Special Control SiUS371614E83 Functions and Control7.3 Defrost OperationTo defrost the outdoor heat exchanger while in Evaporator, the defrost operation is conducted to recover the heatingcapacity.Tb: Heat exchanger deicer temperaturePart Name Electric Symbol Defrost operationREYQ72TA REYQ96-168TAInverter compressor 1 M1C M1C REYQ72TA: 282 HzREYQ96-168TA: 252 Hz + 252 HzInverter compressor 2 — M2C With high pressureOFF ←→Step X/2 ←→ Step XInverter fan M1F M1F, M2FElectronic expansion valve (Heatexchanger upper) Y1E Y1E100%Electronic expansion valve (Heatexchanger lower) Y3E Y3EElectronic expansion valve(Subcooling heat exchanger) Y2E Y2E 0 pulseElectronic expansion valve(Receiver gas purge) Y4E Y4E 0 pulseElectronic expansion valve(Inverter cooling) Y5E Y5E Same as normal operationSolenoid valve (Oil separator oilreturn) Y1S Y1S, Y2S ONSolenoid valve (Liquid pipe) Y3S Y3S ONFour way valve (HP/LP gas pipe) Y4S Y4S HoldFour way valve (Heat exchangerlower) Y5S Y5S HoldFour way valve (Heat exchangerupper) Y6S Y6S HoldEnding condition • A lapse of 15 minutes• Tb>11°C (51.8°F) continues for 30 seconds or moreORIndoor unit actuator Defrost operationFanThermostat ON unit OFFStopping unit OFFThermostat OFF unit OFFElectronic expansionvalveThermostat ON unit Defrost EV opening degreeStopping unit Defrost EV opening degreeThermostat OFF unit Defrost EV opening degreeBranch selector unit actuator Normal cooling Normal Simultaneous Cooling / Heating Normal heatingCooling Cooling Heating HeatingElectronicexpansionvalve (EVSC) Y1EThermostat ON 0 pulse 0 pulse Subcooled degreecontrol 0 pulseStopping 0 pulse 0 pulse 0 pulse 0 pulseThermostat OFF 0 pulse 0 pulse 0 pulse 0 pulseElectronicexpansionvalve (EVH) Y2EThermostat ON 6,000 pulse 0 pulse 6,000 pulse 6,000 pulseStopping 6,000 pulse 0 pulse 6,000 pulse 6,000 pulseThermostat OFF 6,000 pulse 0 pulse 6,000 pulse 6,000 pulseElectronicexpansionvalve (EVL) Y3EThermostat ON 6,000 pulse 6,000 pulse 0 pulse 0 pulseStopping 6,000 pulse 6,000 pulse 0 pulse 0 pulseThermostat OFF 6,000 pulse 6,000 pulse 0 pulse 0 pulse
