Mitsubishi Heavy Industries FDTCVA SERIES Technical Manual page 179

(f) Defrosting
(i ) Defrosting start conditions
If all the following defrosting conditions A or B are
satisfi ed, defrosting operation starts.
1) Defrosting conditions A
a) When cumulative operating time of the
compressor elapses 45 minutes or more
after the previous defrosting operation ends,
or 30 minutes or more after the heating
operation starts (with pressing RUN button
on the remote controller).
b) 5 minutes passes after the compressor goes
ON.
c) 5 minutes passes after the outdoor unit fan
runs.
d) When either of the following condition is
established;
1) When the relation between the outdoor
heat exchanger temperature (Tho-R1 or
R2, whichever lower) and ambient air
temperature (Tho-A) is in the defrost-
ing operation start temperature zone for
continuous 15 seconds, or.
2) When the relation between the suction gas
suturated temperature (SST) and ambient
air temperature (Tho-A) is in the zone for
3 minutes. However, under the following
condition this judgment is not done.
a) Less than 10 minutes have passed since
the compressor starts.
PSL Detecting
Ambient air temperature (˚C)
2) Defrosting conditions B
a) When cumulative operating time of the compressor elapses 30 minutes in case the previous defrosting operation
is fi nished with the condition 1), defrosting operation time being up.
b) 5 minutes have passed since the compressor started.
c) 5 minutes have passed since the outdoor unit's fan started running.
(ii) Changing the defrosting start temperature
When the DIP switch (SW3-1) on the outdoor unit control PCB is turned on, the following condition is changed.
1) When cumulative operating time of the compressor elapses 30 minutes or more instead of 45 minutes after the
previous defrosting operation ends.
2) When cumulative operating time of the compressor elapses 25 minutes instead of 30 minutes in case the previous
defrosting operation is fi nished with the condition 1), defrosting operation time being up.
3) Defrosting operation starting zone is changed as shown on the graph on the previous page.
4) Besides items 1), 2), and 3), other conditions are the same as the standard conditions.
PSL Disabled
2 4
178
-
Model FDCVA 302~1002
-2
-5
-10
-15
-17
-20
-21
-23
-25
-23 -20 -15
Ambient air temperature (˚C) [Tho-A]
Model FDCVA 302
-8
-10
-15
-20
-24
-25
-30
-31
-35
-25 -20 -18 -15
Ambient air temperature (˚C) [Tho-A]
Models FDCVA 402~1002
-8
-10
-15
-20
-24
-25
-30
-23 -20 -15
Ambient air temperature (˚C) [Tho-A]
-
Defrosting operation start
temperature zone
-10 -5 0 5 6
Defrosting operation start
temperature zone
-10 -5 0 5 6
Defrosting operation start
temperature zone
-10 -5 0 5 6
10
10
10