Articles by John Tomczyk

Hydrofluorocarbon (HFC)-134a replaced chlorofluorocarbon (CFC)-12. Now, 134a is on its way out, too. The July 2, 2015, ruling from the U.S. Environmental Protection Agency (EPA) set forth the time frames for the phasedown of certain HFC refrigerants in specific applications.

One of the main components of any refrigeration or air conditioning system is the condenser. As its name indicates, the condenser condenses refrigerant vapor sent to it from the compressor. However, the condenser also performs other important functions, too. 

An undercharge of refrigerant will cause low head and suction pressures, but that is not the only thing that will cause both pressures to be low. An undercharge will have low condenser liquid subcooling readings on the high side, where a dirty air filter for the evaporator will not produce low condenser liquid subcooling readings.

Diagnosing an air conditioning system isn’t easy. A service technician must be a trained professional to diagnose a system efficiently and correctly — no longer can a tech rely on rules of thumb for coil temperatures or pressures. 

Checking temperatures in and out of the air conditioning coil is an important part of preparing a residential air conditioning system for the season. This article will cover how checking temperatures through an evaporator coil can tell a service technician if there’s a problem in the air-handling system or refrigerant system. It will also cover other general troubleshooting areas.

Compressor performance curves can provide a service technician with the Btu pumping rate (capacity), mass flow rates, operating amperage, and operating wattage of a compressor when the suction pressure and head pressure are known for the system. 

A refrigeration system’s compression or pressure ratio is defined as the absolute discharge pressure divided by the absolute suction pressure. Calculating this ratio can be a big help when it comes to troubleshooting a system.

It’s very important to follow all safety procedures and retrofit guidelines when retrofitting a system with a refrigerant blend. By all means, never try to blend any refrigerants yourself because dangerous conditions and personal injury can occur.

Last month’s article covered a 400-series refrigerant blend’s total temperature glide, effective temperature glide, fractionation, superheat, subcooling, and average evaporator and condensing temperatures using a pressure/temperature chart. This article deals with system pressure drops and net temperature glide in a refrigeration and/or air conditioning system.