Protective Control Function - Mitsubishi Heavy Industries SRK20ZD-S1 Technical Manual

(12) Protective control function

(a) Frost prevention for indoor heat exchanger (During cooling or dehumidifying)
(i) Operating conditions
(i) Indoor heat exchanger temperature sensor (detected with Th2) is lower than 2.5ºC.
(ii) 10 minutes elapsed after the start of operation.
(ii) Detail of frost prevention operation
Compressor
Indoor fan
Outdoor fan
4-way valve
(iii) Reset conditions: Indoor heat exchanger temperature sensor (Th2) is higher than 8ºC.
(b) 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.
(c) Three-minute forced operation
When the compressor begins operating the thermal operation is not effective for 3 minutes, so operation continues as is in the
operation mode. (After 3 minutes has passed the thermal operation is effective.)
However, stopping the compressor via a stop signal or protection control has priority.
(d) High-pressure control
The indoor heat exchanger temperature sensor detection temperature controls the outdoor fan and compressor.
¡ When the indoor heat exchanger
temperature is = > 58˚C
ON
Outdoor fan
Indoor heat exchanger temp. (˚C)
(e) Heating overload protective control
(i) Operating conditions: when the unit is heating with the compressor is on, and the outdoor air temperature rose beyond 17°C
(ii) Detail of operation: indoor fan speed is raised forcibly by 1 step.
(iii) Reset conditions: when the outdoor air temperature drops below 16°C.
(f) Abnormality of outdoor unit
(i) Cooling operation
When the indoor heat exchanger temperature does not fall to 25°C or below for 40 minutes after 5 minutes have elapsed since
the compressor operation start, the abnormality stop occurs. (The timer light flashes 2 times.)
(ii) Heating operation
1 The indoor heat exchanger temperature < 5°C for 5 minutes and more
The unit is stopped due to the outdoor unit abnormality excepting the defrost operation time. (The timer light flashes 2
times.)
2 5°C < = the indoor heat exchanger temperature < 30°C for 40 minutes and more
When the indoor heat exchanger temperature does not rise to 30°C or over for more than 40 minutes after 5 minutes have
elapsed since the compressor operation start, the abnormality stop occurs. However, when the indoor fan began operation
once, this function is not activated until the unit is stopped or the mode is changed. (The timer light flashes 2 times when
20 minutes have elapsed.)
OFF
Protects the fan tap just before frost prevention control.
OFF
Stop mode
OFF
48 58
for 30 seconds continuously.
¡ When the indoor heat exchanger
temperature is = > 62˚C
ON
Compressor
Indoor heat exchanger temp. (˚C)
193
- -
OFF
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