Precautions For Servicing - Mitsubishi Electric PQHY-P72ZLMU-A Service Handbook

[ I Read Before Servicing ]

[13] Precautions for servicing

Control boxes house high-voltage and high-temperature electrical parts.
They may still remain energized or hot after the power is turned off.
When opening or closing the front cover of the control box, keep out of contact with the internal parts.
Before inspecting the inside of the control box, turn off the power, leave the unit turned off for at least 10 minutes, and check
that the voltage of the electrolytic capacitor (inverter main circuit) has dropped to 20 VDC or less.
When the unit is turned on, the compressor will remain energized even when it is stopped to vaporize the liquid refrigerant
that accumulates in the compressor.
When replacing the internal electrical components of the control box, tighten the screws to the recommended tightening
torque as specified below.
Recommended tightening torque for the internal electrical components of the control box
Screw Recommended tightening torque (N·m)
M3
M3.5
M4
M5
M6
M8
*1 When replacing the inverter board, apply heatsink grease to the semiconductor module on the back of the inverter board
evenly, pretighten the screws to hold semiconductor module to one-third of the specified torque, and then tighten the
screws to the specified torque.
*2 Deviating from the recommended tightening torque may cause damage to the unit or its parts.
Take the following steps to ensure that the screws are properly tightened.
1) Ensure that the spring washers are parallel to the terminal block.
Even if the tightening torque is observed, if the washers are not parallel to the terminal block, then the semiconductor module
is not installed properly.
Loose screws
2) Check the wires are securely fastened to the screw terminals.
Screw the screws straight down so as not to damage the screw threads.
Hold the two round terminals back to back to ensure that the screw will screw down straight.
After tightening the screw, mark a line through the screw head, washer, and terminals with a permanent marker.
Example
Mark a line.
Poor contact caused by loose screws may result in overheating and fire.
Continued use of the damaged circuit board may cause overheating and fire.
HWE15150
0.69
0.95
1.47
2.55
2.75
6.20
Proper installation
Daisy-chain (transmission line only)
Power wires,transmission lines
Place the round terminals back to back.
Terminal blocks (TB1,TB3,TB7)
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Spring washers are parallel to
the terminal block
GB