Samsung AM072BXV Series Service Manual page 266

Piping Diagram
7-3 Functions (cont.)
7-3-2 Control (cont.)
7-3-2-5 Protective control (cont.)
Freezing prevention
▪ Purpose
Prevent frost in indoor units to protect compressors. Prevent other accidents.
If there is frost in indoor units, refrigerant will not evaporate. As a result, compressor failure will occur due to liquid compression.
If there is frost in indoor units, ice may form and fall causing an accident.
▪ Concept
- Frost is detected based on the temperature of indoor unit heat exchangers.
- The compressor frequency is lowered to prevent frost in indoor unit heat exchangers.
- The temperature for indoor unit heat exchangers is defined during frost preventive control:
- Minimum temperature of temperature at the exit of indoor unit heat exchangers and temperature at the entrance of indoor unit heat
exchangers)
▪ Control specifications in detail
- The compressor operation frequency is controlled according to the temperature of indoor unit heat exchangers, as shown below.
1st step Hz hold : The current frequency is fixed. (It is possible to lower the frequency if necessary)
2nd step Hz down : The frequency is forcibly lowered by 5Hz at specified intervals.
3rd step HP down : The frequency is forcibly lowered by 1Hz every second.
4th step Comp stop : Compressors stop and the fan speed changes for indoor units to the mid level.
Temperature (℃)
7
4
2
0
-2
-4
Samsung Electronics
Normal Operation
Hz Hold area if in this state for 40 sec
Hz Down area if in this state for 40 sec
HP Down area if in this state for 40 sec
Compressor Stop & Indoor unit air flow = low if in this state for 40 sec
Compressor Stop & air flow release
Hz Hold & HP down release
260