Refrigerant Leak - Mitsubishi Electric City Multi PQHY-P72 Service Handbook

[ IX Troubleshooting ]

[5] Refrigerant Leak

1. Leak spot: In the case of extension pipe for indoor unit (Cooling season)
1) Mount a pressure gauge on the service check joint (CJ2) on the low-pressure side.
2) Stop all the indoor units, and close the liquid ball valve (BV2) inside the heat source unit while the compressor is
being stopped.
3) Stop all the indoor units; turn on SW3-6 on the heat source unit main board while the compressor is being
stopped.(Pump down mode will start, and all the indoor units will run in cooling test run mode.)
4) In the pump down mode (SW3-6 is ON), all the indoor units will automatically stop when the low pressure (LPS)
reaches 0.382MPa [55psi] or less or 15 minutes have passed after the pump mode started. Stop all the indoor units
and compressors when the pressure indicated by the pressure gauge, which is on the check joint (CJ2) for low-
pressure service, reaches 0.284MPa [41psi] or 20 minutes pass after the pump down operation is started.
5) Close the gas ball valve (BV1) inside the heat source unit.
6) Collect the refrigerant that remains in the extended pipe for the indoor unit. Do not discharge refrigerant into the
atmosphere when it is collected.
7) Repair the leak.
8) After repairing the leak, vacuum the extension pipe and the indoor unit.
9) To adjust refrigerant amount and to check the composition of refrigerant, open the ball valves (BV1 and BV2) inside
the heat source unit and turn off SW3-6.
2. Leak spot: In the case of heat source unit (Cooling season)
1) Run all the indoor units in the cooling test run mode.
(i) To run the indoor unit in test run mode, turn SW3-2 from ON to OFF when SW3-1 on the heat source unit MAIN
board is ON.
(ii) Change the setting of the remote controller for all the indoor units to the cooling mode.
(iii) Check that all the indoor units are performing a cooling operation.
In case of PQHY series
2) Check the values of Tc and TH7.
(To display the values on the LED screen, use the self-diagnosis switch (SW1) on the heat source unit MAIN
board.)
(i) When Tc-TH7 is 10K [18°F] or more : See the next item 4).
(ii) When Tc-TH7 is less than 10K [18°F] : After the compressor stops, collect the refrigerant inside the system,
repair the leak, perform evacuation, and recharge new refrigerant. (Leak spot: In the case of heat source unit,
handle in the same way as heating season.)
Tc self-diagnosis switch
1 2 3 4 5 6 7
ON
In case of PQRY series
3) Check the values of SC16.
(To display the values on the LED screen, use the self-diagnosis switch (SW1) on the heat source unit MAIN
board.)
(i) When SC16 is 10K [18°F] or more : See the next item 4).
(ii) When SC16 is less than 10K [18°F] : After the compressor stops, collect the refrigerant inside the system, repair
the leak, perform evacuation, and recharge new refrigerant. (Leak spot: In the case of heat source unit, handle
in the same way as heating season.)
SC16 self-diagnosis switch
1 2 3 4 5
ON
4) Stop all the indoor units, and stop the compressor.
(i) To stop all the indoor units and the compressors, turn SW3-2 from ON to OFF when SW3-1 on the heat source
unit MAIN board is ON.
(ii) Check that all the indoor units are being stopped.
5) Close the ball valves (BV1 and BV2).
6) To prevent the liquid seal, extract small amount of refrigerant from the check joint of the liquid ball valve (BV2), as
the liquid seal may cause a malfunction of the unit.
7) Collect the refrigerant that remains inside the heat source unit. Do not discharge refrigerant into air into the atmo-
sphere when it is collected.
8) Repair the leak.
9) After repairing the leak, replace the dryer with the new one, and perform evacuation inside the heat source unit.
8 9 10
6 7 8 9 10
- 298 -
TH7 self-diagnosis switch
1 2 3 4 5 6 7 8 9 10
ON