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Followup VRF warning about solveRoot of Te at small load condition #11000

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Merged
mitchute merged 15 commits into from
Jan 23, 2026
+90 −39
Merged

Followup VRF warning about solveRoot of Te at small load condition #11000

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1d3ab1c
separate warning for -1 and -2, report SmallLoadTe range in warning
Mar 20, 2025
c77f5d1
check sign of end points before solving root
Mar 20, 2025
51cb011
add back warnings, keep old upper bound SolveRoot
Mar 21, 2025
4cff147
Fix unit test
Mar 21, 2025
dc754c8
Merge remote-tracking branch 'origin/develop' into followupVRFwarning
Jul 1, 2025
7d4fa9c
fix bracket issue from merging
Jul 2, 2025
3399351
temp mod feenableexcept so apple arm can build
Jul 2, 2025
67b3cf3
Revert "temp mod feenableexcept so apple arm can build"
Jul 2, 2025
bbf4214
apply clang-format
Jul 2, 2025
821c29e
Merge remote-tracking branch 'origin/develop' into followupVRFwarning
Jul 16, 2025
7bfd8b2
Merge remote-tracking branch 'origin/develop' into followupVRFwarning
Aug 27, 2025
8940c69
Update new SolveRoot failure code, and Merge branch 'develop' of http…
rraustad Jan 21, 2026
125bd13
Remove unused and redundant code
rraustad Jan 22, 2026
964e38d
Simple comment update on cloned repo to test workflow
rraustad Jan 23, 2026
cf8ea42
Test yml update
rraustadAtTrane Jan 23, 2026
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2 changes: 1 addition & 1 deletion .github/workflows/test_pull_requests.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -277,7 +277,7 @@ jobs:
# - uses: lhotari/action-upterm@v1

- name: Fail on Regressions from Forked Repository
if: always() && matrix.run_regressions && steps.regressions.outcome == 'failure' && github.event.pull_request.head.repo.full_name != 'NREL/EnergyPlus'
if: always() && matrix.run_regressions && steps.regressions.outcome == 'failure' && github.event.pull_request.head.repo.full_name != 'NatLabRockies/EnergyPlus'
run: |
echo "::error::Regressions detected in pull request from forked repository, check job summary for details and to download regression results"
exit 1
113 changes: 79 additions & 34 deletions src/EnergyPlus/HVACVariableRefrigerantFlow.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -14206,41 +14206,86 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,
return CompResidual_FluidTCtrl(state, T_discharge_new, CondHeat, CAPFT, T_suc);
};

General::SolveRoot(state, 1.0e-3, MaxIter, SolFla, SmallLoadTe, f, MinOutdoorUnitTe,
T_suction); // SmallLoadTe is the updated Te'
if (SolFla == -1) {
// show error not converging
ShowWarningMessage(state, format("{}: low load Te adjustment failed for {}", RoutineName, this->Name));
ShowContinueErrorTimeStamp(state, "");
ShowContinueError(state, format(" Iteration limit [{}] exceeded in calculating OU evaporating temperature", MaxIter));
} else if (SolFla == -2) {
this->LowLoadTeError++;
if (LowLoadTeError < 5) {
ShowWarningMessage(state,
format("{}: no Te solution was found for {} f({})={} and f({})={} are the same sign",
RoutineName,
this->Name,
MinOutdoorUnitTe,
f(MinOutdoorUnitTe),
T_suction,
f(T_suction)));
ShowContinueErrorTimeStamp(state, "");
}
ShowRecurringWarningErrorAtEnd(state,
"Low load calculation Te solution not found as end points have the same sign",
this->LowLoadTeErrorIndex,
SolFla,
SolFla);
if (f(T_suction) < 0) {
// demand < capacity at both endpoints of the Te range, assuming f(x) is roughly monotonic than this is the low load case
// TeTol is added to prevent the final updated Te to go out of bounds
SmallLoadTe = MinOutdoorUnitTe + TeTol; // MinOutdoorUnitTe; //SmallLoadTe( Te'_new ) is constant during iterations
Real64 f_xmin = f(MinOutdoorUnitTe);
Real64 f_xmax = f(T_suction);
if (f_xmin < 0 && f_xmax < 0) {
SmallLoadTe = MinOutdoorUnitTe;
} else if (f_xmin > 0 && f_xmax > 0) {
if (f_xmin > f_xmax) {
SmallLoadTe = T_suction;
} else {
// demand > capacity at both endpoints of the Te range, take the end point x where f(x) is closer to zero
if (f(MinOutdoorUnitTe) > f(T_suction)) { // f(T_suction > 0, not equal as SolFla will not be -2
SmallLoadTe = T_suction;
} else {
SmallLoadTe = MinOutdoorUnitTe;
}
} else {
General::SolveRoot(state, 1.0e-3, MaxIter, SolFla, SmallLoadTe, f, MinOutdoorUnitTe, T_suction); // SmallLoadTe is the updated Te'
if (SolFla == -1) {
// show error not converging
if (LowLoadTeIterError == 0) {
ShowWarningMessage(state, format("{}: low load Te adjustment failed for {}", RoutineName, this->Name));
ShowContinueErrorTimeStamp(state, "");
ShowContinueError(state, format(" Iteration limit [{}] exceeded in calculating OU evaporating temperature", MaxIter));
}
ShowRecurringWarningErrorAtEnd(state,
"Low load calculation Te solution iteration limit exceeded error continues.",
this->LowLoadTeIterError,
SmallLoadTe,
SmallLoadTe);
} else if (SolFla == -2) {
if (f_xmax < 0) {
// demand < capacity at both endpoints of the Te range, assuming f(x) is roughly monotonic then this is the low load
// case TeTol is added to prevent the final updated Te to go out of bounds
SmallLoadTe = MinOutdoorUnitTe;
this->LowLoadTeError2Neg++;
if (LowLoadTeError2Neg < 5) {
ShowWarningMessage(state,
format("{}: no Te solution was found for {}, as load < capacity for the whole range of Te",
RoutineName,
this->Name));
ShowContinueErrorTimeStamp(state, "");
}
ShowRecurringWarningErrorAtEnd(
state,
"Low load calculation Te solution not found as load is smaller than min-speed capacity for the whole range",
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@mitchute mitchute Jan 23, 2026

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Maybe it's just me, but I don't understand what the warning is trying to convey. Is "Te" something you'd expect the user to understand?

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@dareumnam dareumnam Jan 23, 2026

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This warning seems more like a diagnostic message for developers, rather than a user-friendly explanation. We might consider making it more user-oriented.

this->LowLoadTeError2NegIndex,
SmallLoadTe,
SmallLoadTe);
} else {
// demand > capacity at both endpoints of the Te range, take the end point x where f(x) is closer to zero
if (f_xmin > f_xmax) { // f(T_suction > 0, not equal as SolFla would not have been -2
SmallLoadTe = T_suction;
this->LowLoadTeError2PosTsuc++;
if (LowLoadTeError2PosTsuc < 5) {
ShowWarningMessage(state,
format("{}: no Te solution was found for {}, as load > capacity for the full range of Te",
RoutineName,
this->Name));
ShowContinueErrorTimeStamp(state, "");
}
ShowRecurringWarningErrorAtEnd(
state,
"Low load calculation Te solution not found as load is larger than min-speed capacity for "
"the whole range\nTake T_suction as the updated Te",
this->LowLoadTeError2PosTsucIndex,
SmallLoadTe,
SmallLoadTe);
} else {
SmallLoadTe = MinOutdoorUnitTe;
this->LowLoadTeError2PosOUTe++;
if (LowLoadTeError2PosOUTe < 5) {
ShowWarningMessage(state,
format("{}: no Te solution was found for {}, as load > capacity for the full range of Te",
RoutineName,
this->Name));
ShowContinueErrorTimeStamp(state, "");
}
ShowRecurringWarningErrorAtEnd(
state,
"Low load calculation Te solution not found as load is larger than min-speed capacity for "
"the whole range\nTake MinOutdoorUnitTe as the updated Te",
this->LowLoadTeError2PosOUTeIndex,
SmallLoadTe,
SmallLoadTe);
}
}
}
}
Expand All @@ -14251,7 +14296,7 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,
{
// Initialization of Iteration_Te (Label11)
// i.e., find a new Te (Pipe_Te_assumed) that can generate a new T_suction equaling to SmallLoadTe.
// This requires the re-calculate of piping loss.
// This requires the re-calculation of piping loss.
NumIteTe = 1;
MaxNumIteTe = (this->EvaporatingTemp - SmallLoadTe) / 0.1 + 1; // upper bound and lower bound of Te iterations
Pipe_Te_assumed = this->EvaporatingTemp - 0.1;
Expand Down
10 changes: 8 additions & 2 deletions src/EnergyPlus/HVACVariableRefrigerantFlow.hh
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Expand Up @@ -314,8 +314,14 @@ namespace HVACVariableRefrigerantFlow {
int CoolCapFTErrorIndex = 0; // warning message index
int HeatEIRFPLRErrorIndex = 0; // warning message index
int CoolEIRFPLRErrorIndex = 0; // warning message index
int LowLoadTeError = 0;
int LowLoadTeErrorIndex = 0; // warning message index
int LowLoadTeIterError = 0;
int LowLoadTeError2Neg = 0;
int LowLoadTeError2NegIndex = 0; // warning message index
int LowLoadTeError2PosTsuc = 0;
int LowLoadTeError2PosTsucIndex = 0; // warning message index
int LowLoadTeError2PosOUTe = 0;
int LowLoadTeError2PosOUTeIndex = 0; // warning message index
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@rraustad rraustad Mar 21, 2025

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Are you planning to use these?

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@yujiex yujiex Mar 21, 2025

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yes, added back the warnings

int LowLoadTeErrorIndex = 0; // warning message index
// The following are for the Algorithm Type: VRF model based on physics, applicable for Fluid Temperature Control
int AlgorithmIUCtrl; // VRF indoor unit control algorithm, 1-High sensible, 2-Te/Tc constant
Array1D<Real64> CompressorSpeed; // compressor speed array [rps]
Expand Down
4 changes: 2 additions & 2 deletions tst/EnergyPlus/unit/HVACVariableRefrigerantFlow.unit.cc
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Expand Up @@ -2663,7 +2663,7 @@ TEST_F(EnergyPlusFixture, VRF_FluidTCtrl_VRFOU_Compressor)
thisVRF.RatedEvapCapacity * CurveValue(*state, thisVRF.OUCoolingCAPFT(1), thisVRF.CondensingTemp, thisVRF.EvaporatingTemp);
Real64 CompEvaporatingPWRSpdMin =
thisVRF.RatedCompPower * CurveValue(*state, thisVRF.OUCoolingPWRFT(1), thisVRF.CondensingTemp, thisVRF.EvaporatingTemp);
EXPECT_NEAR(0.36, CyclingRatio, 0.01);
EXPECT_NEAR(0.37, CyclingRatio, 0.01);
EXPECT_NEAR(OUEvapHeatExtract, CompEvaporatingCAPSpdMin + Ncomp, 1e-4);
EXPECT_NEAR(1500, CompSpdActual, 1);
EXPECT_NEAR(Ncomp, CompEvaporatingPWRSpdMin, 1e-4);
Expand Down Expand Up @@ -13335,7 +13335,7 @@ TEST_F(EnergyPlusFixture, VRF_FluidTCtrl_ReportOutputVerificationTest)
EXPECT_NEAR(5645.5696, thisVRFTU.TotalCoolingRate, 0.0001);
EXPECT_NEAR(84.8359, thisFan->totalPower, 0.0001);
EXPECT_NEAR(thisDXCoolingCoil.TotalCoolingEnergyRate, (thisVRFTU.TotalCoolingRate + thisFan->totalPower), 0.0001);
EXPECT_NEAR(0.4772, state->dataHVACVarRefFlow->VRF(1).VRFCondCyclingRatio, 0.0001);
EXPECT_NEAR(0.4851, state->dataHVACVarRefFlow->VRF(1).VRFCondCyclingRatio, 0.0001);
EXPECT_NEAR(state->dataHVACVarRefFlow->VRF(1).OUFanPower,
state->dataHVACVarRefFlow->VRF(1).RatedOUFanPower * state->dataHVACVarRefFlow->VRF(1).VRFCondCyclingRatio,
0.0001);
Expand Down
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