NREL
Temperatures exceeding thermostat deadbands
When running at 1 minute timesteps, the thermostat control with deadband can exceed the deadband limits. It's mainly an issue for the water heater, which can increase in temperature pretty quickly. It's an issue for HVAC too, but not as significant.
It'd be nice to add a feature to reduce the power of the equipment when it hits the top/bottom of the deadband. This would be similar to the ideal capacity algorithm, but not exactly the same. Maybe an algorithm like this:
- Determine thermostat mode (on/off)
- Determine ideal capacity using the top/bottom of the deadband depending on mode
- Set capacity to the ideal, capped at the min/max capacity of the equipment
Might need to think a little harder about this for HPWH and ASHP. But I think something should be able to work. It might even simplify the methods we have for ideal capacity now (at least for HPWH).
@jmaguire1 I think this covers the discussion around overshoot, right?
I think the process above works well, but we should also limit the max capacity further if the equipment starts as off. For example, if time_res is 1 minute and we hit the deadband limit at 30 seconds, then the max duty cycle should be 50%.
Yeah, I forgot we had this issue, but it definitely covers it.
I'll definitely have to test this with a HPWH when we do have an idea for a fix in place, I don't think it gets that much more complicated but maybe there's a point where there should be a HP>element switch that causes some issues?
