Having let the default reporting tolerance (a very low value of 0.2C), I was getting a lot of unmet cooling hours.
After investigation, the ZoneHVAC equipment (ZoneHVAC:WaterToAirHeatPump) is producing a space temperature that is constantly roughly 0.5C above setpoint.
This is reported in Detailed timestep for a week in July:
For my ZoneHVAC:WaterToAirHeatPump I've set an Availability schedule of Always 1, and for the Supply Air Fan Operating Mode Schedule to Always 0, meaning I want a cycling fan that will turn on only as needed to meet the load. From the doc:
Schedule values of 0 denote that the supply air fan and the heating or cooling coil cycle on and off together to meet the heating or cooling load (a.k.a. AUTO fan)
What is causing my space temperature to be constantly about 0.5C above the setpoint? How can I correct this?
(I know I can just increase the reporting tolerance to let the unmet hours go away but I'm interested in finding out why that's happening)
I initially thought it could be two things:
- Either this is just due to the Building's Temperature Converge Tolerance Value that has a default of 0.4C
- Lowering that temperature to 0.2C didn't change anything
- Or this may be a very similar issue as the one I posted here and where it was rightfully pointed out to me that this was because of the
AvailabilityManager:NightCyclereporting tolerance of 1C by default. I'm thinking having set the Supply Air Fan schedule to always 0 might be triggering some built in availability manager with a hardcoded tolerance of 1C- Setting an Always 1 schedule for the supply air fan didn't help either
