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.

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.