diff --git a/src/CNRECS.DEF b/src/CNRECS.DEF
index 7a9543975..ef5415773 100644
--- a/src/CNRECS.DEF
+++ b/src/CNRECS.DEF
@@ -4116,6 +4116,10 @@ RECORD DHWSYSRES_IVL "DHWSYSRES interval sub" *SUBSTRUCT  // interval substruct
 RECORD DHWSYSRES "DHWSYSRES" *RAT 	// DHWSYSRES: interval results for DHWSYS
 
 	*declare "RC wsr_Init( IVLCH ivl=-1);"
+    *declare "const DHWSYS* wsr_GetDHWSYS() const;"
+    *declare "bool wsr_IsSumOf() const { return ss == b->n; }"
+    *declare "enum WSRCHK { wsrchkCHILD=1, wsrchkSUMOF, wsrchkLOOSE, wsrchkTIGHT };"
+    *declare "WSRCHK wsr_BalChkCase() const;"
 #if 0
 	*declare "void wsr_Accum( IVLCH ivl, int firstflg);"
 #endif
diff --git a/src/cgenbal.cpp b/src/cgenbal.cpp
index 2f8443a4a..1309cda62 100644
--- a/src/cgenbal.cpp
+++ b/src/cgenbal.cpp
@@ -76,23 +76,39 @@ void cgenbal(		// Check energy balances; issue warning message if out of toleran
 	//   Known causes:
 	//      1) instantaneous DHWHEATER load carry-forward
 	//      2) HPWH internal balance errors (?)
+
 	if (ivl <= C_IVLCH_H)	// if hour or longer
 	{
-		float tolDHWSYS{ 0.01f };
-		float absTolDHWSYS{ 20.f };
-		if (ivl == C_IVLCH_H)
-		{	// short-interval errors common, use sloppy tolerences
-			tolDHWSYS = 0.10;
-			absTolDHWSYS = 100.f;
-		}
-		DHWSYSRES* pWS;
-		RLUP(WsResR, pWS)
+		static constexpr float fTol[] = { 0.01f, 0.10f };
+		static constexpr float absTol[] = { 20.f, 100.f };
+	
+		int checkCount = 0;		// count of checks performed
+		int iTol{ 0 };			// tolerance idx 0=tight, 1=loose
+								//   prior iteration needed for SUMOF
+		DHWSYSRES* pWSR;
+		RLUP(WsResR, pWSR)
 		{
-			const DHWSYSRES_IVL* pWSL = &pWS->Y + ivl - 1;
+			// eyeball current situation -- avoid duplicate and spurious msgs
+			DHWSYSRES::WSRCHK balChkCase = pWSR->wsr_BalChkCase();
+			if (balChkCase == DHWSYSRES::wsrchkCHILD
+				|| (balChkCase == DHWSYSRES::wsrchkSUMOF && checkCount <= 1))
+				continue;	// no check if child (no DHWHEATER, check not meaningful)
+			                // no check if sum_of with single source (sum_of record identical to source)
+
+			++checkCount;
+
+			// iTol: 0=tight, 1=loose
+			//   loose for PreRun and C_IVLCH_H (bigger errors common)
+			//   tight for Simulate and daily/month/year
+			//   use prior value for SUMOF
+			if (balChkCase != DHWSYSRES::wsrchkSUMOF)
+				iTol = balChkCase == DHWSYSRES::wsrchkLOOSE || ivl == C_IVLCH_H;
+
+			const DHWSYSRES_IVL* pWSL = &pWSR->Y + ivl - 1;
 			double wsTot = pWSL->wsr_SumAbs();
 			double wsNet = pWSL->qBal;
-			cgecheck(wsNet, wsTot, tolDHWSYS, absTolDHWSYS, "DHWSYS '%s'", pWS->Name(), ivl,
-					pWS->wsr_ebErrCount);
+			cgecheck(wsNet, wsTot, fTol[ iTol], absTol[ iTol], "DHWSYS '%s'", pWSR->Name(), ivl,
+					pWSR->wsr_ebErrCount);
 		}
 	}
 #endif	// SUPPRESS_ENBAL_CHECKS
diff --git a/src/dhwcalc.cpp b/src/dhwcalc.cpp
index 76db87c95..60f9cdc49 100644
--- a/src/dhwcalc.cpp
+++ b/src/dhwcalc.cpp
@@ -2454,6 +2454,31 @@ RC DHWSYSRES::wsr_Init(		// init (set to 0)
 	return rc;
 }		// DHWSYSRES::wsr_Init
 //-----------------------------------------------------------------------------
+const DHWSYS* DHWSYSRES::wsr_GetDHWSYS() const
+{	return WsR.GetAtSafe(ss);
+}	// DHWSYSRES::wsr_GetDHWSYS
+//-----------------------------------------------------------------------------
+DHWSYSRES::WSRCHK DHWSYSRES::wsr_BalChkCase()	const	// how to balance check this DHWSYSRES
+// returns wsrchkSUMOF: sum-of record, special case
+//         wsrchkCHILD: child DHWSYS (no heater), no check
+//         wsrchkLOOSE: pre-run underway, use loose tolerance
+//         wsrchkTIGHT: simulation underway, use tight tolerance
+
+{
+	WSRCHK ret{ wsrchkTIGHT };
+	const DHWSYS* pWS = wsr_GetDHWSYS();
+	if (!pWS)
+	{
+		assert(wsr_IsSumOf());
+		ret = wsrchkSUMOF;
+	}
+	else if (pWS->ws_HasCentralDHWSYS())
+		ret = wsrchkCHILD;
+	else if (pWS->ws_calcMode!=C_WSCALCMODECH_SIM)
+		ret = wsrchkLOOSE;
+	return ret;
+}		// wsr_BalChkCase
+//-----------------------------------------------------------------------------
 #if 0
 void DHWSYSRES::wsr_Accum(
 	IVLCH ivl,		// destination interval: hour/day/month/year.
@@ -3875,7 +3900,7 @@ RC HPWHLINK::hw_DoSubhrTick(		// calcs for 1 tick
 #else
 				WStr s("mon,day,hr,");
 				s += csvGen.cg_Hdgs(dumpUx);
-				// hw_pHPWH->WriteCSVHeading(hw_pFCSV, s.c_str(), nTCouples, hpwhOptions);
+				hw_pHPWH->writeCSVHeading(*hw_pFCSV, s.c_str(), nTCouples, hpwhOptions);
 #endif
 			}
 		}
@@ -3887,7 +3912,7 @@ RC HPWHLINK::hw_DoSubhrTick(		// calcs for 1 tick
 			WStr s = strtprintf("%d,%d,%d,",
 				Top.tp_date.month, Top.tp_date.mday, Top.iHr + 1);
 			s += csvGen.cg_Values(dumpUx);
-			//hw_pHPWH->WriteCSVRow(*hw_pFCSV, s.c_str(), nTCouples, hpwhOptions);
+			hw_pHPWH->writeCSVRow(*hw_pFCSV, s.c_str(), nTCouples, hpwhOptions);
 #endif
 		}
 	}
diff --git a/vendor/HPWHsim b/vendor/HPWHsim
index dd09e5aac..e4c8d6895 160000
--- a/vendor/HPWHsim
+++ b/vendor/HPWHsim
@@ -1 +1 @@
-Subproject commit dd09e5aac7109788f67cb363785268675e4ea478
+Subproject commit e4c8d6895e50ca4444a8e55a05bbf19b40b55b90