Description Of Main Circuit Operation - Hitachi RAC-18SX8 Service Manual

DESCRIPTION OF MAIN CIRCUIT OPERATION

MODEL RAS-18SX8
1. Power relay operation
Power
Power relay
ON signal
(from pin 60 of
microcomputer)
Operation sequence of relay
・When the product becomes operable in response to remote control or other operation, the power
relay is turned on to power the outdoor unit.
・When dirt or mold monitoring is configured or when it is less than 2 hours until the ON timer count is
up, the power relay is turned on.
・6 minutes after there are no more turn-on factors, the power relay is turned off.
・If the self-diagnosis function of the indoor and outdoor units detects failure mode, the power relay is
turned off.
Check
If the terminal board is overheated due to a poorly inserted cable in the indoor terminal board, resulting in
the terminal board temperature fuse becoming melted down, the power to the operation coil of the power
relay is shut down and the relay is turned off to stop the power supply to the indoor unit. At the same time,
the power supply to the indoor/outdoor communication circuit will be shut down, resulting in the
communication function being stopped. (In that case, the failure display will consist of the timer lamp
blinking 3 times.)
Indoor electrical installation
Power relay
Control
power
circuit
Operation command of
remote controller
Power relay
A
B
12V
Terminal board
Temperature fuse
C
Indoor/outdoor
communication circuit
0.7 second
Fig. 1-1
– 158 –
Outdoor electrical installation
A
Smoothing
capacitor
B
C
Indoor/outdoor
communication circuit