Followup on the assertion failure solving Te at low load condition in VRFFluidTCtrl model

src/EnergyPlus/HVACVariableRefrigerantFlow.cc

@@ -13965,10 +13965,27 @@ void VRFCondenserEquipment::VRFOU_CalcCompC(EnergyPlusData &state,
                     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 = 6 + TeTol; // MinOutdoorUnitTe; //SmallLoadTe( Te'_new ) is constant during iterations
+                        SmallLoadTe = MinOutdoorUnitTe + TeTol; // MinOutdoorUnitTe; //SmallLoadTe( Te'_new ) is constant during iterations
                     } 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

src/EnergyPlus/HVACVariableRefrigerantFlow.hh

@@ -315,6 +315,8 @@ 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
         // The following are for the Algorithm Type: VRF model based on physics, applicable for Fluid Temperature Control
         int AlgorithmIUCtrl;             // VRF indoor unit contrl algorithm, 1-High sensible, 2-Te/Tc constant
         Array1D<Real64> CompressorSpeed; // compressor speed array [rps]

tst/EnergyPlus/unit/HVACVariableRefrigerantFlow.unit.cc

@@ -13363,7 +13363,7 @@ 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(0.4619, state->dataHVACVarRefFlow->VRF(1).VRFCondCyclingRatio, 0.0001);
+    EXPECT_NEAR(0.4772, 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);