System control Si18-201
170 Main Functions
Monitoring
Function During
SkyAir Indoor
Unit Heating
Thermostat OFF
In the case of SkyAir indoor units, the fan operates at the L tap during heating thermostat OFF.
Therefore, the refrigerant continues to flow into the indoor heat exchanger. This can cause
condensation, causing liquid trap.
To prevent this, the BP unit sends a defrost signal (FD+FDS) to turn off the fan.
However, since the room temperature thermistor of the SA indoor unit is installed inside the
equipment, there is a possibility that the thermostat may not reset due to the continuous flow of
refrigerant during heating operation.
To solve this problem, the fan ON/OFF control is provided at predetermined intervals (ON time:
300 sec, OFF time: 90 sec) for indoor unit thermostat monitoring.
Abnormality
Processing
Icing prevention function for non-operating room units
When 10 minutes pass from the time a room unit stops operating while the compressor is in
operation, room temperature DAT and heat exchanger temperature DCT of the non-operating
room unit are detected.
DAT - DCT
≥
10 deg
DCT
≤
1°C
When conditions and remain for (5 minutes), an icing abnormality of the non-operating
room unit is determined.
The motorized valve of the abnormal room unit is opened to 2.3 Nm³/hr from the time an icing
abnormality is determined to the time the compressor stops.
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