John Tomczyk is HVACR professor emeritus, Ferris State University, Big Rapids, Michigan, and coauthor of Refrigeration & Air Conditioning Technology, published by Cengage Learning. Contact him at email@example.com.
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.
System design, performance, and service conditions must be evaluated when retrofitting with a zeotropic or near-azeotropic refrigerant blend. Always follow the refrigerant manufacturer’s retrofit guidelines before retrofitting with any refrigerant, or system performance could be affected and/or injury may occur.
Using variable frequency drives (VFDs) to control the speed of a compressor can provide improved occupant comfort and quieter operation in air conditioning and heat pump applications. Always consult with the specific compressor manufacturer before using a VFD controller on any compressor.