration

however, is a certain contribution to

summer smog.

Pressure levels and refrigerating capacity

are similar to R22, and its temperature

behaviour is as favourable as with R134a.

There are no particular problems with material.

In contrast to NH3, copper materials

are also suitable, so that semi-hermetic and

hermetic compressors are possible. Common

mineral oils of HCFC systems can be

used here as a lubricant over a wide application

range. Polyol esters (POE) and polyalpha-

olefins (PAO) offer even more favorable


Refrigeration plants with R290 have been in

operation world-wide for many years, mainly

in the industrial area – it is a “proven” refrigerant.

Meanwhile R290 is also used in smaller compact

systems with low refrigerant charges

like residential air-conditioning units and

heat pumps. Furthermore, a rising trend can

be observed in its use with commercial refrigeration

systems and chillers.

Propane is offered also as a mixture with

Isobutane (R600a) or Ethan (R170), in

order to provide a similar performance to

halocarbon refrigerants. Pure Isobutane is

mostly intended as a substitute for R12 in

small systems (preferably domestic refrigerators).

The disadvantage of hydrocarbons is their

high flammability, therefore they are classified

as refrigerants of “Safety Group A3”.

Based on the refrigerant charge quantities

commonly used in commercial systems, the

system design and risk analysis must be in

accordance with explosion protection regulations.

fore, the proportion of DME leads to improved

oil solubility and a partial miscibility.

Furthermore, the relatively low liquid density

and an increased DME concentration in the

oil enhances oil circulation. PAG oils would

be fully or partly miscible with R723 for typical

applications, but are not recommended

because of the chemical stability and high

solubility in the compressor crankcase

(strong vapour development in the bearings).

Tests have shown that the heat transfer

coefficient at evaporation and high heat flux

is improved in systems with R723 and mineral

oil compared to NH3 with mineral oil.

Further characteristics are toxicity and flammability.

The DME content lowers the ignition

point in air from 15 to 6%. However, the

azeotrope is ranked in safety group B2, but

may receive a different classification in case

of a revised assessment.

Resulting layout criteria

Experiences with the NH3 compact systems

described above can be used in plant technology.

However, the component layout has

to be adjusted considering the higher mass

flow. By appropriate selection of the evaporator

and the expansion valve, a very stable

superheat control must be ensured. Due to

the improved oil solubility,

wet operation”

can have considerable negative results

compared to NH3 systems with non-soluble


With regard to safety regulations, the same

criteria apply to installation and operation as

for NH3 plants.

Suitable compressors are special NH3 versions

which possibly have to be adapted to

the mass flow and the continuous oil circulation.

An oil separator is usually not necessary

with reciprocating compressors.

BITZER NH3 reciprocating compressors

are suitable for R723 in principle. An

individual selection of specifically adapted

compressors is possible on demand.

Halogen free (natural) refrigerants


Fig. 26 R290/R1270/R22 – comparison of performance data of a

semi-hermetic compressor

Fig. 27 R290/R1270/R22 – comparison of pressure levels

Semi-hermetic compressors in so-called

“hermetically sealed” systems are in this

case subject to regulations for hazardous

zone 2 (only seldom and short term risk).

Safety demands include special devices to

protect against excess pressures and special

arrangements for the electrical system. In

addition, measures are required to ensure

hazard free ventilation to effectively prevent

a flammable gas mixture in case of refrigerant


Design requirements are defined by standards

(e.g. EN378) and may vary in different

countries. For systems applied in the

EU, an assessment according to EC Directive

94/9/EC (ATEX) may become necessary

as well. With open compressors, this will

possibly lead to a classification in zone 1 ‒

which demands, however, electrical equipment

in special flame-proof design.

Resulting design criteria

Apart from the measures mentioned above,

propane systems require practically no special

features in the medium and low temperature

ranges compared to a usual (H)CFC

and HFC system. When sizing components,

however, the relatively low mass flow

should be considered (approximately 55 to

60% compared to R22). An advantage here

is that the refrigerant charge can be greatly

reduced. From the thermodynamic point of

view, an internal heat exchanger between

the suction and liquid line is recommended

as this will improve the refrigerating capacity

and COP.

Owing to the particularly high solubility of

R290 (and R1270) in common lubricants,

BITZER R290/R1270 compressors are

charged with special oil of a high viscosity

index and particularly good tribological


Again, an internal heat exchanger is of

advantage as it leads to higher oil temperatures,

lower solubility and therefore improved


Due to the very favourable temperature

behaviour (Fig. 25), single stage compressors

can be used down to approximately

– 40°C evaporation temperature. R290 could

thus also be considered as an alternative

for some of the HFC blends.

A range of ECOLINE compressors and

  1. compact screws is available for

R290. Due to the individual requirements

a specifically equipped compressor version

is offered. Inquiries and orders

need a clear reference to R290. The

handling of the order includes an individual

agreement between the contract partners.

Open reciprocating compressors

are also available for R290, together with

a comprehensive program of flame-proof

accessories which may be required.

Conversion of existing plants with R22

or HFC

Due to the special safety measures when

using R290, a conversion of existing systems

only seems possible in exceptional

cases. They are limited to systems, which

can be modified to meet the corresponding

safety regulations with an acceptable effort.

Supplementary BITZER information

concerning the use of R290

(see also

o Technical Information KT-660

“Application of Propane and Propylene

with semi-hermetic compressors”

Halogen free (natural) refrigerants


ever, tests by hydrocarbon manufacturers

and stability tests in real applications show

practically no reactivity in refrigeration systems.

Doubts have occasionally been

voiced in some literature regarding possible

carcinogenic effects of propylene. These

assumptions have been disproved by appropriate


Resulting design criteria

With regard to system technology, experience

gained from the use of propane can

widely be applied to propylene. However,

component dimensions have to be altered

due to higher volumetric refrigerating capacity

(Fig. 26). The compressor displacement

is correspondingly lower, as are the suction

and high pressure volume flows. Because

of higher vapour density, the mass flow is

almost the same as for R290. As liquid density

is nearly identical, the same applies to

the liquid volume in circulation.

As with R290, an internal heat exchanger

between suction and liquid lines is of

advantage. However, due to the higher dis-

Propylene (R1270) as an

alternative to Propane

For some time there has been increasing

interest in using propylene (propene) as a

substitute for R22 or HFC. Due to its higher

volumetric refrigerating capacity and lower

boiling temperature (compared to R290),

applications in medium and low temperature

systems are of particular interest, e.g. liquid

chillers for supermarkets. On the other

hand, higher pressure levels (> 20%) and

discharge gas temperatures have to be

taken into consideration, thus restricting the

possible application range.

Material compatibility is comparable to

propane, as is the choice of lubricants.

Propylene is also easily inflammable and

belongs to the safety group A3. The same

safety regulations are therefore to be

observed as with propane (page 31).

Due to the chemical double bond, propylene

reacts quite easily, risking polymerization at

high pressure and temperature levels. Howcharge

gas temperature of R1270, restrictions

are partly necessary at high pressure ratios.

A range of ECOLINE compressors and CS.

compact screws is available for R1270.

Due to the individual requirements a

specifically equipped compressor version

is offered. Inquiries and orders need a

clear reference to R1270.

The handling of the order includes an individual

agreement between the contract

partners. Open reciprocating compressors

are also available for R1270, together with

a comprehensive program of flame-proof

accessories which may be required.

Supplementary BITZER information

concerning the use of R1270

(see also

o Technical Information KT-660

“Application of Propane and Propylene

with semi-hermetic compressors”

Halogen free (natural) refrigerants


Fig. 28 R744(CO2) – pressure/enthalpy diagram

long periods. It should further be noted that

the heat transfer coefficients of CO2 are

considerably higher than of other refrigerants

– with the potential of very low temperature

differences in evaporators, condensers,

and gas coolers. Moreover, the

necessary pipe dimensions are very small,

and the influence of the pressure drop is

comparably low. In addition, when used as

a secondary fluid, the energy demand for

circulation pumps is extremely low.

In the following section, a few examples of

subcritical systems and resulting design criteria

are described. An additional section

provides details on transcritical applications.

Subcritical CO2 applications

From energy and pressure level points of

view, very beneficial applications can be

seen for industrial and larger commercial

refrigeration plants. For this, CO2 can be

used as a secondary fluid in a cascade system

and if required, in combination with a

further booster stage for lower evaporating

temperatures (Fig. 30).

were e.g. marine refrigeration systems. With

the introduction of the “(H)CFC Safety Refrigerants”,

CO2 became less popular and

had nearly disappeared by the 1950’s.

The main reasons for that are its relatively

unfavourable thermodynamic characteristics

for usual applications in refrigeration and air


The discharge pressure with CO2 is extremely

high, and the critical temperature at

31°C (74 bar) very low. Depending on the

heat sink temperature at the high pressure

side, transcritical operations with pressures

beyond 100 bar are required. Under these

conditions, energy efficiency is often lower

than in the classic vapour compression process

(with condensation), therefore the indirect

global warming effect is higher.

Nonetheless, there is a range of applications

in which CO2 can be used very economically

and with favourable eco-efficiency.

These include subcritical cascade plants,

but also transcritical systems, in which the

temperature glide on the high pressure side

can be used advantageously, or the system

conditions permit subcritical operation for

Carbon dioxide R744 (CO2)

as an alternative refrigerant

and secondary fluid

CO2 has had a long tradition in the refrigeration

technology reaching far into the 19th

century. It has no ozone depleting potential,

a negligible direct global warming potential

(GWP = 1), is chemically inactive, non-flammable

and not toxic in the classical sense.

Therefore, CO2 is not subjected to the stringent

containment demands of HFCs (F-Gas

Regulation) and flammable or toxic refrigerants.

However, compared to HFCs the

lower critical value in air has to be considered.

For closed rooms, this may require

special safety and detection systems.

CO2 is also low in cost and there is no

necessity for recovery and disposal. In addition,

it has a very high volumetric refrigerating

capacity: depending on operating conditions,

approx. 5 to 8 times as high as R22

and NH3.

Above all, the safety relevant characteristics

were an essential reason for the initial widespread

use. The main focus for applications

Halogen free (natural) refrigerants


The operating conditions are always subcritical

which guarantees good efficiency levels.

In the most favourable application

range (approx. -10 to -50°C), pressures are

still on a level where already available components

or items in development, e.g. for

R410A, can be matched with acceptable


Resulting design criteria

For the high temperature side of such a

cascade system, a compact cooling unit can

be used, whose evaporator serves on the

secondary side as the condenser for CO2.

Chlorine-free refrigerants are suitable, e.g.

NH3, HCs or HFCs, HFO and HFO/HFC


With NH3, the cascade heat exchanger

should be designed in a way that the dreaded

build-up of ammonium carbonate in the

case of leakage is prevented. This technology

has been applied in breweries for a

long time.

A secondary circuit for larger plants with

CO2 could be constructed utilising, to a

wide extent, the same principles for a low

pressure pump circulating system, as is

often used with NH3 plants. The essential

difference is the condensing of CO2 in the

cascade cooler, while the receiver tank

(accumulator) only serves as a supply vessel.

The extremely high volumetric refrigerating

capacity of CO2 (latent heat through the

changing of phases) leads to very low mass

flow rates, allows for small cross sectional

pipe and minimal energy needs for the circulating


There are different solutions for the combination

with a further compression stage, e.g.

for low temperatures.

Fig. 30 shows a variation with an additional

receiver, which one or more booster compressors

will bring down to the necessary

evaporation pressure. Likewise, the discharge

gas is fed into the cascade cooler,

condenses and is carried over to the receiver

(MT). The feeding of the low pressure

receiver (LT) is achieved by a level control

device. Instead of conventional pump circulation

the booster stage can also be built as

a so-called LPR system.

The circulation pump is thus not necessary,

but the number of evaporators is then limited

with view to an even distribution of the

injected CO2.

In the case of a system breakdown where a

high rise in pressure could occur, safety

valves can vent the CO2 to the atmosphere

with the necessary precautions. As an alternative,

additional cooling units for CO2 condensation

are also used where longer shutoff

periods can be bridged without a critical

pressure increase.

For systems in commercial applications, a

direct expansion version is possible as well.

Supermarket plants with their usually widely

branched pipe work offer an especially

good potential in this regard: The medium

temperature system is carried out in a conventional

design or with a secondary circuit,

for low temperature application combined

with a CO2 cascade system (for subcritical

operation). A system example is shown in

Fig. 31.

For a general application, however, not all

requirements can be met at the moment. It

is worth considering that system technology

changes in many respects and specially adjusted

components are necessary to meet

the demands.

Fig. 31 Convention al re friger ati on system combined with CO2 l ow

tempe rature cascade

Halogen free (natural) refrigerants


an intermediate pressure receiver. Depending

on the temperature curve of the heat

sink, a system designed for transcritical

operation can also be operated subcritically

‒ with higher efficiency. In this case, the

gas cooler becomes the condenser.

Another feature of transcritical operation is

the necessary control of the high pressure

to a defined level. This “optimum pressure”

is determined as a function of gas cooler

outlet temperature by means of balancing

between the highest possible enthalpy difference

and at once minimum compression

work. It must be adapted to the relevant

operating conditions using an intelligent

modulating controller (see system example,

Fig. 32).

As described before, under purely thermodynamic

aspects, the transcritical operating

mode appears to be unfavourable in terms

of energy efficiency. In fact, this is true for

systems with a fairly high temperature level

of the heat sink on the high pressure side.

However, additional measures can improve

efficiency, such as the use of parallel compression

(economiser system) and/or ejectors

or expanders for recovering the throttling

losses during expansion of the


Apart from that, there are application areas

in which a transcritical process is advantageous

in energy demand. These include

heat pumps for sanitary water or drying processes.

With the usually very high temperature

gradients between the discharge temperature

at the gas cooler intake and the

heat sink intake temperature, a very low

gas temperature outlet is achievable. This is

facilitated by the temperature glide curve

and the relatively high mean temperature

difference between CO2 vapour and secondary

fluid. The low gas outlet temperature

leads to a particularly high enthalpy difference,

and therefore to a high system COP.

Low-capacity sanitary water heat pumps are

already manufactured and used in large

quantities. Plants for medium to higher

capacities (e.g. hotels, swimming pools,

drying systems) must be planned and

realised individually. Their number is therefore

still limited, but with an upward trend.

Apart from these specific applications, there

is also a range of developments for the

classical areas of refrigeration and air-conditioning,

e.g. supermarket refrigeration.

Installations with parallel compounded compressors

are in operation to a larger scale.

They are predominantly booster systems

where medium and low temperature circuits

are connected (without heat exchanger).

The operating experience and the calculated

energy costs show promising results.

However, the investment costs are still

higher than for conventional plants with

HFCs and direct expansion.

On the one hand, the favourable energy

costs are due to the high degree of optimized

components and the system control,

as well as the previously described advantages

regarding heat transfer and pressure

drop. On the other hand, these installations

are preferably used in climate zones permitting

very high running times in subcritical

operation due to the annual ambient temperature


For increasing the efficiency of CO2 supermarket

systems and for using them in

warmer climate zones, the technologies

described above using parallel compression

and/or ejectors are increasingly used.

Therefore, but also because of very

demanding technology and requirements for

qualification of planners and service personnel,

CO2 technology cannot be regarded as

a general replacement for plants using HFC


Resulting design criteria

Detailed information on this topic would go

beyond the scope of this publication. In any

case, the system and control techniques

are substantially different from conventional

plants. Already when considering pressure

levels as well as volume and mass flow

ratios specially developed components,

controls, and safety devices as well as suitably

dimensioned pipework must be provided.

The compressors, for example, must be

properly designed because of the high

vapour density and pressure levels (particularly

on the suction side). There are also

specific requirements with regard to materials.

Furthermore only highly dehydrated

CO2 must be used.

High demands are made on lubricants as

well. Conventional oils are mostly not miscible

and therefore require costly measures

to return the oil from the system. On the

other hand, if miscible and highly soluble

POE are used, the viscosity is strongly

reduced. Further information to lubricants

see page 40 and Fig. 37, page 44.

For subcritical CO2 applications BITZER

offers two series of special compressors.

Supplementary BITZER information concerning

compressor selection for subcritical

CO2 systems

(see also

o Brochure KP-120

Semi-hermetic reciprocating compressors

for subcritical CO2 applications

(LP/HP standstill pressures up to

30/53 bar)

o Brochure KP-122

Semi-hermetic reciprocating compressors

for subcritical CO2 applications

(LP/HP standstill pressures up to

100 bar)

o Additional publications on request

Transcritical CO2 applications

Transcritical processes are characterized in

that the heat rejection on the high pressure

side proceeds isobar but not isotherm.

Contrary to the condensation process during

subcritical operation, gas cooling (desuperheating)

occurs, with corresponding

temperature glide. Therefore, the heat

exchanger is described as gas cooler. As

long as operation remains above the critical

pressure (74 bar), only high-density vapour

will be transported. Condensation only

takes place after expansion to a lower pressure

level – e.g. by interstage expansion in

Halogen free (natural) refrigerants


The compressor technology is particularly

demanding. The special requirements result

in a completely independent approach. For

example, this involves design, materials

(bursting resistance), displacement, crank

gear, working valves, lubrication system, as

well as compressor and motor cooling.

Hereby, the high thermal load severely limits

the application for single-stage compression.

Low temperature cooling requires

2-stage operation, whereby separate high and

low pressure compressors are particularly

advantageous with parallel compounded


The criteria mentioned above in connection

with subcritical systems apply to an even

higher degree for lubricants. For further

information to lubricants see page 40 and

Fig. 37, page 44.

Further development is necessary in various

areas, and transcritical CO2 technology

cannot in general be regarded as state-ofthe-


CO2 in mobile

air-conditioning systems

Within the scope of the long-discussed

measures for reducing direct refrigerant

emissions, and the ban on the use of

R134a in MAC systems within the EU, the

development of CO2 systems has been

pursued intensively since several years.

At first glance, efficiency and therefore indirect

emissions from CO2 systems under

typical ambient conditions appear to be

unfavourable. But it must be considered

that present R134a systems are less efficient

than stationary plants of the same

capacity, because of specific installation

conditions and high pressure losses in

pipework and heat exchangers. With CO2,

pressure losses have significantly less influence.

Moreover, system efficiency is further

improved by the high heat transfer coefficients

in the heat exchangers.

This is why optimized CO2 air conditioning

systems are able to achieve efficiencies

comparable to those of R134a. Regarding

the usual leakage rates of such systems, a

more favourable balance is obtained in

terms of TEWI.

From today’s viewpoint, it is not yet possible

to make a prediction as to whether CO2 can

in the long run prevail in this application. It

certainly also depends on the experience

with “low GWP” refrigerants that have been

introduced by the automotive industry (see

chapter “Low GWP” HFO refrigerants

R1234yf and R1234ze(E), page 11). Further

aspects such as operating safety, costs,

and global logistics will play an important


Fig. 32 Example of a transcritical CO2 Booster system

?? ??


For transcritical CO2 applications,

BITZER offers a wide range of special

compressors. Their use is aimed at specific

applications, therefore individual

examination and assessment are


Suplementary BITZER information concerning

compressor selection for transcritical

CO2 systems

(see also

o Brochure KP-130

Semi-hermetic reciprocating compressors

for transcritical CO2 applications

o Additional publications upon request



Halogen free (natural) refrigerants


R124 and R142b

as substitutes for

R114 and R12B1

In place of R114 and R12B1 previously

used in high-temperature heat pumps and

crane air conditioning systems, HCFCs

R124 and R142b can still be used as alternatives

in most regions outside of the EU.

With these gases it is also possible to use

long proven lubricants, preferably mineral

oils and alkyl benzenes with high viscosity.

Because of their ozone depleting potential,

these refrigerants will only be an interim

solution. In the EU member states, the

application of HCFCs is no longer allowed.

For R124 and R142b the same restrictions

are valid as for R22 (page 8). The flammability

of R142b and the resulting safety

implications should also be considered

(safety group A2).

Resulting design criteria/

Converting existing plants

Compared to R114, the alternatives have

lower boiling temperatures (approx. -10°C),

which results in larger differences in the

pressure levels and volumetric refrigerating

capacities. This leads to stronger limitations

in the application range at high evaporating

and condensing temperatures.

Converting an existing installation will in

most cases necessitate the exchange of the

compressor and control devices. Owing to

the lower volume flow (higher volumetric

refrigerating capacity), adjustments to the

evaporator and the suction line may be


Over the previous years BITZER compressors

have been found to be well

suited with R124 and R142b in actual

installations. Depending on the application

range and compressor type modifications

are necessary, however. Performance

data including further design

instructions are available on request.

Chlorine free substitutes for

special applications

Due to the limited market for systems with

extra high and low temperature applications,

the development of alternative refrigerants

and system components for these has

been pursued less intensely.

In the meantime, a group of alternatives for

the CFC R114 and Halon R12B1 (high temperature),

R13B1, R13 and R503 (extra low

temperature) have been offered as replacements.

On closer examination, however, the

thermodynamic properties of the alternatives

differ considerably from the previously

used substances. This can cause costly

changes especially with the conversion of

existing systems.

Alternatives for R114

and R12B1

R227ea and R236fa are considered suitable

substitutes even though they may no longer

be used in new installations in the EU from

2020, due to their high GWP.

R227ea cannot be seen as a full replacement.

Although tests and experience in real

plants show favorable results, a critical temperature

of 102°C limits the condensing

temperature to 85..90°C with conventional

plant technology.

R236fa provides the more favourable conditions

at least in this regard – the critical

temperature is above 120°C. A disadvantage,

however, is the lower volumetric refrigerating

capacity. It is similar to R114 and

40% below the performance of R124, which

is widely used for extra high temperature

applications today.

R600a (Isobutane) will be an interesting

alternative where safety regulations allow

the use of hydrocarbons (safety group A3).

With a critical temperature of 135°C, condensing

temperatures of 100°C and more

are within reach. The volumetric refrigerating

capacity is almost identical to R124.

The “Low GWP” refrigerant R1234ze(E) can

also be regarded as a potential candidate

for extra high temperature applications

(page 24). Compared to R124, its refrigerating

capacity is 10 to 20% higher, its pressure

level about 25% higher. At identical

refrigerating capacities, the mass flow differs

only slightly. Its critical temperature is

107°C, which would enable an economical

operation up to a condensing temperature

of about 90°C. Though, like R1234yf,

R1234ze(E) has low flammability and therefore

classified into the new safety group

A2L. The corresponding safety regulations

must be observed.

As no sufficient operating experience is

available so far, the suitability of this refrigerant

for long-term use cannot be assessed


For high temperature heat pumps in process

technology and special applications at

high temperatures, Chemours has presented

an HFO-based refrigerant called OpteonTM

MZ (R1336mzz(Z)). Its critical temperature

is 171°C, the boiling temperature

33.1°C. This enables an operation at condensing

temperatures far above 100°C for

which only purpose-built compressors and

system components can be used.

R1336mzz(Z) has a GWP < 10 but is not

flammable according to tests. This means a

classification in safety group A1.

A more detailed evaluation is not yet possible

with respect to the chemical stability of

the refrigerant and of the lubricants at the

very high temperatures and the usually very

long operating cycles of such systems. The

special applications also include cogeneration

systems – the so-called “Organic

Rankine Cycle” (ORC) – which become

increasingly important. In addition to

R1336mzz(Z) as a potentially suitable operating

fluid, a series of other substances

are also possible, depending on the temperature

level of the heat source and the

heat sink.

Refrigerants for special applications


Fig. 33 R13B1/HFC alternatives – comparison of discharge gas temperatures

of a 2-stage compressor

in their construction accordingly. For

several years BITZER has been involved

in various projects and has already

gained important knowledge with this

technology and experience in design and


A comprehensive description of ORC

systems would go beyond the scope of

this Refrigerant Report. Further information

is available upon request.

Alternatives for R13B1

Besides R410A, ISCEON® MO89 (DuPont)

can be regarded as potential R13B1 substitute.

For R410A, a substantially higher discharge

gas temperature than for R13B1 is

to be considered, which restricts the application

range even in 2-stage compression

systems to a greater extent.

ISCEON® MO89 has been used for many

years, preferably in freeze-drying plants.

Meanwhile, production has ceased. However,

for historical reasons the refrigerant will

continue to be included in this Report. It is a

mixture of R125 and R218 with a small proportion

of R290. Due to the properties of

the two main components, density and

They include R245fa (GWP = 1050) having

a critical temperature of 154°C, which like

R1336mzz(Z) is also suitable as refrigerant

for chillers with large centrifugal compressors.

Solvay offers further refrigerants for ORC

applications, containing the base component

R365mfc. A product with the trade

name Solkatherm® SES36 already presented

several years ago contains perfluoropolyether

as a blend component. It is an

azeotropic blend with a critical temperature

of 178°C. Meanwhile two zeotropic blends

containing R365mfc and R227ea have been

developed whose critical temperatures are

177°C and 182°C, due to different mixing

ratios. They are available under the trade

names Solkatherm® SES24 and SES30.

In ORC systems zeotropic behavior may be

advantageous. In the case of single-phase

heat sources and heat sinks, the temperature

difference at the so-called “pitch point”

can be raised by the gliding evaporation

and condensation. This leads to improved

heat transmission due to the higher driving

average temperature difference.

As an expander for ORC systems screw

and scroll compressors can be adapted

mass flow are relatively high, and discharge

gas temperature is very low. Liquid

subcooling is of particular advantage.

Both of the mentioned refrigerants have

fairly high pressure levels and are therefore

limited to 40..45°C condensing temperature

with the usually applied 2-stage compressors.

They also show less capacity

than R13B1 at evaporating temperatures

below -60°C.

In addition to this, the steep fall of pressure

limits the application at very low temperatures

and may require a change to a cascade

system with e.g. R23, R508A/B or

R170 (ethane) in the low temperature


Lubrication and material compatibility are

similar to other HFC blends.

The EU F-Gas Regulation (Annex III) provides

an exemption “for applications

designed to cool products below -50°C”.

This means that even after 2020, refrigerants

with GWP > 2500 can be used in new

plants. Due to the “phase-down” however,

quantities will be limited, resulting in a considerable

increase in price and very limited


It is therefore imperative to develop alternative

solutions for which, however, no

overall recommendation is possible. Twostage

compressors may be operated e.g.

with R448A/449A (safety group A1) or

R1270 (A3) down to an evaporation temperature

of -60..- 65°C. Although R404A/

R507A alternatives with GWP < approx.

250 (safety group A2L) are potentially possible,

so far only limited experience has

been gained even for typical low temperature


At evaporating temperatures of down to

-50..-52°C, operation with CO2 is also

possible − either in a two-stage or a cascade


However, each variant generally requires a

specific design and laboratory tests.

Refrigerants for special applications


Refrigerants for special applications

Alternatives for R13

and R503

For these substances, the situation is still

quite favorable from a purely technical

point of view; they can be replaced by R23

and R508A/R508B. R170 (ethane) is also

suitable if the safety regulations allow a

flammable substance (safety group A3).

Due to the partly steeper pressure curve of

the alternative refrigerants and the higher

discharge gas temperature of R23 compared

to R13, differences in performance

and application ranges for the compressors

must be considered. Heat exchangers and

controls have to be adapted individually.

As lubricants for R23 and R508A/B, polyol

ester oils are suitable, but must be

matched for the special requirements at

extreme low temperatures.

R170 is also well soluble with conventional

oils, but an adaptation to the temperature

will be necessary.

Applications with these refrigerants are

purely for cooling products below -50°C.

Hence, the exemption described in the previous

chapter in the EU F-Gas Regulation

applies in particular.

For R23 and R508A/B, however, the

effects of “phase-down” are particularly

serious. The GWP values range from

13200 to 14800 (AR4). Even relatively

small quantities are therefore very much at

the expense of the available quotas.

Apart from R170 (ethane) with the special

safety precautions required for A3 refrigerants,

there are no directly comparable

alternatives for R23 and R508A/B within

the group of HFOs or HFO/HFC mixtures

(safety groups A1 or A2L). In many cases,

however, the use of A3 refrigerants is not

possible or would involve unjustifiable

expenses and high costs in the relevant

special applications.

Following these challenges, research projects

have been initiated, in which the use

of N2O (nitrous oxide) and mixtures of N2O

and CO2 are examined in more detail.

Extensive examinations and tests at the

Karlsruhe University of Applied Sciences

and the Institute of Air Handling and Refrigeration

(ILK) in Dresden show revealing


N2O (R744A) has similar thermodynamic

properties and pressures as CO2, identical

molecular weight, a very low triple point

(-90.8°C) and a critical temperature of

36.4°C. The GWP is 298, which is a fraction

of the R23 and R508A/B values. In

sum, an ideal alternative for special applications

up to about -80°C evaporating temperature?

At first glance, these are very positive features.

Unfortunately, there are also negative

aspects that virtually preclude the use

of N2O as a pure substance.

Pure N2O as a refrigerant is a safety risk: It

has a narcotic effect and promotes fire.

N2O can oxidize other substances. In addition,

under specific conditions (pressure,

temperature or ignition source), exothermic

decomposition reactions can occur, which

fundamentally call into question the permanently

safe operation of a refrigeration

system with pure N2O.

By adding CO2 in higher percentages (over

approx. 15%), the triple point is slightly

shifted towards higher temperatures, but at

the same time a positive effect (“phlegmatization”)

on oxidation and chemical decomposition

is achieved. The safety risk is

reduced significantly, and material compatibility

is considerably improved. Nevertheless,

there are special challenges i.a. for

lubricants with a high resistance to oxidation

which must also be suitable for the

special requirements at low temperature


Investigations are ongoing. A final assessment

is not yet possible, which is why no

guidelines can currently be drawn up for

the design and implementation of such


BITZER has carried out investigations

and also collected experiences with

several of the substitutes mentioned.

Performance data and instructions are

available on request. Due to the individual

system technology for these special

installations, consultation with

BITZER is necessary.



Lubricants for compressors

Positive displacement compressors ‒ as

are predominantly used in commercial and

industrial refrigeration, air conditioning and

heat pump systems ‒ are commonly oillubricated.

Despite appropriate constructional

measures and/or installation of an oil

separator, a small amount of oil is pumped

into the circuit together with the compressed

gas flow. To stabilise the oil balance,

suitable measures for continuous oil return

must be taken. Oils that are soluble and

miscible with the refrigerant are advantageous.

The refrigerant dissolved in the oil significantly

reduces the viscosity, improving

oil fluidity and minimising the negative

influence on heat transfer in heat exchangers.

In the past, so-called naphthenic mineral

oils and synthetic alkylbenzenes were preferred.

For systems with CFC and HCFC

refrigerants (for example R22) and hydrocarbons,

they are very favorable with

regard to solubility and miscibility. On the

other hand, owing to their low polarity, they

are insufficiently miscible with the highly

polar HFC and HFO refrigerants and are

therefore not properly and sufficiently

drawn into the refrigeration cycle.

Immiscible oils can accumulate in the heat

exchangers and hinder the heat transfer so

much that operation of the system is no

longer possible.

Therefore, new lubricants with appropriate

solubility/miscibility have been developed

for systems with HFC and HFO refrigerants.

These are oils based on polyol ester

(POE) and polyalkylene glycol (PAG).

They have similar or better lubricating properties

than previously customary oils, but

are more or less hygroscopic, depending

on the refrigerant solubility. This requires

special care in manufacturing (including

drying), transport, storage and charging, so

that chemical reactions in the plant – such

as hydrolysis in POE – are avoided.

PAG-based oils are particularly critical concerning

water absorption. In addition, they

have a relatively low dielectric strength and

are therefore less suitable for semi-hermetic

and hermetic compressors. They are

primarily used in mobile air conditioning

systems with open drive compressors,

where special requirements for lubrication

and best solubility/miscibility are required

because of a high oil circulation rate. To

avoid copper plating, non-ferrous metals

are used in these systems.

The remaining refrigeration industry so far

prefers POE oils. The extensive experience

gained with them is positive if the water

content in the oil does not significantly

exceed 100 ppm. However, only oils specified

by the compressor manufacturer may

be used. Because of the increased reactivity

of HFOs with oil, this is especially true

for systems with these refrigerants.

Compressors for factory-made air conditioners

and chillers are also increasingly

being charged with polyvinyl ether (PVE)

oils. Although they are more hygroscopic

than POE, they are very resistant to hydrolysis,

thermally and chemically stable, have

good lubricating properties and high dielectric

strength. In contrast to POE, they are

less prone to the formation of metal soaps

and thus offer more security against blokkage

of capillaries.

Special requirements for the lubricants

exist with CO2 systems. Specially formulated

POEs are also suitable for use in widely

ramified pipe networks due to their particularly

good solubility/miscibility. However,

these properties have a negative effect on

viscosity and lubricity (tribology) and therefore

require compressors with an extremely

robust and wear-resistant drive gear. At

very high loads, e.g. heat pumps, PAG oils

specially developed for CO2 applications

ensure even more favorable lubrication


Due to the thermodynamic properties of

ammonia (NH3) and the resulting plant

engineering, non-soluble/miscible oils are

advantageous. These include for example

mineral oils and polyalphaolefins (PAO).

However, they require a special technique

for oil separation and oil recirculation. For

further explanation as well as additional

information on applications when using partially

soluble PAG oils see chapter NH3

(Ammonia) as alternative refrigerant (page

28) and supplementary information (see


Further information see Fig. 37 “Overview

lubricants”, page 44 and explanations for

the particular refrigerants.

Supplementary BITZER information concerning


(see also

o Technical Information KT-500

„Refrigeration oil for reciprocating

compressors with (H)CFC or NH3”

o Technical Information KT-510

„Polyolester oils BSE32 and BSE55 for

BITZER reciprocating compressors“

o Technical Information KT-640

„Application of Ammonia (NH3) as an

alternative refrigerant” – chapter:

“Lubricants and their influence on the

system design”

o Technical Information KT-660

„Use of propane (R290) and propene

(R1270) in semi-hermetic BITZER

compressors” – chapter: “Lubricants”

o Operating Instructions KB-120 and


„Semi-hermetic reciprocating compressors

for CO2 applications“

o Manuals for screw compressors

SH-100 to SH-500 – chapter: „Lubricants”

Further information see Fig. 37 Lubricants

for compressors, page 44 and explanations

for the particular refrigerants.

AR4: according to IPCC IV – time horizon 100 years –

also basis for EU F-Gas Regulation 517/2014

AR5: according to IPCC V – time horizon 100 years

N/A Data not yet published.

Alternative refrigerant has larger deviation in

refrigerating capacity and pressure

Alternative refrigerant has larger deviation

below -60°C evaporating temperature

Also used as a component in R290/

600a-Blends (direct alternative to R12)

Classification according to EN 378-1

and ASHRAE 34

According to EN 378:2016





1 6


These data are valid subject to reservations; they are based on information published by various refrigerant manufacturers.

Tab. 6 Refrigerant properties (continued on Tab. 7)


Refrigerant properties






























R513A (XP10)

R450A (N-13)

R448A (N-40)

R449A (XP40)
















































R502 (R12 )

R114 , R12B1

R12 (R500)

R13 (R503)



R404A, R507A

R22 (R13B1 )


R22 (R502)

R404A (R22)

R404A (R22)


R404A (R22)

R404A (R22)



R12B1, R114


R12 (R22 )

mainly used as

part components

for blends

R410A (R22)

HFC Single-component Refrigerants

Valid for single stage compressors

Data on request (operating conditions

must be given)

Triple point at 5.27 bar

Stated performance data are average values

based on calorimeter tests.

Rounded values

Total glide from bubble to dew line –

based on 1 bar (abs.) pressure.

Real glide dependent on operating


Approx. values in evaporator:

H/M 70%; L 60% of total glide

Reference refrigerant for these values

is stated in Tab. 6 under the nomination

“Substitute for” (column 3)

Letter within brackets indicates

operating conditions

H High temp (+5/50°C)

M Medium temp (-10/45°C)

L Low temp (-35/40°C)


Tab. 7 Refrigerant properties

3 4





Refrigerant properties

R2 2

R1 24

R1 42b



























R513A (XP1 0)

R450A (N-13)

R448A (N-40)

R449A (X P4 0)