Liebert iCOM Microprocessor TM-10098 - Manual (Page 31)

iCOM
Controls Training and Service Manual
Dehumidification Operation
The Relative Humidity control program is used to illustrate the dehumidification
operation in the following examples. The basic dehumidification control band is
established at the humidity set point with the length equal to ½ of the programmed
humidity proportional band value.
The humidity controller activates dehumidification operation when the return air
humidity level increases to 100% of the humidity proportional band. The humidity
controller deactivates dehumidification operation when the return air humidity level
decreases to 0% of the humidity proportional control band value.
1-Stage Dehumidification, Compressorized Direct Expansion (DX)
Systems
The Liebert DS unit is supplied with two (2) compressors. Under normal
operation, the lead compressor is used for sensible cooling and the lag
compressor is used for either additional cooling or for dehumidification control.
The optional hot gas bypass solenoid valve is de-energized during
dehumidification.
If single compressor dehumidification is selected, the lag compressor is activated
by the humidity controller when the return air humidity level increases to 100% of
the humidity proportional band.
The humidity controller deactivates the lag compressor when the return air
humidity level decreases to 50% of the humidity proportional control band value.
1 Stage Compressorized Dehumidification – No Dead Band
Humid Set Point: 50%
Proportional Band: 8%
50 51 52 53 54 55
Increasing Humidity
Dehumidification On
Dehumidification Off
Humidity Set Point - (1/2 Proportional Band)
30