Refrigerant r600a (isobutane) properties, characteristics, working pressure, features

R600a (isobutane, chemical formula C4H10) is a refrigerant, a flammable gas with a boiling point of -11.7 °C at 1 atm. It is applied in refrigerating household and commercial equipment. It is a cheap alternative to R134a refrigerant. Also found under the names and trademarks:

  • HC-600A;
  • GU-600a
  • Methylpropane;
  • 2-methylpropane;
  • CARE 10;
  • Refrigerant-600a.

In this article we will talk about the R600a refrigerant, the characteristics, properties, and features of this refrigerant. You will learn about its features, expediency of application, pluses and minuses. At the end of the article you will find tables with the physical and chemical characteristics of R600a gas, its working pressure.

What is refrigerant R600a or isobutane

Refrigerant R600a (isobutane, HC-600a) – natural gas. It has zero potential for the destruction of the Earth’s ozone layer and minimal impact on the greenhouse effect. It is an alternative to obsolete refrigerant R12.

The chemical formula of r-600a refrigerant is similar to butane, natural gas. Butane is R600 refrigerant. The prefix in the name iso- means that with the same chemical composition, gas molecules have a different structure. This is indicated by the letter “a” in the classification of the refrigerant.

Schematic representation of butane (R600) and isobutane (R600a) molecules
On the left is an isobutane molecule, on the right is a butane molecule. Dark balls correspond to carbon atoms, light balls correspond to hydrogen atoms.


Due to its good performance, R600a (HC 600a) has been used in refrigerators since the early 20th century. After the advent of the R12 refrigerant, isobutane was no longer used due to the fact that it required a lot, 200-400 grams in one household refrigerator.

In large volumes, r600a gas was flammable in such quantities. In the event of a leak, it could ignite from open flames, electrical sparks and cause a fire. For decades, isobutane was forgotten.

In the 20th century, refrigeration technology was constantly improved. By the 1990s, a household refrigerator system needed no more than 150 grams of isobutane to operate. In addition, after the signing of the Montreal Protocol, R12 refrigerant began to be withdrawn from circulation. Isobutane has become the main refrigerant for household refrigeration and freezing equipment.

Production of R600a, isobutane (n-butane)

Refrigerant R600a is obtained by rearranging butane molecules (R600). This process is called isomerization. The number of hydrogen and carbon atoms is preserved in the molecule, but their geometric structure changes.

Butane isomerization takes place in a butamer plant using a catalyst made of platinum or other rare earth metals. In the process, only part of the gas is converted to n-butane. The resulting mixture is passed through a distillation deisobutanization column, in which R600a is separated from R600.

Butamer plant
Butamer plant Honeywell.

Physical properties of refrigerant R600a, isobutane

R600-a is a colorless, odorless gas. It has a low boiling point, which allows it to be used in climate and cooling technology. It does not contain chlorine and fluorine, unlike gases such as R12 and R134a.

Refrigerant gas R600a is flammable. When storing, transporting and using it, safety precautions must be observed. Under high pressure, its ignition temperature decreases. 5.45 kg of isobutane is pumped into a conventional refrigerant cylinder, 2.5 times less than r134a (tetrafluoroethane) or r12.

The raw material for the production of isobutane is natural gases extracted from the bowels of the Earth. It can be obtained from products of oil refining, cracking, and other hydrocarbon conversion processes.

Due to its characteristics, r600a is used as a component of R406a, R413A, R414A, R414B, R422A, R422B, R422C, R422D, R422E, R424A, R428A, R429A, R430A, R434A R439A, R436A, R431A, R44.

Interesting fact

Isobutane is often used as a filler in aerosol cans, lighters and lighter refills.

Advantages of R600a refrigerant

  1. Refueling a household refrigerator requires 25 to 150 grams of gas. This is less than in equipment operating on other types of refrigerants.
  2. Isobutane is cheaper than other refrigerants.
  3. R600a provides high cooling capacity. The most economical household refrigerators of classes A +, A ++, A +++ work on it.
  4. The production of isobutane is not associated with complex chemical processes. O available and cheap.
  5. Refrigerant R600-a is chemically stable and does not react with metals, rubbers and plastics.
  6. Isobutane refrigeration uses cheap mineral oil rather than expensive synthetic oil.
  7. Due to the smaller amount of gas in the refrigerator system, the noise level is reduced.

Cons of refrigerant R600a

  1. When leaking, isobutane can ignite from fire, electrical discharge, sparks.
  2. The gas is colorless, odorless. Therefore, it is impossible to determine the leak without special equipment or inspection of the refrigerator.
  3. When transferring equipment to another refrigerant, it will need to be modified, the compressor oil, possibly the compressor, will need to be replaced.

Features of isobutane

Compared to other refrigerants, R600a has a higher cooling capacity. For the full operation of the equipment, it requires less. Therefore, the cost of the components of the refrigeration circuit is reduced. This leads to cheaper home appliances.

When replacing refrigerant r12 with r600, no major modifications to the equipment are required. It is only necessary to change the filter-drier and build up the capillary tube. The cost of this upgrade is minimal. Given the difference in the price of r12 and r600a gases, the transportation of a refrigerator to isobutane is quite justified.

A small spark is enough to ignite isobutane. Gas ignites if its content in the air leaves from 14 to 85 cubic meters. cm per liter, or from 31 to 205 grams. At a different concentration, it will not light up. But there is not much of it in refrigerators, so the likelihood of a fire is minimal, although it exists.

With a small leak, the gas will burn in the immediate vicinity of the leak. If it comes out all at once and ignites, it will immediately flare up and burn out. In this case, the fire will not be able to spread to other objects.

Many sites steal this quote from each other without thinking about its meaninglessness:

Modern designs of domestic and commercial refrigeration equipment contain an acceptable concentration of R600. The dose of filling household refrigerators with isobutane is so small that it practically cannot lead to a fire: with a complete leak of the refrigerant from the unit, its concentration in a kitchen with a volume of 20 cubic meters will be ten times lower than the flammability threshold.

Probably, the authors of the articles did not teach physics at all for high school. Isobutane tends to accumulate at the bottom of the room. Its concentration will vary with altitude. If the room is not ventilated and there is a leak, at a certain height from the floor, the ratio of isobutane to air will be within the explosive limits .

The statement that r600a refrigerant is dangerous is false. Isobutane is not toxic or poisonous. Poisoning can only occur at very high concentrations in the air. When leaking from a household refrigerator, it is absolutely safe.

Due to the safety and chemical stability, R600a refrigerant does not need to be disposed of. When the system is repaired or transferred to another refrigerant, the remaining old gas is simply vented into the atmosphere.

Interesting fact

Special requirements are imposed on refrigeration equipment designed to use isobutane as a refrigerant. It is designed in such a way that if there is a leak in the place where the gas accumulates, it cannot be ignited. There are no electrical or electronic components capable of igniting the gas.

Refrigerant r600a, specifications

Characteristics R600aMeaning
Molecular (molar) mass, g/mol58.12
Molecular formulaС4Н10
Boiling point at 0.1 MPa, ºС-11.73
Freezing point at 0.1 MPa, ºС-159.6
Flash point, °С-85
Density at 25ºС, g/cc0.551
Evaporation pressure at 25°C, MPa0.498
Critical temperature, °С135
Critical pressure, MPa3.65
Critical density, g/cc0.221
Latent heat of vaporization, kJ/kg366.5
Explosive limits of volume fraction in air, %1.8 – 8.4
Air-mixture cooling efficiency, J/g150.7
Solubility in oilComplete
Volume of saturated liquid, l/kg0.844
Ozone depletion potential, ODP0
Greenhouse potential, GWP0
Annual Greenhouse Potential, HGWP0.001
CAS number75-28-5

The following impurities are possible in isobutane in negligible amounts: methane, ethane, water, propane, propylene, N-butane, pentene, butene-1, isobutylene, isopentane, N-pentane, carbon dioxide, sulfur, nitrogen, oxygen.

Suction working pressure r600a in refrigerator

t, °СAbs., barRel., bart, °СAbs., barRel., bar

Requirements for the purity of refrigerant R600a according to AHRI 700

Appearancevisually transparent
Solid particlesvisually clean
Isobutane contentover 99.5%
The sum of all impuritiesup to 0.5%
Water contentless than 10ppm
Acidityless than 1ppm
The content of gaseous refrigerant in the containerup to 0.01%

* ppm, parts per million (English) – parts per million.

Refrigerant R600a research results

Impact on human health

In case of contact with eyes, frostbite may occur due to rapid evaporation of the substance. Skin contact with rapid evaporation may cause frostbite. Manifested in a change in skin color from white to gray, the formation of blisters.

Isobutane is heavier than air and can cause asphyxiation due to reduced breathing air. This can lead to loss of consciousness and death. Preliminary effects can be:

  • Dizziness;
  • Disorientation;
  • vomiting or nausea;
  • sleepy state;
  • Violation of cardiovascular activity.

Storage and transportation

R600a refrigerant is sold in three versions:

  • 420 mg refill cartridges;
  • Cylinders 5.45/6.5 kg;
  • Gas cylinders of 50 kg;
  • Isotank (special container) 600kg.

During transportation and storage, the container must not be heated. It is unacceptable to store isobutane near heat sources, open driving, electrical appliances in order to avoid ignition due to leakage. When working with gas, it is recommended to use personal protective equipment, goggles and gloves.

In the publication, we talked about what is isobutane, R600a refrigerant, what are its characteristics, physical properties. We hope the article was helpful. If you have questions or want to express your opinion – do it in the comments. Don’t forget to save it to your wall and share it on social networks.

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