Hydrocarbon Refrigerant Data


Direct Environmental Impacts
Boiling Point
Dipole Moment
Chemical Stability
Electrical Properties
Molecular Mass
Thermodynamic and Transport Properties
Emergency Procedures

Direct Environmental Impacts

The Ozone Depletion Potential of hydrocarbon refrigerants is zero and the Global Warming Potential relative to carbon dioxide is three for all integration periods twenty years or over. Hydrocarbons replace fluorocarbons like CFCs, HCFCs and HFCs which have high environmental impacts and often poor refrigerant performance.

Air, ammonia, carbon dioxide and water have lower direct environmental impacts than hydrocarbons and are equally or more acceptable as replacements for fluorocarbons in suitable applications.

Boiling Point

For systems operating with given temperatures, as vapour pressure increases the cooling capacity, torque and electric current draw all increase. Boiling point at standard atmospheric pressure (101325 Pa) is a measure of vapour pressure at a given temperature. A satisfactory replacement refrigerant will have a boiling point close to the original refrigerant. The boiling points of the pure hydrocarbon refrigerants which occur naturally are:
Refrigerant 170 290 600a 600 601a 601
Boiling point deg C -88.8 -42.1 -11.6 -0.5 27.8 36.1
Molecular mass g/mol 30.1 44.1 58.1 58.1 72.1 72.1

Synthetic hydrocarbons are often more expensive than natural hydrocarbons. Those below are used as replacement refrigerants only when a pure chemical with their boiling point is essential to the system design.
Chemical propene cyclopropane neopentane cyclopentane
Refrigerant 1270 C270 601b? C601?
Boiling point deg C -47.7 -32.9 9.5 49.3
Molecular mass g/mol 42.1 42.1 72.1 70.1

Mixtures of hydrocarbon refrigerants are zeotropic and may match the vapour pressure of any refrigerant with a boiling point between them. Three mixtures have become well established commercially, R601/601a [50/50], R290/600a [50/50] and R170/290 [6/94]. The values in square brackets are the percentage composition by mass of the respective refrigerant in the mixture and are omitted where no confusion will occur. Always charge zeotropic refrigerant mixtures as liquids.

The hydrocarbon (HC) refrigerants on the bottom line of the following table are substituted for the refrigerants in the first three lines:
CFC 502 - 12 11 -
HCFC - 22 406a - 123
HFC - - 134a - -
HC 170/290 290 290/600a 601/601a 601

Please contact a hydrocarbon refrigerant supplier for information on which of their products match the above hydrocarbon refrigerant numbers and how suitable they are as replacements in a particular application.

For centrifugal chillers, R601/601a with an electronic 38% increase in rotor speed replaces 11 and R601 with a 42% increase in rotor speed replaces 123.

In redesigned small equipment, R12 and 134a are often replaced by 600a, thinner metal and compressors with higher dimensionless specific speed. The dimensionless specific speed of the compressor is then much closer to one giving higher efficiency. The additional energy saving from higher specific speed is typically 5%.

Dipole Moment

Hydrocarbon refrigerants have low or zero dipole moment so their liquids are non-polar. This means they are miscible with all organic oils including natural and synthetic hydrocarbons, polyol esters (POE) and polyalkylene glycols (PAG). It is not necessary to change either the oil or the drier when changing to hydrocarbon refrigerant. Hydrocarbon oils are however recommended for use with hydrocarbon refrigerants because they absorb less moisture, are less flammable, are chemically more stable and have better lubricating properties.

Chemical Stability

The presence of small amounts of water and air in fluorocarbon refrigerants can form acids which corrode and damage valves. With hydrocarbons this cannot occur because halogen atoms are not present.

The compatibility of hydrocarbon refrigerants with hoses and sealants is similar to that of R12.

At the temperatures occurring in refrigeration circuits, the natural hydrocarbon refrigerants, 170, 290, 600a, 600, 601a, 601 and their mixtures are very stable so they do not form gums or tars. The synthetic hydrocarbon refrigerants, 1270, C270 and C601, are unsaturated and may form gums and tars with the oil under some conditions.

Electrical Properties

The compatibility of hydrocarbon refrigerants with electrical insulating materials is similar to that of R12. The electrical insulating properties of hydrocarbon refrigerants are high and the dielectric constant low.

Molecular Mass

Hydrocarbon refrigerants have a lower molecular mass than fluorocarbons of the same boiling point. This gives them lower density and viscosity and higher thermal conductivity than the fluorocarbons. These properties result in lower pressure loss and higher heat transfer coefficient. Energy consumption calculated from thermodynamic data and ideal cycles alone differs little for hydrocarbon and fluorocarbon refrigerants. When transport properties and real cycles are included the calculated advantage of hydrocarbon refrigerants is substantial which laboratory equipment tests confirm.

Typical energy savings when hydrocarbons replace fluorocarbons and cooling capacity remains the same are:
Capacity kW Saving Causes
Below 1 15% lower pressure loss, higher specific speed and heat transfer
From 1 to 100 10% lower pressure loss, higher heat transfer
Over 100 5% higher heat transfer

Thermodynamic and Transport Properties

Skeletal tables for refrigerants 170/290 [6/94], 290, 290/600a [50/50], 600a, 600, 601a and 601 may be viewed in plain ASCII from this website. For 290/600a [50/50] a chart is available in PostScript (tm) hc12chrt.ps or Adobe's PDF hc12chrt.pdf. The tables and chart were prepared using various versions of REFPROP from the National Institute of Standards and Technology. URL http://www.nist.gov/srd describes REFPROP or NIST Standard Reference Database 23 and how you may order the latest version.

When heating a liquid slowly at a given pressure, the first temperature at which large bubbles of vapour will grow is the bubble point. Refrigerant liquid is at the bubble point for its measured pressure if its half-full container is fully immersed in a bath at a constant temperature below room until thermal equilibrium. Bubble point data lines for each pressure are marked with a final L in the tables.

When cooling a vapour slowly at a given pressure, the first temperature at which large drops of liquid will grow is the dew point. Dew point data lines for each pressure are marked with a final V and are immediately below the bubble point line in the tables.

The difference between the dew and bubble point temperatures at a given pressure and composition is the temperature glide. Temperature glide is zero for pure substances like refrigerants 170, 290, 600a, 600, 601a and 601. The temperature glide is almost 10 K for some zeotropic mixtures like 170/290 and 290/600a. Counter or cross flow of refrigerant and fluid gives lower energy consumption than parallel flow for such glides.

The temperature difference of a superheated vapour above its dew point temperature at a given pressure is called superheat. Two values of superheat are given in the tables, 20 and 40 K. Each superheat line is marked with a final V and can be distinguished from the other vapour lines at the same pressure by examining the temperature in the second column.

Textbooks on thermodynamics and refrigeration and air conditioning discuss the use and meaning of physical quantities in the tables like entropy and enthalpy. The tables require linear interpolation and if this is inconvenient please purchase the REFPROP program from NIST.


All oils and refrigerants are dangerous. The principal hazards are: explosion, fire, asphyxiation or poisoning, flying metal, corrosion or chemical reaction and chemical or cold burns. All oils and refrigerants require safety measures to prevent hazards causing injury to persons or damage to property. The safety measures depend on the mass of the oil and refrigerant, the design of the system and the individual properties of the oils and refrigerants. Complying with the provisions of refrigerant safety standards, like BS 4434-1995, should make all oils and refrigerants equally safe.

Hydrocarbon refrigerants are highly flammable. For the natural hydrocarbon refrigerants 170, 290, 600a, 600, 601a and 601 and their mixtures representative flammability data for initial temperature 25 deg C and pressure 101325 Pa are:
Lower explosive limit 34 g/kg air
Upper explosive limit 170 g/kg air
Stochiometric mixture 62 g/kg air
Flame speed 0.4 m/s
Flame temperature 2240 deg C
Heat of combustion 50 MJ/kg

Further safety data and information can be found in the literature.


Among the many necessary precautions in refrigerant safety standards include the following:-

*Weigh cylinder or measure liquid volume while charging. Do not exceed the charge recommended by the refrigerant supplier. A hydrocarbon refrigerant charge is typically one third the mass of a fluorocarbon charge.

*Do not light cigarettes while charging refrigerant or searching for refrigerant leaks.

*Do not use compressed air for leak testing refrigerant circuits. Use dry nitrogen or other inert gas.

*Have appropriate equipment for extinguishing fires available while servicing plant. A carbon dioxide fire extinguisher is recommended as water is not safe for electrical fires.

*Flameproof electrical equipment is necessary near charges of hydrocarbon refrigerant over 1 kg.

*If the charge of hydrocarbon refrigerant exceeds 250 g and 8 g/m^3 enclosed space, explosion venting is necessary. Venting should keep the overpressure from a refrigerant explosion below 2 kPa. The door windows of a motor car bend outwards to relieve overpressure satisfactorily. The ducting on a totally enclosed plantroom is often insufficient to relieve overpressure. Floor to ceiling louvres to the outside with wall area 20% or greater of the plantroom floor area should be sufficient.

Emergency Procedures

Please add the following emergency procedures to those required by legislation and standards:-

*If a major refrigerant release occurs, shut off the cylinder valve if charging, evacuate the room and leave doors and windows open and ventilation fans on. Return after refrigerant odour disappears and/or gas alarms cease.

*If oil mist or released refrigerant is ignited immediately evacuate the room and then return with appropriate equipment to extinguish fires.

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