SiBE04-101
General Functions
Main Function
21
1.4
Defrost Control
Principle
When frost deposit on the outdoor heat exchanger has increased in heating operation, change the
operation from heating cycle to cooling cycle for defrosting.
Start Conditions
Defrost control is set by the following conditions:
During heating
More than 35 minutes after the compressor has started up
When condition 1 or 2 in the table below are applicable:
Conditions
The following table shows the different conditions on which defrost control is based:
Condition
Description
1
More than 35 minutes of accumulated running time
Less than 90 minutes of accumulated running time
Condition 1, 2 or 3 in the table below
2
More than 90 minutes of accumulated running time
Condition 1, 4 or 5 in the table below
Conditions
Description
1
T
[outdoor heat exchanger]
< -12˚C for 1 min.
2
T
[ambient outdoor]
< 5˚C
T
[outdoor heat exchanger]
< (-5 + T
[ambient outdoor]
×
0.4)
check if T
[indoor heat exchanger]
decreases 5 times every 10 seconds
3
T
[ambient outdoor]
≥
5˚C
T
[outdoor heat exchanger]
< -3˚C
check if T
[indoor heat exchanger]
decreases 5 times every 10 seconds
4
T
[ambient outdoor]
<
5˚C for 60 seconds
T
[outdoor heat exchanger]
< (-5 + T
[ambient outdoor]
×
0.4) for 60 seconds
5
T
[ambient outdoor]
≥
5˚C for 60 seconds
T
[outdoor heat exchanger]
< -3˚C for 60 seconds
SiBE04-101.book Page 21 Monday, October 15, 2001 3:08 PM
