Mitsubishi Heavy Industries SRK20ZIX-S Service Manual page 63

(3) Defrosting operation
(a) Starting conditions (Defrosting operation can be started only when all of the following conditions are met.)
1) After start of heating operation
When it elapsed 45 (model 50 : 35) minutes. (Accumulated compressor operation time)
2) After end of defrosting operation
When it elapsed 45 (model 50 : 35) minutes. (Accumulated compressor operation time)
3) Outdoor heat exchanger sensor (TH1) temperature
When the temperature has been below –5ºC for 3 minutes continuously.
4) The difference between the outdoor air sensor temperature and the outdoor heat exchanger sensor temperature
¡ The outdoor air temperature ≧ 0°C ( model 50 : ≧ -2°C ) : 7°C or higher
¡ -15°C ≦ The outdoor air temperature ＜ 0°C (model 50 : ＜ -2°C) : 4/15 × The outdoor air temperature + 7°C or
higher
¡ The outdoor air temperature < -15°C : -5°C or higher
5) During continuous compressor operation
In addition, when the speed command from the indoor controller of the indoor unit during heating operation has count-
ed 0 rps 10 times or more and all conditions of 1), 2), 3) and 5) above and the outdoor air temperature is 3°C or less are
satisfied (note that when the temperature for outdoor heat exchanger sensor (TH1) is -5°C or less: 62 rps or more, -4°C
or less: less than 62 rps), defrost operation is started.
(b) Ending conditions (Operation returns to the heating cycle when either one of the following is met.)
1) Outdoor heat exchanger sensor (TH1) temperature: 13ºC (model 50 : 10°C) or higher
2) Continued operation time of defrosting → For more than 15 min.
2.6.9 Outline of cooling operation
(1) Operation of major functional components in Cooling mode
Compressor
Indoor fan motor
Outdoor fan motor
4-way valve
(2) Detail of control in each mode (Pattern)
(a) Fuzzy operation
During the fuzzy operation, the air flow and the compressor speed are controlled by calculating the difference between
the indoor temperature setting correction temperature and the retum air temperature.
Fan speed
Auto
HI
MED
LO
Thermostat ON
ON
ON
ON
OFF
Model
SRF25ZIX-S
20~72rps
20~72rps
20~48rps
20~34rps
Cooling
Thermostat OFF
OFF
ON
OFF
(few minutes ON) (few minutes ON)
OFF
SRF35ZIX-S SRF50ZIX-S
20~104rps 12~86rps
20~104rps 12~86rps
20~70rps 12~58rps
20~46rps 12~38rps
62
- -
Failure
OFF
OFF
OFF
OFF