Outline Of Heating Operation - Mitsubishi Heavy Industries SRK20ZG-S Tech Manual

4.9 Outline of heating operation

(1) Operation of major functional components in heating mode
Compressor
Indoor fan motor
Outdoor fan motor
4-way valve
(2) Details of control at each operation mode (pattern)
(a) Fuzzy operation
Deviation between the room temperature setting correction temperature and the suction air temperature is calculated in
accordance with the fuzzy rule, and used for control of the air capacity and the inverter speed.
Fan speed
Auto
HI
MED
LO
When the defrosting, protection device, etc. is actuated, operation is performed in the corresponding mode.
(b) Hot keep operation
If the hot keep operation is selected during the heating operation, the indoor blower is controlled based on the temperature of
the indoor unit heat exchanger (detected with Th2, indoor unit heat exchanger sensor) to prevent blowing of cool wind.
(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 minutes (35, 50 type : 35 minutes). (Accumulated compressor operation time)
2 After end of defrosting operation
When it elapsed 45 minutes(35, 50 type : 35 minutes). (Accumulated compressor operation time)
3 Outdoor unit heat exchanger sensor (Th4) temperature
When the temperature has been below –5ºC for 3 minutes continuously.
4 The difference between the outdoor air sensor temperature and the outdoor unit heat exchanger sensor temperature
¡ The outdoor air temperature ≥ _ -17°C : 7°C (35type : 5°C, 50type : 4°C) on higher
¡ The outdoor air temperature < -17°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 counted
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 Th4 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 (Th4) temperature: 13ºC or higher
2 Continued operation time of defrosting → For more than 10 min.
Thermostat ON
ON
ON
ON
ON
Model
SRK20ZG-S
30~100rps
30~100rps
30~70rps
30~44rps
Heating
Thermostat OFF
OFF
ON(HOT KEEP)
OFF
(few minutes ON)
ON
SRK25ZG-S SRK35ZG-S
30~102rps
30~102rps
30~72rps 30~84rps
30~54rps 30~62rps
17
- -
Defrost Failure
OFF OFF
OFF OFF
OFF OFF
OFF
OFF
(3 minutes ON)
SRK50ZG-S
15~122rps
15~122rps
15~84rps
15~66rps