254
FDTN-H
-20
-20
-15
-10
-5
-15 -10 -5
Outdoor air temperature (°C) [Th
0
-A]
Heat exchanger temperature
(°C)
[Th
0
-R]
0510
Zone for initiate temp. of defrost
Initiation temp. of defrosting
3) 4-way valve control (1 phase models only)
In order to maintain the pressure balance after the stop of compressor during cooling, dehumidifying and heating operation.
the 4-way valve is controlled repeatedly as illustrated below.
4-way valve
(During cooling)
(During heating)
Compressor (During cooling, heating)
ON
OFF
ON
OFF
ON
OFF
120 sec.
50 sec.
171 sec. or over
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
5)
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)
SV -close
SV -open
Discharge gas temp.
115°C118°C
4) Discharge temperature control during cooling/heating
As the discharge gas temperature (detected with ThO-D) rises during cooling/heating operation, the capillary bypass and the
liquid bypass solenoid valve (SV1) are opened so that the abnormal rise of discharge gas temperature is prevented.
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