Liebert iCOM Microprocessor TM-10098 - Manual (Page 33)

iCOM
Controls Training and Service Manual
The humidity controller activates the first stage of dehumidification operation when
the return air humidity level increases to 50% of the humidity proportional band.
The second stage of dehumidification is activated when the return air humidity
level increases to 100% of the humidity proportional band.
The humidity controller deactivates the second stage of dehumidification operation
when the return air humidity level decreases to 50% of the humidity proportional
control band value. The first stage of dehumidification is deactivated when the
return air humidity level decreases to the humidity set point of 50% or 0% of the
humidity proportional band.
If the compressors have unloading capability (4-stage cooling), then the
compressors are activated in the fully loaded condition for each stage of
dehumidification.
2 Stage Compressorized Dehumidification – No Dead Band
Humid Set Point: 50%
Proportional Band: 8%
50 51 52 53 54 55
Increasing Humidity
Dehumid
Stage 2 Off
Humidity Set Point + (1/2 Proportional Band)
Dehumid
Stage 1 Off
Dehumid
Stage 1 On Dehumid
Stage 2 On
Note: in the above example that the control band begins at the 50% humidity set
point and has a length of 4%, which is ½ of the programmed humidity proportional
band value.
As the return air humidity level increases, first stage dehumidification operation is
activated at 52%RH or 50% of the dehumidification control band. If the return air
humidity level continues to increase the second dehumidification stage actives at
54%RH, which 100% of the dehumidification control band.
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