Use and Precautions of R32 Refrigerant

R32 refrigerant is a new type of refrigerant. It is a flammable and explosive refrigerant with unstable chemical properties, but the harm to the environment is still very small, so we discuss some precautions for R32.

1. R32 Refrigerant Basic Properties

The chemical name of R32 refrigerant is difluoromethane, and the molecular formula is CH2F2. Difluoromethane is a coolant with zero ozone depletion potential, a gas at room temperature, and a colorless transparent liquid under pressure. It is easily soluble in oil but hardly soluble in water.

R32 refrigerant is one of the replacements for R22. The ozone-depleting potential (ODP) of R32 refrigerant is 0, the global warming coefficient value (GWP) is 0.11, and the working pressure is the same as that of R410A. Under the same cooling capacity, the charging amount of R32 is only about two-thirds of that of R22. Compared with R290, R32 has only low flammability. Compared with R410A, the global warming coefficient of R32 is only about one-third of the former. These advantages make it one of the main substitutes for R22, with the most potential. R32 is energy-saving, green, and does not harm the ozone layer. It has also become one of the new refrigerants of modern refrigerants.

Difluoromethane is a coolant with zero ozone depletion potential. Difluoromethane and pentafluoroethane can form an azeotropic mixture (called R-410A), which is used as a replacement for chlorofluorocarbons (also known as Freon) in new coolant systems, mainly replacing HCFC-22, as a compound medium and low temperature mixed refrigerant. Although it has zero ozone depletion potential, it has a high global warming potential, 550 times that of carbon dioxide on a per 100-year time basis.

2. Simple Comparison of R22, R410A, R32 Refrigerant and R290

1) R22: Refrigerant to be phased out. The chemical composition of R22 is chlorodifluoromethane (CHClF2), which is non-flammable, non-explosive, and has low toxicity. The safety level belongs to A1. The ozone depletion potential of R22 is ODP>0, so it is unsuitable for long-term use.

2) R410A: Alternative refrigerant to R22. R410A is composed of R32 refrigerant and R125 with a mass fraction of 50% each, of which R32 refrigerant (difluoromethane CH2F2, A2L), R125 (pentafluoroethane CF3CHF2, A1), and the safety level of A410A are A1, which also belongs to non-combustible, non-flammable Explosive, very little toxic working fluid.

Compared with R22, R410a is a high-pressure refrigerant, which has higher requirements on the compressive strength of equipment and systems, but it is beneficial to reduce the displacement of compressors, reduce the diameter of heat exchange copper tubes, and save raw materials; the heat transfer and flow characteristics of R410a Better than R22, it is beneficial to improve the operating efficiency of the air conditioner, and the energy saving effect is obvious. It has been widely used at present.

The ODP of R410a=0 does not deplete ozone. Still, the global warming potential of R410a is GWP=1730 (for comparison, GWP=1 of CO2), which has a greater effect on global warming, so R410A is not the ultimate environmentally friendly refrigerant solution.

3) R290. The chemical composition of R290 is propane (CH3CH2CH3), with low toxicity and flammability, and the safety level is A3. The explosion limit of R290 is 2.1% ~ 10.0% [3], and the explosion point is much lower than that of R32.

ODP=0 and GWP=20 of R290 have very little effect on global warming. It belongs to natural organic matter and can be obtained directly from low-priced petroleum-liquefied gas. R290 has good thermal performance, large latent heat of vaporization, and less liquid filling in the system. Under the same working conditions, the exhaust temperature can be 20°C lower than that of R22, which is beneficial to prolong the service life of the compressor.

4) R32 refrigerant. The chemical composition of R32 refrigerant is difluoromethane CH2F2, which is very toxic and slightly flammable, and its safety level is A2L. R32 has the possibility of explosion, and its explosion limit is 14.4% ~ 29.3% [3]. It is necessary to solve the problem of low flammability in the application of household air conditioners.

The refrigeration performance of R32 refrigerant is close to that of R410a. Under the same cooling capacity, the filling amount of R32 is less than that of R410a (about 30% less), but the exhaust temperature is higher than that of R410a. ODP=0, GWP=675 of R32, belongs to the green environmental protection refrigerant and is an important substitute for R22.

3. R32 Refrigerant Regular Filling Method

1) Turn on the cooling mode and set the wind speed at the highest wind speed position. Measure the temperature of the air outlet after 10 minutes. The lower the temperature, the better. It is generally considered that the refrigerant needs to be replenished if it is higher than 15 degrees (the air outlet temperature will vary due to weather changes. The difference is that there is no standard air outlet temperature value and the general experience judges that it is between 8–15 degrees.

2) Looking at it with the eyes, the air outlet blows out white mist-like wind, which looks very cold, but the actual temperature is not low, and the effect is not good, which is a sign of a slight shortage of refrigerant, and it is enough to add a little refrigerant.

3) Still check to see if there is frost or icing at the connection pipe interface of the outdoor unit. If there is, it means that there is a lack of refrigerant and needs to be replenished; for normal air conditioners, both the thick and thin pipes are wet.

4) Measure the pressure of the low-pressure pipe. The normal fixed-frequency air conditioner’s refrigeration pressure is 4.5–5 kg. The refrigerant needs to be replenished if it is lower than this figure. The method of adding R32 refrigerant to the refrigeration system pipeline is the same as that of ordinary R22.

Precautions:

The method of adding r32 refrigerant to the refrigeration system is the same as our commonly used r22, but r32 is flammable and explosive. It must keep away from the fire source before refilling.
When filling r32, the air conditioner must stop. Otherwise, it will damage the air conditioner. Generally, r22 is used in air conditioners, but R32 is flammable and explosive, so please pay special attention to keeping away from it during the filling process. It is best to refill an ignition source without the air conditioning unit running.

4. Several Maintenance Precautions for R32 Refrigerant

1) Maintenance place
Smoking is strictly prohibited in the maintenance process, fire or heat sources are prohibited in the operating area within two meters, and maintenance while smoking is strictly prohibited.

2) Precautions for pipeline maintenance of R32 refrigerant internal unit
The inner connecting pipe of the R32 split unit cannot disassemble, so when the indoor unit system needs to be returned to a professional outlet for maintenance, the anti-disassembly nut must destroy.

3) Refrigerant recovery
It is strictly forbidden to determine the closing time of the large valve based on experience, dismantle the outdoor unit or move the machine to recover the refrigerant. The recovery time is greatly affected by the operating frequency of the unit, the operating wind speed, and the climate. After the system is under negative pressure, if there is a leak on the low-pressure side, air will be sucked in, posing a major safety hazard.

4) Check the hose
Air tightness check (confirm that each pressure gauge hose is well sealed).
The correct method of operation: Check the tightness of each connection point after tightening each hose to ensure a good seal

5) Welding
Strictly implement the correct operation method of welding operation specification. Operating requirements: The operator must hold the welder operation certificate issued by the national labor department. Gas and oxygen cylinders should keep away from fire sources and high-temperature sunlight.

6) Additional refrigerant

• It is strictly forbidden to add refrigerant by feeling. At this time, the high operating pressure rises, and the low pressure becomes negative. There is a hidden danger of air inhalation in the system, and the temperature of the compressor shell rises.
• It is strictly forbidden to unplug the external fan or fully cover the condenser to check for blockage and leaks. It is required to use additional quantitative refrigerant for charging.
  It is strictly forbidden to use inferior or fake refrigerants.
• Some maintenance personnel are greedy for cheap and buy cheap refrigerants on the market. Cheap refrigerants may be fake refrigerants. Mixing highly flammable substances such as methane and R40 is not ruled out, and the system’s possibility of combustion and explosion increases.

R32 refrigerant is a new type of environmentally friendly refrigerant, but it is flammable and explosive, so it must use with more attention and standardized operation, such as:

• Do not buy low-quality refrigerants or fake refrigerants (fake refrigerants may be mixed with highly flammable substances such as methane and R40, which will increase the possibility of combustion and explosion in the system).
• Do not use the wrong refrigerant (mixed or misused refrigerants of different working fluids).
• Standardize the operation of the installation and maintenance links (to avoid leakage and air intake in each operation link).
  For R32 products, heat sources are prohibited within 2 meters for maintenance and discharge of refrigerant, and a vacuum must be drawn.
• It is strictly forbidden to start up and run when the system is blocked (the valve is not opened or the indoor unit is not connected).
• Ensure sufficient safety distance for maintenance welding, use brand welding tools, pressure vessels must have a tempering device, and do well in nitrogen protection and standard operation for welding.
• For poor cooling effect and irregular failure (the compressor can work), determine whether the static pressure is within the safe range and then operate according to regulations.