Mitsubishi Electric PUHZ-SW50VHA Service Manual page 18

9-1. REFRIGERANT COLLECTING (PUMP DOWN)
Perform the following procedures to collect the refrigerant when moving the indoor unit or the outdoor unit.
1 S upply power (circuit breaker).
• W hen power is supplied, make sure that "CENTRALLY CONTROLLED" is not displayed on the remote controller. If "CEN
TRALLY CONTROLLED" is displayed, the refrigerant collecting (pump down) cannot be completed normally.
• S tart-up of the indoor-outdoor communication takes about 3 minutes after the power (circuit breaker) is turned on. Start the
pump-down operation 3 to 4 minutes after the power (circuit breaker) is turned ON.
• I n the case of multi-units control, before powering on, disconnect the wiring between the master indoor unit and the slave
indoor unit. For more details refer to the installation manual for the indoor unit.
2 A fter the liquid stop valve is closed, set the SWP switch on the control board or switch board of the outdoor unit to ON. The
compressor (outdoor unit) and ventilators (indoor and outdoor units) start operating and refrigerant collecting operation begins.
LED1 and LED2 on the control board or switch board of the outdoor unit are lit.
• O nly set the SWP switch (push-button type) to ON if the unit is stopped. However, even if the unit is stopped and the SWP
switch is set to ON less than 3 minutes after the compressor stops, the refrigerant collecting operation cannot be performed.
Wait until compressor has been stopped for 3 minutes and then set the SWP switch to ON again.
3 B ecause the unit automatically stops in about 2 to 3 minutes when the refrigerant collecting operation is completed (LED1 off,
LED2 lit), be sure to quickly close the gas stop valve. If LED1 is lit and LED2 is off and the outdoor unit is stopped, refriger-
ant collection is not properly performed. Open the liquid stop valve completely, and then repeat step 2 after 3 minutes have
passed.
• I f the refrigerant collecting operation has been completed normally (LED1 off, LED2 lit), the unit will remain stopped until the
power supply is turned off.
4 T urn off the power supply (circuit breaker).
• N ote that when the extension piping is very long with large refrigerant amount, it may not be possible to perform a pump-
down operation. When performing the pump-down operation, make sure that the low pressure is lowered to near 0 MPa
(gauge).
Warning:
When pumping down the refrigerant, stop the compressor before disconnecting the refrigerant pipes. The compressor
may burst if air, etc. enters the system.
OCH525C
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