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MDC tech
12-30-2010, 07:14 AM
System has 25 ton RTU, bypass damper, parallel fan-powered boxes, digital thumb wheels, and the CCP. Two issues.

One, with the thumb wheel enabled the occ set points do not revert back to the CCP settings after an occupancy change. Can this be done?

Two, when all groups are unoccupied and satisfied the VAV fans do not shutdown. The only way to get it to go off is to override the box to 0%.
milkyway
12-30-2010, 09:07 AM
vari trac is on a a voteing system., if u are familiar with it u can change the vote system
MDC tech
12-30-2010, 06:57 PM
I am aware of the polling process. How does taking out a box from the vote help me?
milkyway
12-31-2010, 09:31 AM
not sure why u want to take out a box
as far as question 2.,.,that i amsuming that that would be in the configuration., might take a bit to find what exactly and where the parameters are exactly.,
MDC tech
12-31-2010, 11:18 AM
i have been through all the parameters meticulously with no luck. we are waiting for answers from trane. I know trane is concerned about fans spinning backwards with the parallel boxes so I'm expecting them to tell they will all run continuously even during unoccupied times. As for as the thumb wheel is concerned the only choice we have at this time is to leave them disabled so it follows the set points in the CCP.
mallron
01-01-2011, 07:08 PM
If thumbwheels are enabled then they will always be enabled until changed by the operator.

The parallel fans should be off unless the box is heating the space, regardless of occupany. Why would anyone be concerned with the fans running backwards?
MDC tech
01-03-2011, 08:00 AM
its unfortunate the the digital thumb wheels don't have a temporary setting.

This building has all the returns ducted. So all the fans must run simultaneously. I just need all the fans to shut down when all the boxes are unocc.
MDC tech
01-03-2011, 04:16 PM
Correction these are Fan powered series boxes.
ISAMemphis
01-03-2011, 08:38 PM
Which CCP is it? old or newer
mallron
01-03-2011, 09:03 PM
Ok, series fans should turn off when the boxes go unoccupied unless the space reaches one of the unoccupied setpoints.

What do you mean by "override the box to 0%"?
MDC tech
01-04-2011, 06:59 AM
The damper position can be overridden from the CCP.
If I drive it to 0% the boxes fan will shut off. This is the only way I can get them to shut off.