Hitachi RAM-60QH4 Manuel De Service page 88

5. Reversing valve control circuit
Reversing valve
DC voltmater
or tester
※Since the reversing valve is differential pressure system, even when reversing valve is ON (collector voltage of Q831 is
about 0.8V normally), compressor rotation speed instructed by indoor microcomputer exceeds 3300min
⑤ microcomputer changes, and collector voltage of Q831 will be about 35V.
This does not indicate trouble. When rotation speed is reduced under 2700min
0.8V again. To measure voltage, connect ○ + terminal of tester to D831 anode and ○ - terminal to D line on the terminal
board.
• By reversing valve control circuit you can switch reversing valve ON / OFF (cooling ON) according to instruction from indoor
microcomputer and depending on operation condition.
Voltage at each point in each operation condition is approximately as shown below when measured by tester.
(When collector voltage of Q831 is measured)
Cooling
Heating
Dehumidifying
CN2
3
D831
1
Q831
V
0V
Operation condition
General operation of cooling
In normal heating operation
MAX. rotation speed instructed by indoor
microcomputer after defrost is completed
Defrosting
Sensor dry
35V
12V
PQ831
R833
R832
R831
Fig. 5-1
-1
Table 5-1
– 100 –
Micro
computer
24
IC8
-1
, signal at pin of
, collector voltage of Q831 will fall to about
Collector voltage of Q831
About 0.8V
About 35V
About 35V
About 0.8V
About 0.8V