Protective Control Function - Mitsubishi Heavy Industries SRK20ZFX-S Technical Manual

4.14 Protective control function

(1) Frost prevention for indoor heat exchanger (During cooling or dehumidifying)
(a) Operating conditions
(i) Indoor heat exchanger temperature (detected with Th2) is lower than 5ºC.
(ii) 10 minutes after reaching the inverter command speed except 0 rps.
(b) Detail of anti-frost operation
Indoor heat exchanger
Item
Indoor command speed
Indoor fan
Outdoor fan
4-way valve
(c) Reset conditions: After 5 minutes of operation, the indoor heat exchanger
temperature (Th2) is 8ºC or higher.
(2) Indoor fan motor protection
When the air conditioner is operating and the indoor fan motor is turned ON, if the indoor fan motor has operated at 300 rpm or
under for more than 30 seconds, the unit enters first in the stop mode and then stops the entire system.
TIMER light illuminates simultaneously and the RUN light flashing 6 times at each 8-second.
(3) Dew condensation prevention control [Cooling (including automatic), cooling oriented dehumidifying operation)
◆ SRK50ZFX-S
(a) Operating conditions: When the following conditions are met after 20 minutes or more of continuous operation after
1 The command speed is 28 rps or higher
2 The humidity sensor value is 68% or higher
(b) Operation contents
Item
Fan Speed Medium
Fan Speed Low
Other Settings
(c) Reset conditions: When either of the following conditions is satisfied.
1 The command speed is lower than 28 rps.
2 The humidity sensor value is less than 63%.
(4) Prevention of continuous low speed operation: For oil return to compressor
(a) Operating conditions: When command speed of less than 30(26) rps continues for 8(60) minutes
(b) Detail of operation: The unit is operated at command speed of 30 rps forcibly for 15 seconds. (The indoor and outdoor
Notes (1) When the command of exceeding 30 rps is directed during 30 rps forced operation, the unit follows it.
Note (2) Values in ( ) are for Type 50.
(5) Compressor protection start
(a) When the indoor unit calculated speed is 64 rps or over at operation start, the unit is operated with 64 rps for 1 minute and 45
seconds. (All models) After that when the calculated speed is 96 rps or over, the unit is operated with 96 rps for 5 minutes
then moved to command speed. (50 type only)
(b) At thermo operation (OFF → ON) this control is not executed.
(c) The indoor unit fan corresponds to the command speed of each operation mode.
Note (1) When the calculated speed is less than 64 rps, the unit is started with low load starting described in article (6).
temperature
5°C or lower
20: Max 38 rps
25: Max 42 rps
35: Max 56 rps
50: Max 65 rps
Depends on operation mode
Depends on operation mode
OFF
operation starts.
Type
Indoor fan speed
Indoor fan speed
Indoor fan speed Corresponding to command speed
fans are not changed.)
2.5°C or lower
0rps
Max 2nd
OFF
Depends on stop mode
SRK50ZFX-S
4th speed
4th speed
22
- -
Inverter
command
speed
Upper limit
speed
0 rps
2.5 5
Indoor heat exchanger
temperature (°C)
Inverter command speed at upper limit
30 rps
50 rps
68 73
Humidity (%)
8