The PENN Quick Response Expansion Valve (QREV) is an electronically controlled expansion valve used in air conditioning, heat pumps, and refrigeration applications.
The QREV and Precision Superheat Controller (PSHC) form an electronically controlled expansion valve solution that maximizes evaporator efficiency. Users achieve energy savings by reaching targeted superheat faster and controlling the valve more precisely, through varying load conditions. The silicon-based microelectromechanical system (MEMS) technology eliminates valve wear. There are no stepper motor failures associated with this type of technology. The PSHC comes loaded with 17 user selectable approved refrigerants for easy commissioning, plus it has an on-board pressure sensor. The wiring harness, which completes the kit, includes a temperature sensor for sensing the suction line temperature.
Base valve selection on the QREV capacity rating at specific system conditions. Select a valve based on the following critical parameters:
- Refrigerant type
- Evaporator size in tons, British Thermal Units per Hour (BTUH), or kW
- Evaporator temperature
- Liquid temperature at the QREV expansion valve inlet (the sub-cooling temperature)
- Pressure drop expected across the QREV valve
Use the following equation to calculate valve pressure drop:
ΔPValve = PCondenser – PEvaporator – PLoss
Sources of PLoss are:
- Pressure loss in evaporator lines and liquid lines
- Filter dryer pressure drop
- Solenoid valve pressure loss, if present
- Refrigerant distributor pressure drop
- Changes in elevation in liquid lines. This is usually not a factor in reach-in cases or display cases.
Use a factor of 0 if the parameters for the pressure drop in a line and filter are not known.
The following sections describe the QREV model selection process under AHRI/ANSI Standard 750-2007.