2 Stage Compressorized Cooling – With Dead Band

iCOM Control Training and Service Manual

2 Stage Compressorized Cooling – With Dead Band

Temp Set Point + (1/2 Dead Band + 1/2 Proportional Band)

Temp Set Point: 70°F

 

 

 

 

Proportional Band: 8°F

 

 

 

 

Dead Band: 2°F

 

 

Cool 1 On

 

Cool 2 On

 

 

 

 

 

 

 

 

 

70

71

72

73

74

75

DB

 

 

 

 

 

 

Cool 1 Off

Cool 2 Off

 

 

 

 

Increasing Temperature

Note: in the above example that the control band begins at the 70°F temperature set point and has a length of 5°F, which is ½ of the programmed temperature dead band value plus ½ of the programmed temperature proportional band value.

As the return air temperature increases Cooling 1 (lead compressor) is activated at 73°F or ½ of the dead band value plus 50% of the cooling control band. If the return air temperature continues to increase Cooling 2 (lag compressor) will activate at 75°F or ½ of the dead band value plus 100% of the cooling control band.

When the return air temperature starts to decrease, Cooling 2 (lag compressor) is deactivated at 73°F or ½ of the dead band value plus 50% of the cooling control band and Cooling 1 (lead compressor) is deactivated at 71°F or ½ of the dead band value plus 0% of the cooling control band.

Remember the temperature dead band value is used by the control to shift the cooling on/ off operations away from the temperature set point.

Optional 4 - Stage Cooling, Two (2) Compressors with Unloaders

The basic temperature cooling control band is established at the temperature set point with the length equal to ½ of the programmed temperature proportional band divided by the number of cooling stages.

The Liebert DS units are supplied with two (2) compressors, each compressor is rated at ½ of the unit capacity. Each compressor will be the semi-hermetic type

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Liebert TM-10098 service manual Stage Compressorized Cooling – With Dead Band, iCOM Control Training and Service Manual