Si30-408 Control of Indoor Unit
Basic Information 31
4.3 Freeze-up Prevention Control
Freeze-up prevention by off-cycle (The control be carried out with individual indoor unit.)
When the temperature detected by liquid pipe temperature thermistor (Th2) of the indoor heat
exchanger lowers, and the following ON condition is fulfilled, the unit enters freeze-up
prevention operation (forcedly thermostat off).
In freeze-up prevention operation, fan-tap is fixed at the flow rate of L. The operation will be
stopped with the OFF condition below.
ON condition: The temperature (Th2) is –1°C or less for cumulative 40 min., or –5°C or less for
cumulative 10 min.
OFF condition: The temperature (Th2) is +7°C or more for successive 10 min.
Conception of
Freeze-up
Prevention
Control
To make freezing uneasy
• Aiming to limit the frequency of thermostat on / off and keep comfortableness.
→
Wide range of continuous operation can be kept
• Aiming to maintain reliability of compressor
→
The frequency of compressor on/off is limited (Capacity control of indoor electronic
expansion valve).
To make sure to remove the frozen matter, once enter into frozen mode.
• Aiming to make sure to prevent water from leakage
→
The condition to remove the frozen matter completely is adopted.
Note: When multi-flow cassette (super cassette) of indoor unit is set as two-way or three-way
discharge, on condition is changed as below:
1°C or below continues for cumulative 15 minutes, or
0°C or below continues for continuous one minute
When freeze-up prevention is actuated, fan-tap is fixed at the flow rate of LL.
(Off condition is similar to the standard)
–5˚C
0˚C
+7˚C
Example: Case where temperature is –5˚C or less for cumulative 10 min.
For 10 min.
For 10 min.
Freeze-up prevention control
Forcedly thermostat OFF
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