diff --git a/src/dhwcalc.cpp b/src/dhwcalc.cpp
index bccfafc54..4eb3a2f71 100644
--- a/src/dhwcalc.cpp
+++ b/src/dhwcalc.cpp
@@ -3730,9 +3730,10 @@ RC HPWHLINK::hw_DoSubhrTick(		// calcs for 1 tick
 	{
 		double qTXkWh = tk.wtk_qTX / BtuperkWh;
 		hw_qTX += qTXkWh;		// subhour total (kWh)
-		double qTXPwr			// tick power per node, W
-			= qTXkWh * 1000. / (hw_nQTXNodes * Top.tp_tickDurHr);
-		hw_pNodePowerExtra_W.assign(hw_nQTXNodes, qTXPwr);
+		double qTXPwr			// tick power (W)
+			= qTXkWh * 1000. / (Top.tp_tickDurHr);
+		hw_pNodePowerExtra_W = {qTXPwr, 0., 0., 0.}; // bottom 1/4 of tank
+
 		pNPX = &hw_pNodePowerExtra_W;
 	}
 	
diff --git a/vendor/HPWHsim b/vendor/HPWHsim
index 20a682904..f9b8f7751 160000
--- a/vendor/HPWHsim
+++ b/vendor/HPWHsim
@@ -1 +1 @@
-Subproject commit 20a68290428c26c61bbde3140dd8b8fb8e366b70
+Subproject commit f9b8f77516be78a5e3f0e86ef55fec9edbcd144c