Emerson Liebert ICOM-DO Service Manual download pdf (Page 27)

iCOM

Controls Training and Service Manual

Relative Humidity Control

Relative humidity control is based on the humidity content in the return air. The

iCOM microprocessor control determines the unit humidification/ dehumidification

operation by comparing the return air humidity value to the control band that is

determined by the:

• Programmed humidity set point in %RH

• Programmed humidity proportional band in %RH

Operations and Charts

The humidity proportional control band value is divided into two parts: the humidity

set point plus ½ of the programmed humidity proportional band for

dehumidification operation and the humidity set point minus ½ of the programmed

humidity proportional band for humidification operation.

A humidity dead band can also be programmed into the control to shift the

humidification and/ or dehumidification on/ off operations away from the humidity

set point.

This programmed humidity dead band value is divided into two parts: the humidity

set point plus ½ of the dead band – no dehumidification operation and the humidity

set point minus ½ of the band – no humidification operation.

The humidity set point range is adjustable from 1 – 80% RH in increments of 1%

RH. The humidity proportional band range is adjustable from 1 – 20% RH in

increments of 1% RH. The humidity dead band range is adjustable from

0 – 50% RH in increments of 1% RH.

Humidifier Operation

The Relative Humidity control program is used to illustrate the humidification

operation in the following examples. The basic humidification control band is

established at the humidity set point with the length equal to ½ of the programmed

humidity proportional band value. The Liebert DS units are supplied with an

infrared humidifier rated at the unit capacity.

The humidity controller activates the infrared humidifier when the return air

humidity level decreases to 100% of the humidity proportional band. The

humidifier makeup water solenoid valve also operates during humidification

operation based on a timing sequence.

The humidity controller deactivates the infrared humidifier and makeup water

solenoid valve when the return air humidity level increases to 50% of the humidity

proportional control band value.

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Emerson Liebert ICOM-DO Service Manual Page 27