Panasonic U-10MF1E8 Service Manual page 26

7. Outdoor Unit Electronic Control Valves
[MOV1, MOV2, MOV3, MOV4]
7-4. SC Circuit Electronic Control Valve [MOV4]
(1) Operation to increase SC
During cooling operation, or mixed heating/cooling operation when the outdoor unit heat exchanger is
functioning as a condenser, the liquid refrigerant which condenses at the outdoor unit heat exchanger flows into
the receiver tank, and SC (sub-cool = supercooling) approaches 0°C. When SC is small and the length of the
tubing connecting the indoor and outdoor units is long, the pressure loss increases, possibly resulting in lower
capacities. Therefore, MOV4 operates at the double tube near the discharge port of the outdoor unit in order to
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increase SC.
MOV4 uses the receiver tank detection sensor and low-pressure sensor located near the accumulator to
perform control in order to prevent liquid back-up.
(2) Operation when discharge temperature is high
When the discharge temperature increases, the SC circuit electronic control valve opens to 480 pulses. This
intentionally causes a mild liquid back-up, cooling the compressor. This operation takes priority over operation
intended to increase SC. It is performed at top priority in all operating modes.
Gas refrigerant returns
to the accumulator.
Liquid refrigerant
(large SC)
Liquid refrigerant returns
to the accumulator.
Liquid refrigerant
Refrigerant on the outer side evaporates,
cooling the liquid refrigerant on the inner side.
Electronic control valve 4
(expansion valve) controls the fl ow.
Does not fully evaporate,
resulting in liquid back-up.
Electronic control valve
4 opens to 480 pulses.
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3-WAY SYSTEM
Control Functions
Liquid refrigerant (SC = 0°)
Liquid refrigerant