How Does Voting and Heat/Cool Changeover Work in the CCP

Issue:

How Does Voting and Heat/Cool Changeover Work in the CCP

Resolution:

From VAV-SVU01A-EN pg 13:

https://tranesupport.zendesk.com/hc/en-us/articles/11744522945677-VariTrac-III-CCP-literature

 

Zone Heat/Cool Call Strength

After the heat/cool mode of the zone is decided, the strength of its heating or cooling call is determined.

Cool caller. A UCM becomes a cool caller if it is a voting UCM and its zone temperature is more than 1F above the active cooling setpoint. A UCM loses its cool caller status if it becomes a non-voter or if its zone temperature is less than the active cooling setpoint plus 0.5F.

Strong cool caller. A UCM becomes a strong cool caller if it is a voting UCM and its zone temperature is more than 2F above the active cooling setpoint. A UCM loses its strong cool caller status if it becomes a non-voter or if its zone temperature is less than the active cooling setpoint plus 1F.

Heat caller on a UCM with no local heat or Priority Local Heat edited to Off. A UCM becomes a heat caller if it is a voting UCM and its zone temperature is more than 1F below the active heating setpoint. A UCM loses its heat caller status if it becomes a non-voter or if its zone temperature is greater than the active heating setpoint minus 0.5F.

Strong heat caller on a UCM with no local heat or priority local heat edited to off. A UCM becomes a strong heat caller if it is a voting UCM and its zone temperature is more than 2F below the active heating setpoint. A UCM loses its strong heat caller status if it becomes a non-voter or if its zone temperature is greater than the active heating setpoint minus 1F.

Heat caller on a UCM with local heat and Priority Local Heat edited to On. A UCM becomes a heat caller if it is a voting UCM, its local heat has not been disabled by the CCP, and its zone temperature is more than 2F below the active heating setpoint. A UCM loses its heat caller status if it becomes a nonvoter or if its zone temperature is greater than the active heating setpoint minus 1.5F.

Strong heat caller on a UCM with local heat and Priority Local Heat edited to On. A UCM becomes a strong heat caller if it is a voting UCM, its local heat has not been disabled by the CCP, and its zone temperature is more than 3F below the active heating setpoint. A UCM loses its strong heat caller status if it becomes a non-voter or if its zone temperature is greater than the active heating setpoint minus 2F.

Heat/Cool Decision for the CCP

The central control panel scans all zones continuously (once every 10 to 20 seconds) and determines the quantity and the strength of all heating and cooling calls. At power-up and on transition from unoccupied to occupied, the greater number of heat or cool calls determines the mode of the CCP and the air conditioning system. If the votes are tied, the system defaults to heat. VAV-SVU01A-EN 15

Heat/Cool Changeover for the CCP

After the heating/cooling decision is determined, the VariTrac CCP requires a minimum number of opposite calls to change over. This is an editable setup parameter with a range of 1 to 4 (factory default is 2).  If there are no strong callers in the opposite mode, all current callers must be satisfied before the system is allowed to change over. A minimum time between changeovers is enforced. (The editable setup parameter has a range of 10 to 60 minutes; the factory default is 15 minutes.) The counter begins running immediately after a changeover occurs and must expire before changeover is allowed. The time remaining on the counter is displayed in the operator display and PC software.

Example: The Minimum Opposite Calls to Changeover is set to 2. If the system is in the heating mode and three zones are calling for heat, all three zones must be satisfied. The system changes over if two or more zones are calling for cooling and the changeover timer and all minimum-on/off times are satisfied.

Note: During the unoccupied mode (all groups unoccupied), the Minimum Opposite Calls to Changeover functions the same as in the occupied mode.

Heat/Cool Changeover from Opposite Strong Callers

A heat/cool changeover also occurs if enough opposite strong callers exist. (See Zone Heat/Cool Call Strength, p. 14.) Minimum Opposite Strong Calls to Changeover is an editable setup parameter with a range of 1 to 4 (factory default is 2). All current mode callers do not have to be satisfied, but the minimum time to changeover and all minimum on/off timers must expire before changeover is allowed.

Note: During the unoccupied mode (all groups unoccupied) the minimum opposite calls to changeover automatically changes to one (1), so any opposite strong caller can initiate a mode change even if there is a strong caller in the current mode.

 

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Notes:

 

Changes:

 

Other Question/Problem/Cause Statements:

• Heat/cool mode changeover in ccp system in the unoccupied mode

Facts:

• VariTrac III Central Control Panel (CCP)

Original wave: wave2589