Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 138

SCM-HG (4 room)
(f) Defrosting
(i) When the following conditions are met, the defrosting operation will start.
1) During normal operation
a) When 30 minutes has passed since the start of heating or 30 minutes after the last defrosting (Cumulative actual
operating time of compressor at outdoor unit frequency of 16 Hz or more).
When the outdoor heat exchanger thermistor temperature is -3 °C or less for 3 continuous minutes after 27 minutes
b)
have passed.
c) Outdoor thermistor temperature – Outdoor gas piping thermistor temperature
ture + 5 °C or more.
d) When the compressor is operating.
u In addition, defrosting operation will start when the count of the decision frequency has become 0 Hz reaches 10
times or more and when all the conditions presented above in a), b) and d) are met.
2) During defrosting acceleration
a) When 30 minutes has passed since the last defrosting (Cumulative actual operating time of compressor at outdoor
unit frequency of 16 Hz or more).
b) When the compressor is operating.
u In addition, defrosting operation will start when the count of the decision frequency has become 0 Hz reaches 10
times or more and when all the conditions presented above in a) and b) are met.
Note (1) Defrosting acceleration is when the finishing of the previous defrosting is according to the defrosting conditions of the 10 minutes that have
passed.
3) Operation of function component in defrosting
Outdoor unit frequency
Solenoid valve (SVDf)
Outdoor unit fan
4-Way valve
Solenoid valve
(SVA, B, C, D)
[Operating units]
Solenoid valve
(SVA, B, C, D)
[Stopped units]
Electronic Expansion valve
(EVA, B, C, D)
[Operating units]
Electronic Expansion valve
(EVA, B, C, D)
[Stopped units]
4) Conditions for finishing defrosting
When any of the following conditions is met, the defrosting finishing operation will start.
1 When the temperature of the heat exchanger thermistor is 8 °C or more.
2 When 10 minutes has passed after the start of defrosting.
136
Decision frequency
90Hz
70Hz
50Hz
28Hz
ON
OFF
According to outdoor unit frequency
LO
OFF
ON
OFF
ON
OFF
ON
OFF
According to outdoor unit frequency
According to 28Hz
75 Pulses
Starting defrosting operation
Starting defrosting operation
≤
200 pulses
150
seconds Defrosting operation
Finishing defrosting operation
0.44 × Outdoor thermistor tempera-
Note (1) Indoor unit fan is
in response to Hot
Keep.
28Hz
Finishing defrosting operation 120 seconds