Mitsubishi MT300 User Manual

'10 • HM-T-149A
47
Defrosting
1) Defrosting start conditions
If all of the following defrosting condition A or condition B are met, the
defrosting operation starts.
For model 140, SV1 is open when 4 way valve switches, and closed when
low pressure keeps 0.55MPa or higher for 5 seconds or longer.
a) Defrosting conditions A
i) Cumulative compressor operation time after the end of defrosting
has elapsed 37 [45] minutes (15 minutes in case the previous defrost
operation is forcibly finished by indoor unit protection control)
and the cumulative compressor operation time after the start of
heating operation has elapsed 30 minutes
ii) After 5 minutes from the compressor ON.
iii) After 5 minutes from the start of outdoor fan.
iv) After satisfying all above conditions, if the outdoor heat exchanger
temperature (Tho-R1, Tho-R2, whichever the lower) and the
outdoor air temperature (Tho-A) become lower than the defrosting
start temperature as shown in Fig 4-1 for 15 seconds continuously.
Or suction gas saturated temperature (SST), which is detected by
the low pressure sensor (LPT), and the outdoor air temperature
(Tho-A) stay for 3 minutes within the temperature range lower
than the defrosting operation start temperature as shown Fig 4-2.
However it is not effective during 10 minutes after the start of
compressor and if the outdoor air temperature is within the range
of LPT invalid as shown in below gure.
2
4
LPT invalid
LPT detecting
Outdoor air temperature (°C)
Note: Figure in [ ] is for model 71.
b) Defrosting conditions B
i) If the previous defrosting was ended compulsorily due to the time out of defrosting operation period and
cumulative compressor operation time after the end of defrosting has elapsed 30 minutes and operation mode is
kept heating.
ii) After 5 minutes from the compressor ON.
iii) After 5 minutes from the start of outdoor fan.
2) Defrosting end conditions
When any of following conditions is satised, the defrosting operation is ended.
a) When it has elapsed 8 minutes and 20 seconds after the start of defrosting. (After 10 minutes and 20 seconds for
model 71)
b) When the outdoor heat exchanger temperatures (Tho-R1, Tho-R2) , whichever the lower, becomes 12°C or higher
continuously for 10 seconds.
3) Switching of defrosting control with SW3-1
a) If the dip switch SW3-1 on the outdoor control PCB is turned ON, it makes earlier to enter the defrosting operation.
Use this function, if installing the unit in snowing region.
b) Control contents
i) It allows entering defrosting operation under the defrosting condition A when the cumulative heating operation
time has elapsed 30 minutes. It is 37 [45] minutes at SW3-1 OFF (factory default)
ii) It allows entering defrosting operation under the defrosting condition B when the cumulative heating operation
time has elapsed 20 minutes. It is 30 minutes at SW3-1 OFF (factory default)
iii) It allows entering defrosting operation when the outdoor heat exchanger temperature (Tho-R) and the suction
pressure saturated temperature (SST) are higher than normal.
Note (1) Figure in [ ] is for model 71.
-6
-20
-23
-27
-20 -18 -15 0 5 6 10-10 -5
-5
-10
-15
-25
-30
-25
Outdoor air temperature (°C) [Tho-A]
Outdoor heat exchanger temperature (°C) [Tho-R]
Defrost operation start
temperature zone
Defrost operation start temperature (Standard)
Defrost operation start temperature (SW3-1 ON)
-5
-10
-15
-20
-24
-25
-28.6
-30
-31
-35
-25 -20 -18 -15
Outdoor air temperature (°C) [Tho-A]
-10 -5 0 5 6 10
Suction suturated temperature (°C) [SST]
Defrost operation start
temperature zone
Defrost operation start temperature (SW3-1 ON)
Defrost operation start temperature (Standard for FDCW 100 models)
Defrost operation start temperature (Standard for FDCW 71 and 140 model)
Fig 4-2
Fig 4-1
Model 71-140
Model 71-140
Operation control function by the outdoor unit controller
Service
-
140
-

Mitsubishi MT300 Specifications

General

Brand	Mitsubishi
Model	MT300
Category	Heat Pump
Language	English