Mitsubishi Electric EHST20C-VM6HB Service Manual page 26

10-1. REFRIGERANT COLLECTING (PUMP DOWN)
When relocating or disposing of the indoor/outdoor unit, pump down the system following the procedure below so that no refriger-
ant is released into the atmosphere.
1 Turn off the power supply (circuit breaker).
2 Connect the low-pressure valve on the gauge manifold to the charge plug (lowpressure side) on the outdoor unit.
3 Close the liquid stop valve completely.
4 Supply power (circuit breaker).
• Even if power can be supplied, the pump down procedure cannot be completed depending on the unit's status. For more
information, refer to the FTC Installation Manual or Service Manual.
• Startup 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.
5 Perform the refrigerant collecting operation (cooling test run).
• Push the pump-down SWP switch (push-button type) on the control board of the outdoor unit. The compressor and ventilators
(indoor and outdoor units) start operating (refrigerant collecting operation begins). (LED1 and LED2 on the control board of
the outdoor unit are lit.)
• Only push the pump-down SWP switch if the unit is stopped. However, even if the unit is stopped and the pump-down SWP
switch is pushed less than 3 minutes after the compressor stops, the refrigerant collecting operation cannot be performed.
Wait until the compressor has been stopped for 3 minutes and then push the pump-down SWP switch again.
6 Fully close the ball valve on the gas pipe side of the outdoor unit when the pressure gauge on the gauge manifold shows 0.05
to 0 MPa [Gauge] (approx. 0.5 to 0 kgf/cm²) and quickly stop the air conditioner.
• Since the unit automatically stops in about 3 minutes when the refrigerant collecting operation is completed (LED1 off, LED2
lit), be sure to quickly close the gas ball valve. However, if LED1 is lit, LED2 is off, and the unit is stopped, open the liquid
stop valve completely, close the valve completely after 3 minutes or more have passed, and then repeat step 5. (Open the
gas ball valve completely.)
• If the refrigerant collecting operation has been completed normally (LED1 off, LED2 lit), the unit will remain stopped until the
power supply is turned off.
• Note that when the extension piping is very long with a large refrigerant amount, it may not be possible to perform a pump-
down operation. In this case, use refrigerant recovery equipment to collect all of the refrigerant in the system.
7 Turn off the power supply (circuit breaker), remove the gauge manifold, and then disconnect the refrigerant pipes.
Warning:
When pumping down the refrigerant, stop the compressor before disconnecting the refrigerant pipes.
• If the refrigerant pipes are disconnected while the compressor is operating and the stop valve (ball valve) is open, the
pressure in the refrigeration cycle could become extremely high if air is drawn in, causing the pipes to burst, personal
injury, etc.
10-2. UNIT REPLACEMENT OPERATION
When reusing the existing pipes that carried R22 refrigerant for the SW75/100/120 models, replacement operation
must be performed before performing a test run.
1 If new pipes are used, these procedures are not necessary.
2 If existing pipes that carried R22 refrigerant are used for the SW75/100/120 models, these procedures are not necessary.
(The replacement operation cannot be performed.)
3 During replacement operation, "C5" is displayed on "A-Control Service Tool (PAC-SK52ST)". (This is applied to only
SW75/100/120 models.)
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