Mitsubishi Electric CITY MULTI PUHY-400YMF-C Service Handbook page 150

8) Compressor Replacement Procedure
When replacing a compressor, please proceed by the following procedure.
• When replacing the No. 1 compressor (variable capacity compressor), begin the replacement work after judging
whether the trouble is a compressor breakdown or an inverter breakdown. If only one of the compressors is defec-
tive, run the unit for about 1 hour in the emergency operation mode, checking the following items and judging if the
oil return circuit is defective or not before replacing the compressor.
• See the diagram at right concerning the temperature of each part.
<When Operating Normally>
1 Part A Temperature = Part C temperature; furthermore,
Part A temperature > ambient temperature + 20 deg.
2 Part B Temperature = Part C temperature; furthermore,
Part B temperature > ambient temperature + 20 deg.
<When Operating Abnormally>
If 1 is abnormal (outside the range),
Faulty oil return due to a faulty SV1 circuit (Replace the SV1 circuit).
If 2 is abnormal (outside the range),
Faulty oil return due to capillary being clogged (Replace the capillary).
(1) Make sure the main power supply is turned off.
If the reason why the compressor is being replaced is faulty insulation resistance, if the insulation resistance is 1 M
or greater, it is possible that it has dropped due to the dormancy of the refrigerant to the compressor, so after turning
on the power and heating for 12 hours or longer with a belt heater, turn off the power and check the insulation
resistance again.
(2) Remove the fin guard, front panel and front panel of the divider panel on the right side facing the front.
(3) Drain out the refrigerant from the high pressure and low pressure check joints.
(4) Oil will be spilt from the oil exhaust pipe when it is removed. Be careful please not to spill a large amount of oil.
Since oil absorbs moisture easily, do not leave the refrigerant circuit in the open state for long periods of time. Oil
which has been drained out cannot be reused.
(5) When the oil has stopped draining from the refrigerant and exhaust oil outlets, remove fastening fitting 1 loosen the
flare nuts on both ends of the oil equalization pipe and remove the oil equalization pipe.
(6) Close off the connection fittings for the oil equalization pipe of the compressors with simple caps, etc. to prevent oil
from leaking out.
(7) Remove the compressor terminal cover, then disconnect the power cable.
Caution: When replacing both compressors, please take measures to prevent faulty wire connections when the
compressors are reinstalled.
(8) Remove the discharge temperature thermistor and pipe fastening materials (a) ~ (e)*.
(9) Remove the belt heater.
(10) Heat up the soldered portions of the discharge piping, suction piping, volume control valve piping (All but model
PUHY-(P) 400YMF-C) and process piping (All but model PUHY-(P)400YMF-C) and disconnecting the piping.
(11) Remove the compressor mounting nuts and mounting fitting 2 (4 places on the No. 2 compressor only), then
remove the compressor.
Caution: When removing the compressor, be careful not to let oil from inside the compressor overflow from the
suction piping and process piping.
(12) Replace the compressor with a service unit.
PUHY-400·500YMF-C
PUHY-P400·500YMF-C
Caution: Do not mistake the replacement compressor.
(See 5 -[1] concerning the Emergency Operation Mode.)
Compressor
No. 1
400·500 400
HHV92FAA-YJ HH101YAA-J
HEV92FA1-YJ
HE101YAB-J
-147-
Four-way Valve
SV1 A
C
Oil
Accu-
Sepa-
B
mulator
rator
Capillary
No. 2
500
ZHC165YDA-J
ZEC165YAA-J
No. 1 Compressor
No. 2 Compressor