SiBE18-821_C Special Control
Function 85
3.3 Defrosting Operation
The defrosting operation is performed to solve frost on the outdoor unit heat exchanger when
heating, and the heating capacity is recovered.
[Conditions to start]
The defrosting operation is started referring following conditions.
îš„
Outdoor heat exchanger heat transfer co-efficiency
îš„
Outdoor heat exchanger temperature (Tb)
îš„
Timer (2 hours at the minimum)
In addition, outdoor heat-exchange co-efficiency is derived from Tc, Te, and the compressor
load.
* From the preparation to the defrost operation, and from the defrost operation to the post
defrost operation, the compressor stops for 1 minute to reduce noise on changing of the four
way valve.
Outdoor unit actuator
Defrost preparation
operation
Defrost operation Post defrost operation
Compressor Upper limit control 140 Hz Full load
2-step increase from
36 Hz Unload to (Pc –
Pe > 0.4 MPa) every
20 sec.
Outdoor fan STEP 8 OFF STEP 8
Four way valve (Y1S) ON OFF ON
Main electronic expansion valve
(Y1E)
SH control 480 pls 55 pls
Subcooling electronic expansion
valve (Y3E)
0 pls 0 pls 0 pls
Hot gas bypass valve (Y2S) OFF ON ON
Ending conditions 2 min.
• 15 min.
• Tb > 11°C
• Ts1 – Te < 5°C
• 160 sec.
• Pc – Pe > 0.4 MPa
or
&
{
or
Indoor unit actuator Operation
Indoor fan
Thermostat ON unit OFF
Stopping unit OFF
Thermostat OFF unit OFF
Electronic expansion valve of
BP unit
Thermostat ON unit SH control
Stopping unit 80 pls
Thermostat OFF unit SH control
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