Precautions For Wiring - Mitsubishi Electric R410A Service Handbook

[1-4 Precautions for Wiring ]

1-4

Precautions for Wiring

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.
It will take approximately 10 minutes until the voltage is discharged after power off.
Perform the service after disconnecting the fan board connector (CNINV) and the inverter board connector (CN1 or
CNFAN). To plug or unplugconnectors, check that the outdoor unit fan is not rotating and that the voltage of capac-
itor in the main circuit is 20 VDC or below. The capacitor may collect a charge and cause an electric shock when the
outdoor unit fan rotates in windy conditions. Refer to the wiring nameplate for details.
If the outdoor unit fan is rotated by external forces such as strong winds, the main circuit capacitor can be charged and cause
an electric shock.
Refer to the wiring nameplate for details.
Reconnect the connector (CNINV) back to the fan board and reconnect the connector (CN1 or CNFAN) back to the inverter
board after servicing.
When the power is on, the compressor or heater is energized even while the compressor is stopped.
It is energized to evaporate the liquid refrigerant that has accumulated in the compressor.
Before connecting wiring to TB7, check that the voltage has dropped below 20 VDC.
When a system controller is connected to the centralized control transmission cable to which power is supplied from the out-
door unit (power jumper on the outdoor unit is connected to CN40), be aware that power can be supplied to the centralized
control transmission and the system controller may detect an error and send an error notice if the outdoor unit fan is rotated
by external forces, such as strong winds, even when power to the outdoor unit is turned off.
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
M4
M5
M6
M8
1 When replacing semiconductor modules (e.g., diode stack, IPM, INV board (with IPM), fan board (with IPM)), apply heat-
sink silicone evenly to the mounting surface of the semiconductor module (or the semiconductor module on the back of
the circuit board). Next, tighten the screws holding the 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
HWE14080
0.69
1.47
2.55
2.75
6.20
Proper installation
- 13 -
Spring washers are parallel to
the terminal block
GB