Notes on refrigerants
CONTENTS
Refrigerant function ............................................................................................................... 2
Primary refrigerants .............................................................................................................. 2
Secondary refrigerants .......................................................................................................... 2
Ideal Properties of Refrigerants ............................................................................................. 2
Safety Group Classifications ................................................................................................. 3
Terminology .......................................................................................................................... 3
Identification of Refrigerants.................................................................................................. 4
Characteristics of refrigerants ............................................................................................... 5
High pressure R410A refrigerant: .......................................................................................... 6
R410A Procedures and Equipment: ...................................................................................... 7
Review questions .................................................................................................................. 8
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REFRIGERANT FUNCTION
A refrigerant is a substance used in refrigeration systems to absorb heat in the evaporator,
by changing state from a liquid to a vapour and rejects this heat in the condenser as it
changes back to a liquid. Refrigerants can be classed as primary or secondary refrigerants.
PRIMARY REFRIGERANTS
Primary refrigerants are substances that change twice (once in the evaporator and once in
the condenser) and produce refrigeration (cooling) by vaporisation. Primary refrigerants
transfer the bulk of the heat through a latent heat process.
SECONDARY REFRIGERANTS
Secondary refrigerants absorb heat and change temperature in order to transfer heat from
the substance or product to be cooled. They usually do not change state in the cooling cycle
but change temperature by absorbing sensible heat. A good example of a secondary
refrigerant is chilled water.
IDEAL PROPERTIES OF REFRIGERANTS

high latent heat to produce large refrigerating effect in the cycle of operation

low boiling point at atmosphere pressure so as to be able to produce low temperatures

low condensing temperature at relatively low head pressure

high critical temperature

low specific volume of vapour per kilowatt of refrigeration

no corrosive action on metals used

a chemical compound that will be stable under all working conditions

non flammable and non explosive

no odour and non poisonous

easy to detect leaks in the system

no affinity to moisture, so that no gases or acids will be formed affecting system
operation

no reaction with lubricants used.
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SAFETY GROUP CLASSIFICATIONS
A = Low toxicity.
B = High toxicity.
1 = Low flammability.
2 = Medium flammability.
3 = High flammability.
Group A1 refrigerants are the least hazardous, group B3 the most hazardous.
Group A1 – common refrigerants: R11, R12, R22, R134a, R500.
Group B1 – common refrigerants: R123, R764.
Group B2 – common refrigerants: R40, R611, R717.
TERMINOLOGY

Azeotrope – consists of a mixture of two (2) or more chemical compounds. They form a
new refrigerant with its own properties, do not separate and have a constant saturation
temperature. Charging can be either as a liquid or as a vapour.

Temperature glide – occurs when the evaporating (or condensing) temperature changes
during the vaporisation (boiling or condensation) process, due to the composition
changes that occur in blend refrigerants. Temperature glide should be checked when
choosing a replacement refrigerant.

Zeotropic (Blends) – is a new refrigerant made from two (2) or more different refrigerants
(blends). They are a mixture of volatile substances, which change in composition as they
evaporate. Evaporating temperature changes (Glide) as the more volatile component
distils out of the less volatile components. MUST be liquid charged. Examples include
the R400 family.
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IDENTIFICATION OF REFRIGERANTS
Refrigerants are identified by:

trade name or number

chemical name or formula

ANSI / ASHRAE standards

AS 4484 colour code.
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CHARACTERISTICS OF REFRIGERANTS
Condensing and boiling
temperatures
These determine the range of selection and eliminate a large
number of the possible liquids. The boiling point for the
temperature required may be too high to produce the low
temperature desired, or it may require a very low pressure
(high vacuum) to produce the low temperature. A high
boiling point on the suction side requires a vacuum for
operating at low temperatures. A very low boiling point
usually requires a very high head pressure to produce
condensation.
Latent heat value of
refrigerant
Latent heat should be high for the change of state at the
boiling point. The higher the latent heat, the less refrigerant
required to be circulated per kilowatt of refrigeration.
Type/temperature of
condensing medium
Mediums used frequently are water and air.
Displacement volume of the
compressor
The size of the compressor needed can dictate the choice of
refrigerant to be used. Some refrigerants require large
compressor capacity because the refrigerants they
compress are received at very low pressures. Density of the
vapour should be high. The refrigerant used should not
require a pressure below atmospheric pressure to produce
the refrigerating temperature.
Toxicity or poisonous action
Refrigerants may pose a health hazard from lethal poisoning
(chemical substance being taken into the blood stream) or
from suffocation (refrigerants are generally heavier than air
and precautions should be taken in confined spaces).
Flammability and
explosiveness
These factors carry considerable weight in the selection of
refrigerant from the standpoint of the fire risk.
Most volatile gases containing hydrogen are flammable and
some become highly explosive when broken down or subject
to temperatures above 38 °C in the presence of carbon
compounds. These refrigerants often have environmental
advantages over the ‘safer’ refrigerants and with correct
training and compliance with safety standards, they can be
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used successfully.
Odour
Odour might be desirable in finding leaks in a system, but if
the odour has a bad effect on an individual, then it becomes
a disadvantage. Some toxic refrigerants are odourless and in
these cases material having a strong odour such as
ammonia is introduced into the refrigerant to inform
operators that a leak has occurred.
Stability of gas
Stability of gas is very desirable. A refrigerant should not
decompose at any temperature that may be encountered in
the system – otherwise losses and possibly serious
operating effects may result.
Corrosive action on metals
The effect of refrigerants on structural metals of the system
is important as ammonia, for example, cannot be used with
copper or copper alloys.
However, copper can be used with fluorocarbon refrigerants.
Effect on lubricating oil
The refrigerant must not form destructive compounds,
destroy lubricating properties, nor solidify or congeal at low
temperatures with oil.
Critical temperature
The temperature above which a gas cannot be condensed
into a liquid by increasing the pressure.
The temperature at which the liquid flashes into a vapour
without the addition of latent heat.
The highest temperature to which the liquid can be raised
under any pressure and still remain a liquid.
Non-hazardous
This assumes that the refrigerant is non toxic, non irritating,
non flammable, non explosive, not hazardous to stored food
or other products and will not cause a fire hazard if a large
leak occurs.
Environmental properties
A refrigerant should have a zero or low Ozone Depletion
Potential (ODP), a low Global Warming Potential (GWP) and
a short atmospheric life.
HIGH PRESSURE R410A REFRIGERANT:
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
R410A is a zero ozone-depleting (ODP) refrigerant, as it doesn’t contain chlorine to
damage the ozone layer.

Its pressures are approximately 60% higher (1.6 times) than R22.

R410A is a zeotropic refrigerant and is made up of R32 (50%) and R125 (50%).
R410A PROCEDURES AND EQUIPMENT:

R410A is only used in units designed for R410A use and is not to be used for retrofitting
existing systems.

Due to higher pressures R410A requires dedicated specialised cylinders, gauges, lines
and recovery equipment.

R410A uses synthetic POE oil, as do all HFC refrigerants, and is hygroscopic (absorbs
moisture).

Being a zeotropic refrigerant R410A has differential leakage rates and must be liquid
charged.

Follow manufacture’s installation instructions when using R410A and ensure compliance
with Australian acts, regulations and codes.

Only authorised technicians are to install or service systems designed for R410A.
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REVIEW QUESTIONS
1. What is the function of a refrigerant substance? See page 2.
2. What do primary refrigerants do? See page 2.
3. What do secondary refrigerants do? See page 2.
4. What are the characteristics of refrigerants I need to remember? See pages 3 and 4.
5. What are the ideal properties of refrigerants? See page 5.
6. What are the four (4) ways I can identify refrigerants? See page 6.
7. What are four (4) safety group classifications? See page 7.
8. What do these words mean? See page 8
a. azeotrope
b. zeotropic blends
c. temperature glide.
9. List three (3) important points about R410A refrigerant. See page 8.
10. List six (6) important points about R410A procedures and equipment. See page 8.
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