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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.
Outdoor heat exchanger heat transfer co-efficiency
Outdoor heat exchanger temperature (Tb)
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