From 62fd1a45bc619ecd9260d9ce56f27459b2793d11 Mon Sep 17 00:00:00 2001
From: rraustad <rraustad@fsec.ucf.edu>
Date: Tue, 24 Dec 2024 19:38:28 -0500
Subject: [PATCH] expm1

---
 src/EnergyPlus/WaterToAirHeatPumpSimple.cc | 2 +-
 src/EnergyPlus/WaterUse.cc                 | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/EnergyPlus/WaterToAirHeatPumpSimple.cc b/src/EnergyPlus/WaterToAirHeatPumpSimple.cc
index a236032ff54..45c830aef69 100644
--- a/src/EnergyPlus/WaterToAirHeatPumpSimple.cc
+++ b/src/EnergyPlus/WaterToAirHeatPumpSimple.cc
@@ -3768,7 +3768,7 @@ namespace WaterToAirHeatPumpSimple {
         To1 = aa + LatentCapacityTimeConstant;
         Error = 1.0;
         while (Error > 0.001) {
-            To2 = aa - LatentCapacityTimeConstant * (std::exp(-To1 / LatentCapacityTimeConstant) - 1.0);
+            To2 = aa - LatentCapacityTimeConstant * std::expm1(-To1 / LatentCapacityTimeConstant);
             Error = std::abs((To2 - To1) / To1);
             To1 = To2;
         }
diff --git a/src/EnergyPlus/WaterUse.cc b/src/EnergyPlus/WaterUse.cc
index 41e4a92d20f..76f3fcc5aeb 100644
--- a/src/EnergyPlus/WaterUse.cc
+++ b/src/EnergyPlus/WaterUse.cc
@@ -1497,7 +1497,7 @@ namespace WaterUse {
             case HeatRecovHX::CrossFlow: { // Unmixed
                 Real64 CapacityRatio = MinCapacityRate / max(DrainCapacityRate, HXCapacityRate);
                 Real64 NTU = this->HXUA / MinCapacityRate;
-                this->Effectiveness = 1.0 - std::exp((std::pow(NTU, 0.22) / CapacityRatio) * (std::exp(-CapacityRatio * std::pow(NTU, 0.78)) - 1.0));
+                this->Effectiveness = 1.0 - std::exp((std::pow(NTU, 0.22) / CapacityRatio) * std::expm1(-CapacityRatio * std::pow(NTU, 0.78)));
             } break;
             default:
                 break;