Test Run; Before Test Run - Mitsubishi Electric PAAA18AA1 Installation Manual

16. Test run

16.1. Before test run

After completing installation and the wiring and piping of the indoor and outdoor units, check for refrigerant
leakage, looseness in the power supply or control wiring, wrong polarity, and no disconnection of one
phase in the supply. Use a 500-volt megohmmeter to check that the resistance between the power supply
terminals and ground is at least 1.0 MΩ. Do not carry out this test on the control wiring (low voltage circuit)
terminals.
CAUTION
If set to SW01-2 ON in relay board , the furnace will start heating immediately upon a loss
of power to the outdoor unit. To avoid this, be sure to power up the outdoor unit prior
to powering up the furnace. Conversely, when powering down the system, the furnace
should be powered down prior to powering down the outdoor unit. Refer to "DIP switch for
emergency thermostat" section for detailed switch specifications.
WARNING
Do not use the air conditioner if the insulation resistance is less than 1.0 MΩ. Otherwise,
results such as electric shock, fire or explosion may occur.
Open the lock valves isolating the PAA unit from the outdoor unit before starting operation
to avoid refrigerant pipe bursting during furnace operation.
After installation or after the power source to the unit has been cut for an extended period, the insulation re-
sistance will drop below 1 MΩ due to refrigerant accumulating in the compressor. This is not a malfunction.
Perform the following procedures.
1. Remove the wires from the compressor and measure the insulation resistance of the compressor.
2. If the insulation resistance is below 1 MΩ, the compressor is faulty or the resistance dropped due the
accumulation of refrigerant in the compressor.
3. After connecting the wires to the compressor, the compressor will start to warm up after power is
supplied. After supplying power for the times indicated below, measure the insulation resistance again.
• The insulation resistance drops due to accumulation of refrigerant in the compressor. The resistance
will rise above 1 MΩ after the compressor is warmed up for two to three hours. (The time necessary to
warm up the compressor varies according to atmospheric conditions and refrigerant accumulation.)
• To operate the compressor with refrigerant accumulated in the compressor, the compressor must be
warmed up at least 12 hours to prevent breakdown.
4. If the insulation resistance rises above 1 MΩ, the compressor is not faulty.
© 2022 Mitsubishi Electric US, Inc.
PAA-A18, 24, 30, 36, 42AA1/BA1/CA1
98 Specifications are subject to change without notice.