This problem is occurring in v8.7. For a model with a hot water loop serving VAV:reheats throughout a building, setpoint is met as expected using a constant speed pump with intermittent control where a large majority of the flow is going to bypass. When I switch to a VFD pump, using the same design parameters, the loop stops making setpoint and boiler energy use increases significantly. Has anybody dealt with this issue before, or can anyone provide some insight on where I should be looking for incompatibilities? Thanks!
Things I've tried so far with no change in results:
Baseline model is using a gas boiler on the "NotModulated" setting. I tried both NotModulated and "LeavingSetpointModulated" forcing the same setpoint at the boiler as with the loop setpoint manager.
Changing the VFD pump from intermittent control to continuous.
Using the headered VFD pump object with just one pump in the bank and identical design parameters.
With the VFD pump, no flow is going to bypass, but I still tried a run with both supply and demand bypass disabled.
Comparison of results:
