Revision history [back]

In the table output, the last subtable in the ABUPS reports is "Comfort and Setpoint Not Met Summary" which shows 1000s of hours for cooling/heating setpoint not met. So, why isn't the HVAC operating in this file? Took a little bit to find this:

AirLoopHVAC:UnitarySystem,
< . . . >
,                        !- Cooling Supply Air Flow Rate Method
,                        !- Cooling Supply Air Flow Rate {m3/s}
,                        !- Cooling Supply Air Flow Rate Per Floor Area {m3/s-m2}
,                        !- Cooling Fraction of Autosized Cooling Supply Air Flow Rate
,                        !- Cooling Supply Air Flow Rate Per Unit of Capacity {m3/s-W}
,                        !- Heating Supply Air Flow Rate Method
,                        !- Heating Supply Air Flow Rate {m3/s}
,                        !- Heating Supply Air Flow Rate Per Floor Area {m3/s-m2}
,                        !- Heating Fraction of Autosized Heating Supply Air Flow Rate
,                        !- Heating Supply Air Flow Rate Per Unit of Capacity {m3/s-W}
,                        !- No Load Supply Air Flow Rate Method

The unitary system flow rates are all zero. This should be more like

SupplyAirFlowRate,                        !- Cooling Supply Air Flow Rate Method
autosize,                        !- Cooling Supply Air Flow Rate {m3/s}
,                        !- Cooling Supply Air Flow Rate Per Floor Area {m3/s-m2}
,                        !- Cooling Fraction of Autosized Cooling Supply Air Flow Rate
,                        !- Cooling Supply Air Flow Rate Per Unit of Capacity {m3/s-W}
SupplyAirFlowRate,                        !- Heating Supply Air Flow Rate Method
autosize,                        !- Heating Supply Air Flow Rate {m3/s}
,                        !- Heating Supply Air Flow Rate Per Floor Area {m3/s-m2}
,                        !- Heating Fraction of Autosized Heating Supply Air Flow Rate
,                        !- Heating Supply Air Flow Rate Per Unit of Capacity {m3/s-W}
SupplyAirFlowRate,                        !- No Load Supply Air Flow Rate Method
autosize,                        !- No Load Supply Air Flow Rate {m3/s}

So, why no defaults? Because AirloopHVAC:UnitarySystem is a multipurpose wrapper which may or may not include a fan, might be heating-only, or cooling-only, etc. So, it doesn't really know it's place in life and does whatever the user asks for, in this case, nothing. But, in this case, if it holds a fan, a cooling coil, and a heating coil, and ends up with all zero airflow rates - that should be enough to throw a warning. New issue 7166 posted to request some warnings.

Once this is fixed, I would also recommend the following for this model:

1. Use Control Type = Load instead of Setpoint, specify the control zone here in the unitary system, and ditch the (awful) SetpointManager:SingleZone:Reheat objects.
2. Set the availability manager schedules to be always on. The UnitarySystem Fan Operating Mode Schedule will switch between continuous fan and cycling fan and with Load-based controls it won't run unless the thermostat calls for heating or cooling during the cycling fan hours.
3. Remove the schedules from all of the coil objects - the controls will operate the coils only as needed. Overscheduling can cause problems during unoccupied hours if the system needs to run, the coils won't be available.