6 humidity control, Figure 22 humidity proportional band, Humidity control – Emerson Liebert iCOM User Manual

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Operation

3.6

Humidity Control

The control uses the humidity proportional band to determine which operation to perform (dehumidi-

fication/humidification) and how intensely to perform it. The Humidity Proportional Band is a user

defined range that is divided into two equal parts for dehumidifying and humidifying. The Humidity

Setpoint is located between these two equal parts.
An optional Humidity Deadband range can be defined, which is equally divided on either side of the

setpoint and separates the two halves of the proportional band. Figure 22 illustrates how the humid-

ity proportional band is evenly divided on either side of the humidity setpoint, with and without a

deadband.

Figure 22 Humidity proportional band

When the return air humidity deviates from the setpoint, it begins to penetrate one of the propor-

tional band halves, either dehumidification or humidification. If the return air humidity increases,

the control calls for 0% (none) to 100% (full) dehumidifying capacity, based on how far the humidity

penetrates the dehumidification portion of the proportional band. If the return air humidity

decreases, the control calls for 0% (none) to -100% (full) humidifying capacity based on how far the

humidity penetrates the humidification portion of the proportional band.
When the return air humidity reaches the end of the proportional band, either 100% or -100%, full

dehumidification or full humidification capacity is provided. No operation is performed when a 0%

call is calculated. The control varies the call for dehumidifying and humidifying in 1% increments as

the return air humidity moves through the proportional band halves.
The deadband range is used to widen the setpoint. When the return air humidity falls within the

deadband, the control operates the same as if the humidity equaled the setpoint exactly. This setting

helps maximize component life by preventing excessive component cycling. The Humidity Propor-

tional Band and Humidity Deadband parameters are in the Service menu under the Setpoints sub-

menu. The Humidity Setpoint parameter is in both the User menu and Service menu under

Setpoints.

Setpoint

+ 100%

Dehumidification

Dead-

band

Humidification

- Hum

+ Hum

Setpoint

½ Proportional Band

Dehumidification

- 100%

Humidification

- 100%

humidification

Without Deadband

With Deadband