Brochure

Parker Hannifin Corporation
Climate & Industrial Controls Group
Cleveland, OH
Catalog CIC-2003-1/US
Thermostatic and Constant Pressure (Automatic) Expansion Valves
182
Thermal Electric ValvesApplications
Improving the Operating Performance and Cost of
Heat Pumps
Bi-directional operation makes the electric valve a
popular heat pump control. One electric valve and one
or two thermistors reduce the number of components
normally used: two thermostatic types, two check
valves and their connections.
• Application A: The first heat pump uses only one
thermistor in the common suction line between the
reversing valve and the compressor. This produces a
saturated vapor entering the compressor.
• Application B: Two thermistors, wired in series with
the electric valve, are used in the second schematic.
With this arrangement, suction gas entering the
compressor is slightly superheated due to heat
transfer in the reversing valve.
1. During cooling, thermistor #2 controls the electric
valve. Thermistor #1 is in the compressor dis-
charge line. Thermistor #1 has no effect on valve
operation because it is sensing hot gas and self-
heating to low resistance (full open).
2. In the heating cycle, thermistor #1 controls the
valve and thermistor #2 is located in the compres-
sor discharge line. Compressor protection during
defrost cycles is another advantage of the
system.
Thermal Electric Valve Model 625 — Applications
Parker's thermal electric valve can be used for a variety of applications demanding control functions that are diffi-
cult to accomplish with thermostatic expansion valves. When considering this valve for an application, consider
that the thermal electric valve inherently provides the following benefits:
Eliminating Super Heat in Evaporators
The thermal electric valve maintains zero degrees su-
perheat in the evaporator at all loads. This means that
10-15% more evaporator coil surface is available for
added cooling capacity.
• Approximately 10 percent additional coil capacity.
• Rapid system unloading.
• Controlled suction refrigerant quality or superheat.
• Cool suction gas.
• Similar capacity stroke from – 20°F (-29°C) through
+ 40°F (+4°C).
• Reduction in valve inventory (no special bulb
charges, no external equalizers, no superheat
settings).
Compressor
625 Electric Valve
Indoor
Coil
Outdoor
Coil
Bleed
Tube
4 Way
Valve
Thermistor
Accumulator
Heating
Cooling
(A)
cooling
cooling
heating
heating
(B)
Compressor
Thermistor 2
625 Electric Valve
Outdoor
Coil
Indoor
Coil
Bleed
Tube
4 Way
Valve
Accumulator
24 Volts Line
Thermistor 1
Heating
Cooling
cooling
cooling
heating
heating
Optional Bleed
Connection
625 Electric
Valve
Evaporator Coil
Compressor
Condensor Coil
Receiver
24 Volts Line