Service Manual

Control Specification SiUS121502E
68 Function and Control
3.7 Freeze-up Protection Control
Outline During cooling operation, the signals sent from the indoor units control the operating frequency
limitation and prevent freezing of the indoor heat exchanger. (The signals from the indoor units are
divided into zones.)
Detail The operating frequency limitation is judged with the indoor heat exchanger temperature 2 seconds
after operation starts and 30 seconds after the number of operation room is changed.
3.8 Heating Peak-cut Control
Outline During heating operation, the indoor heat exchanger temperature determines the frequency upper
limit to prevent abnormal high pressure.
Detail

The operating frequency is judged with the indoor heat exchanger temperature 2 minutes after
the operation starts and
F
seconds after the number of operation room is changed.

The maximum value of the indoor heat exchanger temperature controls the following (excluding
stopped rooms).
(R17362)
Reset zone
Up zone
Keep zone
Dropping zone
Stop zone
13˚C (55.4˚F)
7˚C (44.6˚F)
3˚C (37.4˚F)
0˚C (32˚F)
5˚C (41˚F)
(Reference)
Indoor heat exchanger
thermistor temperature
A 65°C (149°F)
B 55°C (131°F)
C 54°C (129.2°F)
D 52°C (125.6°F)
E 50°C (122°F)
Zone Control
Stop zone When the temperature reaches the stop zone, the compressor stops.
Dropping zone The upper limit of frequency decreases.
Keep zone The upper limit of frequency is kept.
Up zone The upper limit of frequency increases.
Reset zone The upper limit of frequency is canceled.
Indoor heat exchanger
thermistor temperature
Stop zone
Dropping zone
Keep zone
Up zone
Reset zone
(R14665)
D
C
B
A
E
F (seconds)
30
2
When increase
When decrease