Panasonic U-8ME2E8 Service Manual & Test Run Service Manual page 25

4. Special Control
4. Special Control
(8) SC Circuit Electronic Control Valve [MOV4]
8-1. Cooling SC Control
During cooling operation, the liquid refrigerant which condenses at the outdoor unit heat exchanger flows into
the receiver tank, and SC (sub-cool = super-cooling) approaches 0 degree.
When SC is small and the length of the tubing connecting the indoor and outdoor units is long, the refrigerant
flow in the indoor unit will be reduced significantly.
To prevent this trouble from occurring, MOV4 operates so as to increase super-cooling in the double tube coil.
MOV4 controls the difference of temperature between the SCG thermistor and low pressure saturated
temperature to 3 ~ 5 degrees Celsius.
8-2. Heating SC Control
For the type of 18HP and 20HP units, if the MOV1 or MOV2 opens more than 300 pulses, the MOV4 may
occasionally open between 100 and 350 pulses.
* The type of 8HP to 16HP units are not functioned.
8-3. Discharge Temperature Control of Compressor
When the discharge temperature increases
to 90°C or more, MOV4 opens to 100 pulses
to cool down the compressor.
Then, the MOV4 operates according to the state
of the discharge temperature between 20 ~ 480
pulses.
This operation takes priority over SC control.
This operation is continued until discharge
temperature decreases to 85°C or less.
(9) Crankcase Heater Control [CH1, CH2]
When the compressor stops, the crankcase heater of its own compressor is turned ON in the following conditions.
When the discharge temperature ≤ the outdoor air temperature + 15°C
When the outdoor air temperature ≤ 20°C
When the compressor stops and 30 minutes later.
Control Functions - Outdoor unit
Thermistor (SCG)
Liquid refrigerant
MOV4 (Discharge temperature control of compressor)
1 - 15
2WAY VRF SYSTEM
2WAY SYSTEM
Control Functions
Liquid refrigerant
returns to accumulator.
Does not fully evaporate,
resulting in liquid back-up.
Liquid refrigerant
1