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.
If refrigerant migration occurs in a system that has a crankcase heater, the vapor will be forced away from the crankcase and end up in the suction line. This refrigerant may condense in the suction line and cause slugging in the compressor’s cylinders on startup.
Remember, when wiring motors for a certain voltage, the service technician must always refer to the motor manufacturer’s literature and numbering scheme before wiring the motor for the desired voltage or damage to the motor’s windings may occur.
Voltage unbalances exceeding more than 2 percent in three-phase systems can cause current unbalance among the windings. These voltage and current unbalances can cause an increase in winding temperature and an overheating problem that can be detrimental to the motor.
This article explores some of the new, state-of-the-art, digital, wireless technologies available for measuring system superheat and subcooling. These new tools enable technicians to automate measurements, share data, and save time and money