Liebert TM-10098 Operations and Charts, Humidifier Operation, Relative Humidity Control

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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