diff --git a/src/CNDTYPES.DEF b/src/CNDTYPES.DEF
index 5da8fe008..fa7c2d1e2 100644
--- a/src/CNDTYPES.DEF
+++ b/src/CNDTYPES.DEF
@@ -461,6 +461,8 @@ PIPESEGP -- "class PIPESEG*"
 			AOSMITHSHPT66 "AOSmithSHPT66"
 			AOSMITHSHPT80 "AOSmithSHPT80"
 
+			AQUATHERMAIRE "AquaThermAire"		// Villara AquaThermAire system
+
 			GENERIC1 "GenericTier1"			// Generic Tier 1
 			GENERIC2 "GenericTier2"			// Generic Tier 2
 			GENERIC3 "GenericTier3"			// Generic Tier 3
diff --git a/src/dhwcalc.cpp b/src/dhwcalc.cpp
index bccfafc54..088ba7ff4 100644
--- a/src/dhwcalc.cpp
+++ b/src/dhwcalc.cpp
@@ -3069,6 +3069,8 @@ RC HPWHLINK::hw_InitResistance(		// set up HPWH has EF-rated resistance heater
 	{ C_WHASHPTYCH_AWHSTIER3GENERIC65, hwatSMALL | HPWH::MODELS_AWHSTier3Generic65 },
 	{ C_WHASHPTYCH_AWHSTIER3GENERIC80, hwatSMALL | HPWH::MODELS_AWHSTier3Generic80 },
 
+	{ C_WHASHPTYCH_AQUATHERMAIRE, hwatSMALL | HPWH::MODELS_AQUATHERMAIRE },
+
 // large
 	{ C_WHASHPTYCH_SANCO2_GS3,      hwatLARGE | HPWH::MODELS_SANCO2_GS3_45HPA_US_SP },
 	{ C_WHASHPTYCH_COLMACCXV5_SP,   hwatLARGE | HPWH::MODELS_ColmacCxV_5_SP },
@@ -4366,8 +4368,13 @@ RC DHWHEATER::wh_Init()		// init for run
 	if (wh_IsHPWHModel())
 		rc |= wh_HPWHInit();	// set up from DHWHEATER inputs
 
-	else if (wh_type == C_WHTYPECH_INSTUEF)
-		rc |= wh_InstUEFInit();		// UEF-based instantaneous water heater model 5-2017
+	else if (wh_IsInstUEFModel())
+		rc |= wh_InstUEFInit();		// UEF-based instantaneous water heater model
+
+#if defined( _DEBUG)
+		else
+			ASSERT( 1);		// missing case
+#endif
 
 	return rc;
 }		// DHWHEATER::wh_Init
@@ -4892,7 +4899,6 @@ RC DHWHEATER::wh_DoSubhrTick(		// DHWHEATER energy use for 1 tick
 
 		if (wh_IsInstUEFModel())
 			rc |= wh_InstUEFDoSubhrTick(drawForTick, tInletMix, scaleWH, pWS->ws_tUse);
-
 		else
 		{	float deltaT = max(1.f, pWS->ws_tUse - tInletMix);
 
@@ -5222,7 +5228,6 @@ RC DHWHEATER::wh_InstUEFDoSubhrTick(
 	}
 	return rc;
 }		// DHWHEATER::wh_InstUEFDoSubhrTick
-
 //=============================================================================
 
 ///////////////////////////////////////////////////////////////////////////////
diff --git a/vendor/HPWHsim b/vendor/HPWHsim
index d20541324..92d5edf23 160000
--- a/vendor/HPWHsim
+++ b/vendor/HPWHsim
@@ -1 +1 @@
-Subproject commit d2054132479a920d651a77a733e53de2a24e634b
+Subproject commit 92d5edf2393ff8f521121484f6a62082303a8d94