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Zone temperatures not matching setpoints during the night

asked 2017-07-28 14:25:58 -0500

map1995's avatar

updated 2017-07-28 16:19:21 -0500

Using designbuilder to create the model...

I am trying to track zone temperatures for various cooling setpoint schedules. Time after time, the zone temps will match the thermostat setpoint throughout the entire day, and then from 9:00pm-6:00am, the zone temperature will rise to 25 degC and just stay there, despite what my thermostat setpoint is. Is there some setting in the model that is causing this to happen? I can't seem to find anything that would cause the model to do this during this time range.

Any suggestions would be appreciated.

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answered 2017-07-29 02:45:41 -0500

Dave's avatar

If Molly's suggestion isn't the reason in this case, take a look at your "setback" temperature, and the timing of related HVAC schedules which have a value of 0.5 (which would trigger operation to the setback temp not setpoint temp). The reason I suggest that is that you suggest the temp is fairly constant at 25C outside normal setpoint times. If neither works then I suggest you submit a ticket to the Support Desk with the model and they should be able to resolve it.

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answered 2017-07-28 14:51:56 -0500

Molly Curtz's avatar

updated 2017-07-28 14:52:49 -0500

Most likely your system (fan schedule) is off so it cannot provide air to meet the load. Do you have system flow at these hours? Look at your fan schedule and also check your inputs for night cycle control. Night cycle control can allow the fan to cycle on when there is a thermostat call from the zones served, even if the fan schedule value is OFF (zero).

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Asked: 2017-07-28 14:25:58 -0500

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Last updated: Jul 29 '17