What are the Operating Precautions for Combustible Refrigerants R32 and R290 ?

The world is looking for an alternative to R22 refrigerant, but there has been little real progress. Each on the so-called “environmentally friendly” refrigerant, either toxic, or is explosive, or is low efficiency and expensive. Related manufacturers and supporting compressor tech is also relatively lagging behind, the introduction of R32, R290 refrigerant more or less hidden dangers, we hope this article on R32, R290 refrigerant characteristics will help you.

Characteristics of R32 refrigerant

  • Full name: Difluoromethane
  • Molecular formula: CH2F2
  • Physical properties: Colorless, odorless, slightly combustible (A2 level).

R32 has similar thermodynamic properties to R410A.

R32 refrigerant

Characteristics of R290 refrigerant

  • Full name: Propane
  • Molecular formula: C3H8
  • Appearance and properties: colorless gas, odorless in pure form.
  • Solubility: slightly soluble in water, soluble in ether, ethanol.
  • Flash point (°C): -104.
  • Upper explosion limit % (V/V): 9.5.
  • Lower explosion limit % (V/V): 2.1.

NOTE: Flash point: the temperature at which the first flash of a mixture of vapour and air on the surface of a combustible liquid occurs in contact with fire.

R290 refrigerant

Comparison of Refrigerant Physical Properties

R22 R410A R290 R32
ODP 0.05 0 0 0
GWP 1700 2100 <20 675
Toxicity No No No No
Combustibility A1 A1 A3 A2
Filling volume (relative to R22) 1 0.8 0.45 0.7

Advantages and disadvantages relative to HFC

Refrigerant Molecular GWP ODP
R290 C3H8 3 0
R32 CH2F2 580 0
R410A R32/R125 1900 0
R22 CHF2Cl 1700 0.055

Classification of commonly used refrigerants by safety level

R290 R32 R22 R410A R134a
Lower flammable limit vol% 2.1 13.5 NA NA NA
kg/m3 0.038 0.306 NA NA NA
Automatic ignition temperature 470 648 635 N.D. 743
Minimum ignition energy mJ 0.31 30-100 NA NA NA
Burning velocity cm/s 46 6.7 NA NA NA
Heat of combustion MJ/kg 50.3 9.4 2.2 -4.4 4.2
Occupational exposure limit PPMv 1000 1000 1000 1000 1000
Safety class(ASHRAE34) A3 A2 A1 A1 A1

R32 Summary

R32 refrigerant’s global warming factor is 1/3 of R410A, and is more environmentally friendly than traditional R410A and R22 refrigerants, but R32 has some flammability.

Compared with R410A refrigerant, R32 saturation pressure is about 3% higher, exhaust temperature is about 8-15℃ higher, power is about 3-5% higher and energy efficiency ratio is about 5% higher.

Under the same working condition and the same operating frequency of the compressor, the refrigeration capacity and energy efficiency of R32 system is about 5% higher than that of R410A refrigerant.

R290 Summary

  • Health hazard: simple asphyxiation and anesthesia. Brief human exposure to 1 % propane causes no symptoms, concentrations below 10 % cause only mild dizziness, exposure to high concentrations may result in anesthesia and loss of consciousness, very high concentrations may cause asphyxiation.
  • Hazardous characteristics: flammable gas, mixed with air can form explosive mixtures, the risk of combustion and explosion when exposed to heat sources and open flames.

The amount of R290 refrigerant is only 40%~55% of R22 and R410a, which is less and more economical.

The low freezing point and greater latent heat of evaporation make the cooling speed faster per unit time, the isentropic compression ratio does less work, which makes the compressor work easier and extends the service life of the compressor; the small molecular weight and good fluidity make the delivery pressure lower and reduce the load of the compressor. Using R290 refrigerant, the energy saving rate can reach 15~35%.

Precautions for use of R32, R290 refrigerants

When welding in the user’s home, combustible materials are strictly prohibited within 2 meters of the working site. In case of accidental large leakage of refrigerant, prompt ventilation is required, taking care not to introduce ignition sources.

When the refrigeration system needs to replace parts in maintenance, the machine must be vacuumed before burning welding operation.

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