Specifications

Special Control SiUS39-602
52 Function
3.3 Defrosting Operation
In order to melt the frost accumulated on the heat exchanger during heating operation,
Defrost operation is performed to restore the heating capacity.
[Starting conditions]
Start defrosting operation referring to the following conditions.
* Heat conductivity of outdoor heat exchangers
* Heat exchange temperature (Tb)
* Timer (Min. 2 hours)
The heat conductivity of outdoor heat exchangers is calculated based on Tc, Te, and
compressor load.
<Defrost starting condition>
Defrost operation is started when the outdoor heat exchanger temperature becomes lower than deicer temperature.
Defrost operation is conducted once in max. 2 hours.
Actuator
Defrost preparation
operation
Defrost operation Post-defrost operation
Compressor Upper limit control 143 Hz + ON
1 -st ep in c rea se fr om
(74Hz + OFF) to
(Pc - Pe > 0.4 MPa)
Outdoor unit fan
STEP7
or
STEP8
OFF STEP8
Four way valve 1
Depend on previous heat
exchange mode
OFF ON
Four way valve 2
Depend on previous heat
exchange mode
OFF OFF
Main motorized valve (EV1)
Four way valve 1
OFF:1400 pls
ON:SH control
1400 pls 180 pls
Sub motorized valve (EV2)
Four way valve 2
OFF:1400 pls
ON:SH control
1400 pls 1400 pls
Sub-cooling motorized valve (EV3) 0 pls 0 pls 0 pls
Hot gas bypass valve (SVP) OFF ON ON
Oil equalization valve (SVO) ON ON ON
Receiver gas charging valve (SVL) OFF OFF OFF
Receiver gas discharge valve (SVG) OFF OFF OFF
Discharging pipe stop valve (SVR) ON OFF OFF
Non-operating unit liquid pipe stop
valve (SVSL)
ON OFF OFF
High pressure gas pipe pressure
reduction valve (SVC)
OFF ON ON
Ending conditions 2 min.
• 12 min.
• Tb > 52°F
• 160 sec.
• Pc - Pe>58 psi
or
or
Indoor unit actuator During defrost
Fan
Cooling Thermostat ON unit Set Fan Speed
Heating Thermostat ON unit OFF
Stopping unit OFF
Cooling Thermostat OFF unit Set Fan Speed
Heating Thermostat OFF unit OFF
Electronic expansion valve
Thermostat ON unit 512 pls
Stopping unit 512 pls
Thermostat OFF unit 512 pls