Checking Operation of Expansion Valve
Checking Operation Of Expansion Valve (EEV)
To check if the expansion valve is closing properly:
Install a pressure
After the system
The Expansion valve position can be monitored from the LED display pressing the “MONITOR” button and scrolling to ESP. This will indicate the number of steps the valve is open.
This can also be checked by using the EXV test pins on the board. This is indicated by a 0 to 5 Volts DC signal. At 0 Volt the valve is closed and at 5 Volts the valve is fully open. At values between 0 and 5 Volt, the valve will be opened proportionately.
Use the “MONITOR” button to display “SCP”” Evaporator Suction Pressure. Record the pressure displayed. Start the system and observe the pressure displayed. If the pressure does not increase, the expansion valve could be defective.
If the system is running, use the “MONITOR” button to display “SCP” Evaporator Suction Pressure. Record the pressure displayed. While the system is running, press the “FORCE SERVICE” button. Observe the pressure while the system is pumping down. The pressure should decrease. If it does not, this indicates a defective valve.
Expansion Valve Motor Winding Resistance
If the expansion valve is suspected of not functioning properly the motor windings resistance should be measured. This is a bipolar motor with two windings. Measure the resistance at the pins, on top of the valve, between locations A and B
or C and D.
(Note that the pins are not labeled A, B, C, D. This labeling is just for reference. Also, two of the pins, at location B and location D, have a wider spacing between them than between location A and C)
Expansion Valve
A• •C
••
B D
Motor Winding
Pins
For valve size 29320003 and 2930004, the resistance measured between pin locations A and B or C and D should be approximately 336 Ohms when valve is at 75ºF.
For valve size 2930007, 29320008, 29320013 and 29320014, the resistance measured between pin locations A and B or C and D should be approximately 116 Ohms when the valve is at 75ºF.
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