Mitsubishi Electric HP120TNU-A Service Handbook page 97

[4-1 Outdoor Unit Circuit Board Arrangement ]
(1) YNU
Fan board (left)
Capacitor board
INV board
DC reactor
(DCL)
*The figure above shows the unit seen from the
left after the front panel and the left side panel
were removed.
1) Refrigerant pipes are connected to the back of the control box. Do not forcibly pull out the control box. Doing so may result in
deformation of the pipe.
2) Exercise caution not to damage the front panel of the control box. Damage to this part affect the waterproof and dust proof
properties of the control box and may result in damage to its internal components.
3) A Faston terminal on the inrush current resistor has a locking function. Check that the terminal is securely locked in place.
Press the tab in the middle of the terminal to remove it.
4) Control box houses high temperature parts. Be well careful even after turning off the power source.
5) Perform the service after disconnecting the relay connector in the INV box (RYFAN1 and RYFAN2). Before plugging
in or unplugging connectors, check that the outdoor unit fan is not rotating and that the voltage across Pin 1 (+) and
Pin 5 (-) of connector RYPN in the INV box is 20 VDC or less. 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.
6) To connect wiring to TB7, check that the voltage is 20 VDC or below.
7) After servicing, reconnect the relay connector (RYFAN1 and RYFAN2) in the INV box as it was.
8) When opening or closing the front panel of the control box, do not touch any of the internal components. Before inspecting
inside the control box, turn off the power to the unit, leave it turned off for at least 10 minutes, and check that the voltage across
Pin 1 (+) and Pin 5 (-) of connector RYPN in the INV box is 20 VDC or less. It takes about 10 minutes to discharge electricity
after the power supply is turned off.
9) When the power is on, the compressor is energized even while it is stopped. Before turning on the power, disconnect all power
supply wires from the compressor terminal block, and measure the insulation resistance of the compressor. Check the com-
pressor for a ground fault. If the insulation resistance is 1.0 M or below, connect all power supply wires to the compressor
and turn on the power to the outdoor unit. It is energized to evaporate the liquid refrigerant that has accumulated in the com-
pressor.
2 -
chapter 4
Fan board (right) Noise filter
Cooling fan
RYFAN1, RYFAN2
In-rush current resistor
(R1, R5) Note 3)
Control board
Fuse holder
Power-supply terminal
block
Connector RYPN
(1 pin +, 5 pin -)
Transmission cable terminal
block (TB3, TB7)
PS board
back side
HWE18220_GB