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Use fan RTF only for cycling fan impact on AFN distribution losses #11571

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Use fan RTF only for cycling fan impact on AFN distribution losses #11571

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17c9345
Only use fan RTF for cycling fan impact on AFN.
lymereJ May 1, 2026
628967c
Clang!
lymereJ May 2, 2026
0ee296b
Test from #11491.
lymereJ May 4, 2026
e83cd80
Merge branch 'develop' into fix_unitary_system_afn_runtime_fracs_alt
mitchute May 4, 2026
ad38b0c
format [ci skip][decent_ci_skip]
mitchute May 5, 2026
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13 changes: 3 additions & 10 deletions src/EnergyPlus/AirflowNetwork/src/Solver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -201,9 +201,7 @@ namespace AirflowNetwork {
if (FirstHVACIteration) {
if (allocated(m_state.dataAirLoop->AirLoopAFNInfo)) {
for (i = 1; i <= DisSysNumOfCVFs; i++) {
m_state.dataAirLoop->AirLoopAFNInfo(i).AFNLoopHeatingCoilMaxRTF = 0.0;
m_state.dataAirLoop->AirLoopAFNInfo(i).AFNLoopOnOffFanRTF = 0.0;
m_state.dataAirLoop->AirLoopAFNInfo(i).AFNLoopDXCoilRTF = 0.0;
m_state.dataAirLoop->AirLoopAFNInfo(i).LoopOnOffFanPartLoadRatio = 0.0;
}
}
Expand Down Expand Up @@ -9794,14 +9792,9 @@ namespace AirflowNetwork {
// Hard code here
PartLoadRatio = m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).LoopOnOffFanPartLoadRatio;
LoopPartLoadRatio(AirLoopNum) = m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).LoopOnOffFanPartLoadRatio;
OnOffFanRunTimeFraction = max(m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF,
m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopOnOffFanRTF,
m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopDXCoilRTF);
LoopOnOffFanRunTimeFraction(AirLoopNum) = max(m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF,
m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopOnOffFanRTF,
m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopDXCoilRTF);
}
m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF = 0.0;
OnOffFanRunTimeFraction = m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopOnOffFanRTF;
LoopOnOffFanRunTimeFraction(AirLoopNum) = m_state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopOnOffFanRTF;
}
Comment on lines +9795 to +9797
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@lymereJ lymereJ May 4, 2026

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Only use fan RTF instead of the maximum of the coils and the fan RTF. All functioning air loops should have fans and when fans are cycling their RTF is the same as the coils.

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@mitchute mitchute May 5, 2026

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That makes sense to me.


if (DisSysCompCVFData(FanNum).fanType == HVAC::FanType::OnOff && LoopPartLoadRatio(AirLoopNum) < 1.0) {
for (std::size_t i = 0; i < linkReport.size(); ++i) {
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5 changes: 0 additions & 5 deletions src/EnergyPlus/Coils/CoilCoolingDX.cc
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Expand Up @@ -787,11 +787,6 @@ void CoilCoolingDX::simulate(EnergyPlusData &state,
// DataAirLoop::LoopDXCoilRTF = max(this->coolingCoilRuntimeFraction, DXCoil(DXCoilNum).HeatingCoilRuntimeFraction);
state.dataAirLoop->LoopDXCoilRTF = this->coolingCoilRuntimeFraction;
state.dataHVACGlobal->DXElecCoolingPower = this->elecCoolingPower;
if (this->airLoopNum > 0) {
state.dataAirLoop->AirLoopAFNInfo(this->airLoopNum).AFNLoopDXCoilRTF = this->coolingCoilRuntimeFraction;
// The original calculation is below, but no heating yet
// max(DXCoil(DXCoilNum).CoolingCoilRuntimeFraction, DXCoil(DXCoilNum).HeatingCoilRuntimeFraction);
}

// report out to the coil sizing report if needed
if (this->reportCoilFinalSizes) {
Expand Down
13 changes: 0 additions & 13 deletions src/EnergyPlus/Furnaces.cc
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Expand Up @@ -213,12 +213,6 @@ namespace Furnaces {
state.dataFurnaces->GetFurnaceInputFlag = false;
}

// Save the current AFNLoopHeatingCoilMaxRTF for comparison with the one calculated below
Real64 refAFNLoopHeatingCoilMaxRTF(0.0);
if (state.afn->distribution_simulated) {
refAFNLoopHeatingCoilMaxRTF = state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF;
}

// Find the correct Furnace
if (CompIndex == 0) {
FurnaceNum = Util::FindItemInList(FurnaceName, state.dataFurnaces->Furnace);
Expand Down Expand Up @@ -705,8 +699,6 @@ namespace Furnaces {
ShowContinueError(state, EnergyPlus::format("...occurs for {}", thisFurnace.Name));
errorFound = false;
}
state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF =
max(refAFNLoopHeatingCoilMaxRTF, heatingCoilRTF, suppHeatingCoilRTF);
}

// Reset OnOffFanPartLoadFraction to 1 in case another on/off fan is called without a part-load curve
Expand Down Expand Up @@ -5856,11 +5848,6 @@ namespace Furnaces {
SetOnOffMassFlowRate(state, FurnaceNum, AirLoopNum, OnOffAirFlowRatio, fanOp, ZoneLoad, MoistureLoad, PartLoadRatio);
}
}

// AirflowNetwork global variable
if (state.afn->distribution_simulated) {
state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF = 0.0;
}
}

void SetOnOffMassFlowRate(EnergyPlusData &state,
Expand Down
16 changes: 0 additions & 16 deletions src/EnergyPlus/HeatingCoils.cc
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Expand Up @@ -1894,18 +1894,6 @@ namespace HeatingCoils {
heatingCoil.OutletAirEnthalpy = Psychrometrics::PsyHFnTdbW(heatingCoil.OutletAirTemp, heatingCoil.OutletAirHumRat);

QCoilActual = HeatingCoilLoad;
if (std::abs(heatingCoil.NominalCapacity) < 1.e-8) {
if (heatingCoil.AirLoopNum > 0) {
state.dataAirLoop->AirLoopAFNInfo(heatingCoil.AirLoopNum).AFNLoopHeatingCoilMaxRTF =
max(state.dataAirLoop->AirLoopAFNInfo(heatingCoil.AirLoopNum).AFNLoopHeatingCoilMaxRTF, 0.0);
}
} else {
if (heatingCoil.AirLoopNum > 0) {
state.dataAirLoop->AirLoopAFNInfo(heatingCoil.AirLoopNum).AFNLoopHeatingCoilMaxRTF =
max(state.dataAirLoop->AirLoopAFNInfo(heatingCoil.AirLoopNum).AFNLoopHeatingCoilMaxRTF,
HeatingCoilLoad / heatingCoil.NominalCapacity);
}
}
Comment on lines -1897 to -1908
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@mitchute mitchute May 5, 2026

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It's great that you were able to strip away so much and keep the same behavior.


// set outlet node temp so parent objects can call calc directly without have to simulate entire model
state.dataLoopNodes->Node(heatingCoil.AirOutletNodeNum).Temp = heatingCoil.OutletAirTemp;
Expand Down Expand Up @@ -2275,10 +2263,6 @@ namespace HeatingCoils {
heatingCoil.OutletAirEnthalpy = Psychrometrics::PsyHFnTdbW(heatingCoil.OutletAirTemp, heatingCoil.OutletAirHumRat);

QCoilActual = HeatingCoilLoad;
if (heatingCoil.AirLoopNum > 0) {
state.dataAirLoop->AirLoopAFNInfo(heatingCoil.AirLoopNum).AFNLoopHeatingCoilMaxRTF =
max(state.dataAirLoop->AirLoopAFNInfo(heatingCoil.AirLoopNum).AFNLoopHeatingCoilMaxRTF, heatingCoil.RTF);
}
state.dataHVACGlobal->ElecHeatingCoilPower = heatingCoil.ElecUseLoad;

// set outlet node temp so parent objects can call calc directly without have to simulate entire model
Expand Down
51 changes: 0 additions & 51 deletions src/EnergyPlus/UnitarySystem.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -12725,13 +12725,6 @@ namespace UnitarySystems {
int InletNode = this->CoolCoilInletNodeNum;
Real64 DesOutTemp = this->m_DesiredOutletTemp;
Real64 DesOutHumRat = this->m_DesiredOutletHumRat;
Real64 LoopDXCoilMaxRTFSave = 0.0;
if (state.afn->distribution_simulated && this->m_sysType != SysType::PackagedAC && this->m_sysType != SysType::PackagedHP &&
this->m_sysType != SysType::PackagedWSHP) {
LoopDXCoilMaxRTFSave = state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopDXCoilRTF;
state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopDXCoilRTF = 0.0;
}

std::string CompName = this->m_CoolingCoilName;
HVAC::FanOp fanOp = this->m_FanOpMode;
Real64 SpeedRatio = 0.0;
Expand Down Expand Up @@ -14531,12 +14524,6 @@ namespace UnitarySystems {
this->m_CoolingCycRatio = CycRatio;
this->m_DehumidificationMode = DehumidMode;

if (state.afn->distribution_simulated && this->m_sysType != SysType::PackagedAC && this->m_sysType != SysType::PackagedHP &&
this->m_sysType != SysType::PackagedWSHP) {
state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopDXCoilRTF =
max(state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopDXCoilRTF, LoopDXCoilMaxRTFSave);
}

if (this->m_coolCoilType == HVAC::CoilType::CoolingWater || this->m_coolCoilType == HVAC::CoilType::CoolingWaterDetailed) {
mdot = PartLoadFrac * this->MaxCoolCoilFluidFlow;
PlantUtilities::SetComponentFlowRate(state, mdot, this->CoolCoilFluidInletNode, this->CoolCoilFluidOutletNodeNum, this->CoolCoilPlantLoc);
Expand Down Expand Up @@ -14584,17 +14571,6 @@ namespace UnitarySystems {
int CompIndex = this->m_HeatingCoilIndex;
HVAC::FanOp fanOp = this->m_FanOpMode;
Real64 DesOutTemp = this->m_DesiredOutletTemp;

Real64 LoopHeatingCoilMaxRTFSave = 0.0;
Real64 LoopDXCoilMaxRTFSave = 0.0;
if (state.afn->distribution_simulated && this->m_sysType != SysType::PackagedAC && this->m_sysType != SysType::PackagedHP &&
this->m_sysType != SysType::PackagedWSHP) {
LoopHeatingCoilMaxRTFSave = state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF;
state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF = 0.0;
LoopDXCoilMaxRTFSave = state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopDXCoilRTF;
state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopDXCoilRTF = 0.0;
}

Real64 PartLoadFrac = 0.0;
Real64 SpeedRatio = 0.0;
Real64 CycRatio = 0.0;
Expand Down Expand Up @@ -15222,14 +15198,6 @@ namespace UnitarySystems {
this->m_HeatingCycRatio = CycRatio;
HeatCoilLoad = ReqOutput;

if (state.afn->distribution_simulated && this->m_sysType != SysType::PackagedAC && this->m_sysType != SysType::PackagedHP &&
this->m_sysType != SysType::PackagedWSHP) {
state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF =
max(state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopHeatingCoilMaxRTF, LoopHeatingCoilMaxRTFSave);
state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopDXCoilRTF =
max(state.dataAirLoop->AirLoopAFNInfo(AirLoopNum).AFNLoopDXCoilRTF, LoopDXCoilMaxRTFSave);
}

if (this->m_heatCoilType == HVAC::CoilType::HeatingWater || this->m_heatCoilType == HVAC::CoilType::HeatingSteam) {
mdot = PartLoadFrac * this->MaxHeatCoilFluidFlow;
PlantUtilities::SetComponentFlowRate(state, mdot, this->HeatCoilFluidInletNode, this->HeatCoilFluidOutletNodeNum, this->HeatCoilPlantLoc);
Expand Down Expand Up @@ -15272,17 +15240,6 @@ namespace UnitarySystems {
Real64 DesOutTemp = this->m_DesiredOutletTemp;
std::string_view CompName = this->m_SuppHeatCoilName;

Real64 LoopHeatingCoilMaxRTFSave = 0.0;
Real64 LoopDXCoilMaxRTFSave = 0.0;
if (state.afn->distribution_simulated && this->m_sysType != SysType::PackagedAC && this->m_sysType != SysType::PackagedHP &&
this->m_sysType != SysType::PackagedWSHP) {
auto &afnInfo = state.dataAirLoop->AirLoopAFNInfo(AirLoopNum);
LoopHeatingCoilMaxRTFSave = afnInfo.AFNLoopHeatingCoilMaxRTF;
afnInfo.AFNLoopHeatingCoilMaxRTF = 0.0;
LoopDXCoilMaxRTFSave = afnInfo.AFNLoopDXCoilRTF;
afnInfo.AFNLoopDXCoilRTF = 0.0;
}

// IF there is a fault of coil SAT Sensor
if (this->m_FaultyCoilSATFlag) {
// calculate the sensor offset using fault information
Expand Down Expand Up @@ -15635,14 +15592,6 @@ namespace UnitarySystems {
} // IF (NOT EMS OVERRIDE) THEN

} // IF SENSIBLE LOAD
} // IF((GetCurrentScheduleValue(state, UnitarySystem(UnitarySysNum)%m_SysAvailSchedPtr) > 0.0d0) .AND. &

// LoopHeatingCoilMaxRTF used for AirflowNetwork gets set in child components (gas and fuel)
if (state.afn->distribution_simulated && this->m_sysType != SysType::PackagedAC && this->m_sysType != SysType::PackagedHP &&
this->m_sysType != SysType::PackagedWSHP) {
auto &afnInfo = state.dataAirLoop->AirLoopAFNInfo(AirLoopNum);
afnInfo.AFNLoopHeatingCoilMaxRTF = max(afnInfo.AFNLoopHeatingCoilMaxRTF, LoopHeatingCoilMaxRTFSave);
afnInfo.AFNLoopDXCoilRTF = max(afnInfo.AFNLoopDXCoilRTF, LoopDXCoilMaxRTFSave);
}

if (this->m_suppHeatCoilType == HVAC::CoilType::HeatingWater || this->m_suppHeatCoilType == HVAC::CoilType::HeatingSteam) {
Expand Down
4 changes: 0 additions & 4 deletions src/EnergyPlus/VariableSpeedCoils.cc
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Expand Up @@ -199,10 +199,6 @@ namespace VariableSpeedCoils {
// two additional output variables
varSpeedCoil.SpeedNumReport = SpeedCal;
varSpeedCoil.SpeedRatioReport = SpeedRatio;

if (varSpeedCoil.AirLoopNum > 0 && state.afn->distribution_simulated) {
state.dataAirLoop->AirLoopAFNInfo(varSpeedCoil.AirLoopNum).AFNLoopDXCoilRTF = max(varSpeedCoil.RunFracCool, varSpeedCoil.RunFracHeat);
}
}

void GetVarSpeedCoilInput(EnergyPlusData &state)
Expand Down
2 changes: 1 addition & 1 deletion tst/EnergyPlus/unit/Furnaces.unit.cc
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Expand Up @@ -1930,7 +1930,7 @@ TEST_F(EnergyPlusFixture, UnitaryHeatCool_AFN_RTF)
SimFurnace(*state, state->dataFurnaces->Furnace(1).Name, FirstHVACIteration, AirLoopNum, CompIndex);

// Check that the runtime fraction is less than one so the impact of cycling fan is correctly accounted for in the AFN
EXPECT_TRUE(state->dataAirLoop->AirLoopAFNInfo(1).AFNLoopHeatingCoilMaxRTF < 1);
EXPECT_TRUE(state->dataAirLoop->AirLoopAFNInfo(1).AFNLoopOnOffFanRTF < 1);
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@lymereJ lymereJ May 4, 2026

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Check for fan RTF instead of coil RTF.


// Check that the system heating capacity is the same as the heating coil
EXPECT_NEAR(state->dataHeatingCoils->HeatingCoil(1).NominalCapacity, state->dataFurnaces->Furnace(1).DesignHeatingCapacity, 1e-6);
Expand Down
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