Defrosting - Mitsubishi Electric FDT125VNVF Technical Manual

(5)

Defrosting

(a) Defrosting start conditions
If all of the following defrosting conditions A or conditions
B are met, the defrosting operation starts.
1) Defrosting conditions A
a) Cumulative compressor operation time after the
end of defrosting has elapsed 37 minutes, and the
cumulative compressor operation time after the
start of heating operation (remote controller ON)
has elapsed 30 minutes.
b) After 5 minutes from the compressor ON
c) After 5 minutes from the start of outdoor unit fan
d) After satisfying all above conditions, if temperatures
of the outdoor unit heat exchanger temperature
thermistor (Tho-R1, R2) and the outdoor air
temperature thermistor (Tho-A) become lower
than the defrosting start temperature as shown
by the right figure for 15 seconds continuously,
or the suction gas saturation temperature (SST)
and the outdoor air temperature (Tho-A), which
are obtained from the value detected by the
low pressure sensor (LPT) stay for 3 minutes
within the range below the defrosting operation
start temperature as shown by the right figure.
However, it excludes for 10 minutes after the start
of compressor and the outdoor air temperature is
as shown by the lower figure.
LPT detection
2) Defrosting conditions B
a) When previous defrosting end condition is the time out of defrosting operation and it is in the heating operation
after the cumulative compressor operation time after the end of defrosting has become 30 minutes.
b) After 5 minutes from the start of compressor
c) After 5 minutes from the start of outdoor unit fan
(b) Defrosting end conditions
When any of the following conditions is satisfied, the defrosting end operation starts.
1) When it has elapsed 8 minutes and 20 seconds after the start of defrosting. (After 10 minutes and 20 seconds for
model, 200 and 250)
2) When the outdoor unit heat exchanger temperatures (Tho-R1, R2), whichever the lower, becomes 12°C or higher for
10 seconds continuously.
(c) Switching of defrosting control with SW3-1
1) If SW3-1 on the outdoor unit control PCB is turned to ON, it becomes easier to enter the defrosting operation. Use
this when installing a unit at snowing regions.
2) Control contents
a) It allows entering the defrosting operation under the defrosting condition A when the cumulative heating
operation time becomes 30 minutes. It is 37 minutes at SW3-1 OFF (Factory default).
b) It allows entering the defrosting operation under the defrosting condition B when the cumulative heating
operation time becomes 25 minutes. It is 30 minutes at SW3-1 OFF (Factory default).
c) It allows the defrosting operation with the outdoor unit heat exchanger temperature (Tho-R) and suction
pressure saturation temperature (SST) being higher than normal.
LPT invalid
2 4
Outdoor air temp. (°C)
-
-25
-27
-30
-25 -20 -18
Model 71 ~ 250
-2
Model 71
-8 -5
-6
-10
-10
-15
-15
-20
-24
-20
-25
-30
-31
-25
-27
-35
-25 -20 -18
-30
-25 -20
-18
Model 100 ~ 250
Model 71
-8
-8
-10
-10
-15
-15
-20 -20
-24
-24
-25
-25
-30
-28.6
-31
-30
-18
-25 -20
-35
-25 -20 -18
Model 100 ~ 250
-8
-10
-15
-20
-24
-25
-28.6
-30
-25 -20 -18
321
-
'12 • PAC-T-174
-15 -10 -5 0
Outdoor air temp. (℃)［Tho-A］
Defrost operation start
temperature zone
Defrost operation start
temperature zone
-15 -10 -5 0
Outdoor air temp. (℃)［Tho-A］
-15 -10 -5 0
Outdoor air temp. (℃)［Tho-A］
Defrost operation start
temperature zone
Defrost operation start
temperature zone
-15 -10 -5 0
Outdoor air temp. (℃)［Tho-A］
-15 -10 -5 0
Outdoor air temp. (℃)［Tho-A］
Defrost operation start
temperature zone
-15 -10 -5 0
Outdoor air temp. (℃)［Tho-A］
5 6 10
5 6 10
5 6 10
5 6 10
5 6 10
5 6 10