Question-and-Answer Resource for the Building Energy Modeling Community
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Hi Jacob,
I think I identified a problem but not the full solution for it. If you check the zone temperature during summer period you'll see that during unoccupied period the zone is cooled down to 15C which is actually your heating setback temperature. To achieve such a low temperature the supply air has to be sub-cooled to 5C which, as you mentioned, is unrealistic. I cannot source the root of this issue.
The partial solution is to control the zone conditions by single heating and single cooling thermostats. As soon as I changed to single cooling thermostat during summer period, the system behaves as it should (supply air temperature around 15C, zone air temperature according to cooling occupied/unoccupied setpoints).
Another possible way of overriding the issue is to replace Fan:OnOff with Fan:ConstantVolume and keep DualSetpoint control. This doesn't completely remove periods when the supply air temperature is around 5C, although it significantly reduces it.
I hope you'll find this answer useful.
Best regards, IK
