Mitsubishi Electric PURY-P120Y(T)HMU-A, Service Handbook

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[
IX
Troubleshooting ]
- 275 - HWE0803A GB
-3- Solenoid Valve
Check whether the output signal from the control board and the operation of the solenoid valve match.
Setting the self-diagnosis switch (SW1) as shown in the figure below causes the ON signal of each relay to be output to the LED's.
Each LED shows whether the relays for the following parts are ON or OFF. LEDs light up when relays are on.
The circuits on some parts are closed when the relays are ON. Refer to the following instructions.
When a valve malfunctions, check if the wrong solenoid valve coil is not attached the lead wire of the coil is not disconnected, the
connector on the board is not inserted wrongly, or the wire for the connector is not disconnected.
(1) In case of 21S4a (4-way switching valve)
About this 4-way valve
When not powered:
Conducts electricity between the oil separator outlet and heat exchanger AND the gas ball valve (BV1) and the accumulator
to complete the circuit for the cooling cycle.
When powered:
The electricity runs between the oil separator and the gas ball valve, and between the heat exchanger and the accumulator.
This circulation is for heating.
Check the LED display and the intake and the discharge temperature for the 4-way valve to check whether the valve has no
faults and the electricity runs between where and where.Do not touch the pipe when checking the temperature, as the pipe
on the oil separator side will be hot.
Do not give an impact from outside, as the outer hull will be deformed leading to the malfunction of the inner valve.
(2) In case of SV1a (Bypass valve)
This solenoid valve opens when powered (Relay ON).
1) At compressor start-up, the SV1a turns on for 4 minutes, and the operation can be checked by the self-diagnosis LED display
and the closing sound.
2) To check whether the valve is open or closed, check the change of the SV1a downstream piping temperature while the valve
is being powered.Even when the valve is closed, high-temperature refrigerant flows inside the capillary next to the valve.
(Therefore, temperature of the downstream piping will not be low with the valve closed.)
(3) In case of SV2 (Bypass valve)
This solenoid valve opens when powered (Relay ON).
This valve turns on when low-pressure (LPS) drops to 0.25 MPa [36 psi] or below during Heating-only or Heating-main oper-
ation AND after 5 minutes have passed after compressor startup; OR when 63HS1 is above 3.5 MPa [507psi] with the SV9
turned on and SV5b turned off AND the frequency drops to the minimum.
To check whether the valve is open or closed, check the change of the SV1a downstream piping temperature while the valve
is being powered.Even when the valve is closed, high-temperature refrigerant flows inside the capillary next to the valve.
SW1
Display
LD1 LD2 LD3 LD4 LD5 LD6 LD7 LD8
Upper 21S4a CH11 SV1a SV2
Lower SV5b
Upper SV4a SV4b SV4c SV5c SV4d SV9
Lower
1 2 3 4 5 6 7 8 9 10
ON
SW1
1 2 3 4 5 6 7 8 9 10
ON
SW1