Hitachi RAM-68NP3B, Service Manual, Page: 58 / 79

8. Hibernation Mode
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This model have designed to enter hibernation mode for energy saving and power consumption reduction during stanby.
1) Stanby continuesly
2) Unit in running condition, then off the unit by remote controller and leave the unit in stanby condition.
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During hibernation mode, DC voltage will be as below condition.
⑴
B-15V : Maintain at 15V
⑵
B-5V : Maintain at 5V
⑶
B-12V : Maintain at 12V
⑷
16V : Drop to 0V
⑸
12V : Drop to 0V
⑹
5V : Drop to 0V
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During hibernation activation, main microcomputer pin 49 will change to LOW condition.
Due to this pin become LOW, Q502, PQ102, and Q101 will be OFF. As Q101 OFF, 12V and 5V will drop to 0V.
Due to 5V drop to 0V, Q103 and Q102 will be OFF and causing 16V also drop to 0V.
Fig. 8-1
Main Microcomputer Standby output
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Unit will enter hibernation mode during below stanby condition if not received any signal from remote controller
and expansion valve already completed initialization .
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For inspection during hibernation mode, service person can measure DC voltage B-15V, B-12V and B-5V on
Main P.W.B.
But to measure DC voltage 16V, 12V and 5V on Inverter P.W.B., service person shall on the indoor unit by remote
controller first. This will change the unit from hibernation mode to normal.
All LED on the Main P.W.B and Inverter P.W.B (LD301, LD351, LD352, LD353, LD401, LD402 and LD403) will be OFF
during this mode.
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If outdoor unit have failure/error, all indication including error diagnosis LED will be OFF once the smoothing
capacitor (C019 ~ C021) voltage reduce to 29V.