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Update UnitarySystem set point control #10571

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Merged
mitchute merged 14 commits into from
Oct 31, 2025
Merged

Update UnitarySystem set point control #10571

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6f83135
Update UnitarySystem set point control
rraustad Jun 18, 2024
5fe7768
Merge branch 'develop' of https://github.com/NREL/EnergyPlus into 105…
rraustad Oct 22, 2025
bdf39dd
Fix unit tests
rraustad Oct 23, 2025
70c65fc
Merge branch 'develop' of https://github.com/NREL/EnergyPlus into 105…
rraustad Oct 23, 2025
3e23136
Removing these doesn't change answer. LastMode should hold last opera…
rraustad Oct 24, 2025
fd52405
Revert as much code and still get defect file to run
rraustad Oct 24, 2025
295e013
Merge branch 'develop' of https://github.com/NREL/EnergyPlus into 105…
rraustad Oct 24, 2025
281ef2d
Back out everything to start over
rraustad Oct 24, 2025
fd4d74b
Bare minimum to get UnitarySystem to turn on
rraustad Oct 24, 2025
4fc2af5
Add unit test, revert call to calcPassiveSystem in SP control function
rraustad Oct 27, 2025
6898bd6
Merge branch 'develop' of https://github.com/NREL/EnergyPlus into 105…
rraustad Oct 27, 2025
d44fccb
clang format
dareumnam Oct 29, 2025
1607d66
Merge branch 'develop' of https://github.com/NREL/EnergyPlus into 105…
dareumnam Oct 29, 2025
92357b7
Merge branch 'develop' into 10570-UnitarySystem-VS-coil-SP-not-working
mitchute Oct 31, 2025
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6 changes: 6 additions & 0 deletions src/EnergyPlus/UnitarySystem.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -7934,6 +7934,7 @@ namespace UnitarySystems {
thisSys.input_specs.design_specification_multispeed_object_name = Util::makeUPPER(it.value().get<std::string>());
}

thisSys.m_LastMode = (thisSys.m_CoolCoilExists) ? CoolingMode : HeatingMode;
thisSys.processInputSpec(state, thisSys.input_specs, sysNum, errorsFound, ZoneEquipment, ZoneOAUnitNum);

if (sysNum == -1) {
Expand Down Expand Up @@ -8234,6 +8235,11 @@ namespace UnitarySystems {
SingleDuct::SimATMixer(state, this->m_ATMixerName, FirstHVACIteration, this->m_ATMixerIndex);
}
}

// set variables used in fan call inside function calcPassiveSystem
state.dataUnitarySystems->m_massFlow1 = state.dataLoopNodes->Node(this->AirInNode).MassFlowRate;
state.dataUnitarySystems->m_runTimeFraction1 = (state.dataUnitarySystems->m_massFlow1 > 0.0) ? 1.0 : 0.0; // constant fan mode is required

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@rraustad rraustad Oct 24, 2025 •
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If either of these changes are removed, the system air flow goes to 0 and there is no control to set point temperature. I'm not quite sure the initialization of LastMode should be done in getInput but I am warming up to it since the mode needs to start somewhere. If the mode is not set from 0 to cooling or heating mode the fan does not turn on. So this change seems OK. And if the fan operating parameters are not set, for set point controlled systems, then the fan won't turn on. So this also seems OK.

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@mitchute mitchute Oct 27, 2025

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@rraustad do you think this is captured in our tests already? Given your description, it seems like we should have some sort of test to ensure this continues to function.

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@rraustad rraustad Oct 27, 2025

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This was hard to track down. The defect file has Fan:SystemModel in a modified example file (UnitarySystem_VSHeatPumpWaterToAirEquationFit). Unit tests have legacy fans. One unit test has Fan:System models but doesn't test controls. The Fan:SystemModel needs to set these 2 variables for the fan call in calcPassiveSystem. This may have started with the fan refactor or a change to UnitarySystem that did not notice this corner case. I'm trying to figure out a good place for a unit test.

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@rraustad rraustad Oct 27, 2025

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First 2 unit tests passed fine without any changes. Then figured out that it was the coil type and the fan type that caused this issue and a specific unit test was added. That unit test fails without these changes. This coil type was calling calcPassiveSystem when it did not need to. Those lines were deleted. Since that function is no longer called the new lines to set the fan parameters were also not needed.

if (this->OAMixerExists) {
// the PTHP does one or the other, but why can't an OA Mixer exist with the AT Mixer?
MixedAir::SimOAMixer(state, blankStdString, this->OAMixerIndex);
Expand Down