Samsung AM080FX A Series Service Manual page 330

Piping Diagram
7-3 Functions (cont.)
7-3-2 Control (cont.)
7-3-2-5 Protective control (cont.)
Low Pressure Protection
▪ Purpose
Prevent abnormal low pressure to protect the system and compressors.
▪ Concept
The compressor operation frequency is lowered to increase the low pressure.
The Hotgas Bypass Valve is opened to bypass the high pressure to the suction pipe. This will increase the high pressure.
▪ Control specifications in detail
- Control of the operation frequency (see the chart in the previous page for pressure conditions.)
∙ 1st step Hz hold : Fix the current frequency if the discharge temperature is higher than 70℃ .
(It is possible to lower the frequency)
∙ 2nd step Hz down : Automatically lower the frequency by 5Hz at specified intervals if the discharge temperature is higher than 70℃ .
∙ 3rd step HP down : Automatically lower the frequency by 1Hz every second if the discharge temperature is higher than 70℃ .
∙ 4th step Comp trip : If in critical state for 3 min, stop the compressors and trigger an error (E410).
- Control of the Hot Gas Bypass Valve
Open the valve if low pressure is 3.2kgf/cm2,g or lower in cooling mode OR below 0.9kgf/cm2,g in heating mode.
Close the valve if low pressure is 4.2kgf/cm2,g or higher in cooling mode OR if low pressure is 1.7kgf/cm2,g or higher in heating mode.
- Others
If the outdoor temperature is abnormally low, limit opening of the valve. This reduces the need to repeatedly turn on the low pres-
sure protective control.
When cooling mode is on and the ambient temperature is 15℃ or lower, one of the Hz Hold through HP Down steps is activated if
the low pressure is -1kgf/cm2,g.
Cooling
Heating
-10℃ < Ta
-10℃ < Ta
-10℃ < Ta
※ Ta = Ambient Temperature
Samsung Electronics
Normal Operation
4.0
3.5
2.6
1.8
※ Compressor Trip release : Low Pressure > 3 kgf/ cm
Normal Operation
1.2
Ta -10℃,
2.0
0℃,
3.0
0℃ < Ta ,
1.0
Ta -10℃,
1.6
0℃,
2.2
0℃ < Ta ,
0.7
Ta -10℃,
1.2
0℃,
1.4
0℃ < Ta ,
0.5
Hz Hold area
Hz Down area
HP Down area
Compressor trip (E410) after staying
in this phase for a max of 3 min
Hz Hold area
Hz Down area
HP Down release
HP Down area
Compressor trip (E410) after staying
in this phase for a max of 3 min
Hz Hold release
Hz D own release
HP Down release
2 ,g for 3 min
Hz Hold release
Hz D own release
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