Emerson iCOM user manual Temperature Proportional Band, Temperature proportional band

Operation

3.3Temperature Control—Single Source Cooling (No Extra Cooling Coil)

3.3.1Temperature Proportional Band

The control uses the temperature proportional band to determine which operation to perform (cool- ing/heating) and how intensely to perform it. The Temperature Proportional Band is a user-defined range that is divided into two equal parts for cooling and heating. The Temperature Setpoint is between these two equal parts.

An optional Temperature 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 11 illustrates how the temperature proportional band is evenly divided on either side of the temperature setpoint, with and without a deadband.

Figure 11 Temperature proportional band

With Deadband

When the return air temperature deviates from the setpoint it begins to penetrate one of the propor- tional band halves, cooling or heating. If the return air temperature increases, the control calls for 0% (none) to 100% (full) cooling capacity based on how far the temperature penetrates the cooling portion of the proportional band. If the return air temperature decreases, the control calls for 0% (none) to - 100% (full) heating capacity based on how far the temperature penetrates the heating portion of the proportional band.

When the return air temperature reaches the end of the proportional band, either 100% or -100%, full cooling or full heating capacity is provided. No operation is performed when a 0% call is calculated. The control varies the call for cooling and heating in 1% increments as the return air temperature moves through the proportional band halves.

The deadband range is used to widen the setpoint. When the return air temperature falls within the deadband, the control operates the same as if the temperature equaled the setpoint exactly. This set- ting helps maximize component life by preventing excessive component cycling. The Temperature Proportional Band and Temperature Deadband parameters are in the Service menu under the Set- points submenu. The Temperature Setpoint parameter is in both the User Menu and Service Menu under Setpoints.

There is a parameter AutoSet Enable (Service Menu, Setpoints), which automatically sets the propor- tional bands for temperature and humidity, and both the integration time factors according to the type of unit (Chilled Water, single or double compressor), with influence of the selected Teamwork Mode. See 4.1 - Teamwork Modes for more on using this feature.

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