Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 331

2) Control of fan for outdoor unit for de-icing
If DIP switch SW5-2 on the printed circuit board for the outdoor unit is set to on, the
fan on the outdoor unit which has been stopped will operate for 10 seconds at Hi speed
every 10 minutes when the outdoor air temperature is 3 °C or less.
3) Discharge temperature control during cooling/heating (Only case of FDC(P)208~508 type)
As the discharge gas temperature (detected with Th
bypass solenoid valve (SV1) are opened so that the abnormal rise of discharge gas temperature is prevented.
4) Defrost control
Defrost operation will start when the temperature of the heat exchanger for the outdoor unit (Tho-R detection) and the outdoor air
temperature (Tho-A detection) enter the start of defrost range shown in the figure below.
Initiation temp. of defrosting (Detected by Tho-R, Tho-A)
Note (1) If DIP switch SW5-1 on the printed circuit board for the outdoor unit is set to on, defrost operation will begin when temperature of the heat
exchanger for the outdoor unit reaches -7 °C.
a) Defrost Operation
Switching of the control of the 4-way selector valve during defrost operation can be performed by enabling/disabling the
jumper wire (J17) on the printed circuit board for the outdoor unit.
(i) J17 None (4-way selector valve ON during heater operation)
Defrost operation is performed with the compressor on, the fan for the outdoor unit off and the 4-way selector valve off.
(ii) J17 With (4-way selector valve OFF during heater operation)
Defrost operation is performed with the compressor on, the fan for the outdoor unit off and the 4-way selector valve on.
b) Defrost finished
(i) Once defrost operation has started, it will finish after the cumulative operating time of the compressor has reached 12
minutes (factory setting: SW5-1 OFF).
Note (1) This time will become 14 minutes if the DIP switch (SW5-1) on the printed circuit board on the outdoor unit is set to on.
(ii) Switching of the defrost recovery time can be performed by enabling/disabling the jumper wire (J18) on the printed
circuit board for the outdoor unit.
J18 (SW6-2) With: 14 °C, J18 (SW6-2) None: 18 °C
D) rises during cooling/heating operation, the capillary bypass and the liquid
O-
SV -open
SV -close
108 115
Discharge gas temp (°C)
-5
-10
-15
-20
(°C)
[Th -R]
0
-20 -15 -10 -5
Outdoor air temperature (°C) [Th
Outdoor fan
Zone for initiate temp. of defrost
0 5 10
-A]
0
FDT ( N ) -H
Outdoor fan
stopped
operates
at Hi speed
3 5
Outdoor air temperature (°C)
329