When working on a refrigeration system, technicians may occasionally come across one where the type of refrigerant is unknown. Either the system’s data plate is missing or unreadable, or the refrigerant has been changed out and the system has not been properly identified with the replacement refrigerant. Do not panic right away. Although this is an issue, the current system problem may not require knowing the refrigerant type. The failure might be electrical in nature or a maintenance issue such as a dirty coil.
However, if it becomes necessary to measure the system’s pressures and temperature to properly troubleshoot the failure, it can be a major issue. Without knowing the refrigerant type, how do technicians determine the current operating evaporating temperature, condensing temperature, evaporator superheat, and the condenser’s subcooling? It may not be possible to determine if the system has lost some refrigerant, or if the compressor is pumping properly, or any other system issue that would cause a change in its operating pressures and temperatures.
So, what can a technician do?
If the system has never been serviced, or if there is some assurance that the original refrigerant type is still in the system, it may be possible to determine the refrigerant type by looking at the compressor or metering device. The compressor’s specifications will indicate the original type of refrigerant designed for the compressor; however, many compressors can be used with multiple refrigerants, so this might not be helpful. If the system uses a thermostatic expansion valve (TXV), the same is true; however, some TXVs are also designed to be used with multiple refrigerants, so once again, not helpful.
If the system has been serviced previously, and it is believed the original refrigerant type has been changed, it becomes extremely difficult to determine the refrigerant currently being used. Perhaps using a pressure/temperature analysis can helpful? But probably not, as some refrigerants have similar pressure/temperature characteristics, and it may not be possible to tell if the refrigerant is at saturation where its pressure and temperature are being measured.
Again, what can a technician do?
If the system uses a relatively small amount of refrigerant, recover it, and treat the recovered refrigerant as a contaminated or mixed refrigerant. Then replace it with either the original refrigerant if possible, or a replacement refrigerant suitable to be used with the compressor and metering device. If the system uses a relatively large amount of refrigerant, simply replacing it may not be a wise economical decision. It is possible to send out a sample of the refrigerant to be analyzed — not a fast solution, but one where a large amount of refrigerant would not be wasted.
To avoid this difficult and potentially very costly scenario, always remember to mark or label the system with its refrigerant type if it is being changed out. Mark it in several locations so it is easily seen, and do not leave the next technician (which could be you) to have to work on a system with an unknown refrigerant.