Setting a temperature dead band in OpenStudio

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Hello @mattkoch. I defined static cooling and heating setpoints in the Thermal Zone tab: cooling setpoint = 75F, heating setpoint = 69F. I ran the simulation for a few days in the summer, and the temperature remained steady throughout. My original building model is made up of an unconditioned crawlspace, conditioned main floor, & unconditioned attic.

But I noticed that there was a temperature fluctuation when I reduced the building model to just the conditioned main floor. Both have exactly the same construction materials so I'm not sure why this is happening. The post is updated to show this

I suppose your building is on the southern half, with high temperatures in January? The profile on the right might be expected with a 75/69 heat/cool combination when the climate zone is such that there is enough cooling/heating load during the day/night to require cooling/heating. HOWEVER, your nighttime OA only drops to 24 C, and the main floor should not drop below that. You could plot the cooling and heating rate profiles on your cooling and heating coils - they should support the temperature profile.

The profile on the left may be more realistic in that regard - there are in fact tiny drops on 1/3 and 1/6, but other than that, cooling is likely required day and night to maintain 24 C, though at lesser cooling power at night than during the day. You might want to run a few days in June to verify that temperature indeed drops to 20.5 C and heating is needed most of the time. Now, back to the right, is it possible that your cooling coil is on at full cooling power 24/7. Again, plot your cooling and heating coil rates (or air flow rates) to verify proper modulation.

@mattkoch the building is in Texas and the simulation period is actually a week in August, but DViewer, always defaults to the beginning of the year. The heating setpoint is 20.6C, which is the minimum temperature on the right. The cooling power mimics outdoor temperature and heating is flat. I will re-run the simulation and post screenshots. Thank you.

@mattkoch I plotted the heating and cooling rates (see original post). Even though both cases have the same HVAC system and the same materials, the model on the right seems to have a less efficient HVAC system as the heating coil comes on sometimes. Peak cooling load is 2.2kW on the LHS and 3.2kW on the RHS. I would have expected it to be less with a smaller geometry. Do you know why this may be happening?