04-09
4-5-4 Defrost operation control
3-8-3 DEFROSTING CONTROL
1) Purpose of operation
By removing the frost that was formed on the surface of the outdoor unit heat eachanger, the defrosting operation
prevents a decline in heat transfer efficiency and realizes an efficient heating operation.
2) About the defrosting operation
(a) Starting condition of the defrosting operation
The defrosting operation starts when all the following conditions are satisfied.
Outdoor unit operation mode is "heating".
Integrated time which any of the compressors is operating has reached 40 minutes or longer.
(b) End condition of the defrosting operation
When any of the following conditions is satisfied, defrosting operation ends.
The temperature of the heat exchanger in operation exceeds a certain temperature preset with DIP switch 6-3.
10 minutes or longer have elapsed since defrosting started.
When the operation mode is changed from heating to cooling.
The temperature of any outlet of heat exchanger in operation has become less than -10 C.
3) Others
During the defrosting operation the fans of indoor units stop,
appears on the display of wired and central
DEFROST
remote controller, and appears on the simple remote controller.
The operation indicators (LED) of the indoor units flash slowly.
(1) Starting condition of defrost operation
(2) Release condition of defrost operation
(3) Operation during defrosting
Accumulated heating time has passed 40min and 20min after oil recovery operation,
and then when it meets either of following conditions.
TH4(Heat Exchanger temperature sensor value) of all outdoor units defrost release temperature,
and passage of 20minutes and suction temperature of outdoor unit is lower than Judgment temperature
Accumulated heating time is reset to zero by "cooling operation" and "end of defrost operation".
If SW7-3(Setting up connecting capacity of indoor unit) is ON, the time is 90min.
temperature of starting defrost operation is calculated on the basis of
TH12(Outdoor temperature sensor value)
Defrost release temperature is calculated on the basis of TH12(Outdoor temperature sensor value).
( 5degC Defrost release temperature 12degC )
Condition 1) Accumulated time of TH4(Heat exchanger temperature sensor value) -2degC is over 195min.
Condition 2) Condition 2) Accumulated time of TH4(Heat exchanger temperature sensor value)
temperature of starting defrost operation is over 10min.
(Reference)
Outside air temperature = 5degC Temperature of starting defrost operation = - 8.0degC
Outside air temperature = 0degC Temperature of starting defrost operation = -11.5degC
Outside air temperature = -5degC Temperature of starting defrost operation = -19.0degC
(Indoor unit)
EEV : Open FAN : Stop
(Outdoor unit)
FAN : Stop Compressor : In operation
(it operates so that defrosting operation of master unit comes last.
Refer to following figure.)
[ STEP 1 ]
Master : Inverter compressor operates. Slave1 and Slave2 : All compressors operate.
[ STEP 2 ]
Master : All compressors operate. Slave1 and Slave2 : All compressors stop after defrost operation.
Master
Slave 1
Slave 2
Defrosting Defrosting Defrosting
Compressor
in operation
Stopped compressor
Master
Slave 1
Slave 2
Defrosting Defrosting end Defrosting end
Compressor
in operation
Stopped compressor
"Slave1 and Slave2 completed defrost operation" or
"STEP1 has passed 5min"
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