DHW instantaneous heater fixes

Author: chipbarnaby

doc/src/records/dhwmeter.md

@@ -1,9 +1,10 @@
 # DHWMETER
 
-A DHWMETER object is a user-defined "device" that records water consumption as simulated by CSE.  The data accumulated by DHWMETERs can be reported at hourly, daily, monthly, and annual (run) intervals by using REPORTs and EXPORTs of type DHWMTR.
+A DHWMETER object is a user-defined "device" that records water consumption as simulated by CSE.  The data accumulated by DHWMETERs can be reported at hourly, daily, monthly, and annual (run) intervals by using REPORTs and EXPORTs of type DHWMTR. Water use is reported in gallons.
 
-DHWMETERs account for water use in the following pre-defined end uses.  The abbreviations in parentheses are used in DHWMTR report headings.
 
+DHWMETERs account for water use in the following pre-defined end uses.  The abbreviations in parentheses are used in DHWMTR report headings.
+  
 - Total water use (Total)
 - Unknown end use (Unknown)
 - Miscellaneous draws (Faucet)

src/CNRECS.DEF

@@ -3433,8 +3433,8 @@ RECORD DHWHEATER "DHWHeater" *RAT	// input / runtime DHW heater
   *h FLOAT wh_mixDownF;			// factor for draw adjustment re HPWH setpoint > DHWSYS::ws_tUse
 								//   Some HPWHs (e.g. Sanden) have fixed (high) setpoints
 								//   draws are reduced to balance load at ws_tUse.
-  *s INt wh_drawTicks;			// duration of current draw, for HPWH and INSTUEF, ticks
-								//   allows detection of startup event
+  *s INT wh_stbyTicks;			// time since last draw, for HPWH and INSTUEF, ticks
+								//   re startup (cyclic) loss model
 
   *i TI wh_elecMtri			// meter for system electricity use (default = parent ws_elecMtri)
   *i TI wh_fuelMtri			// meter for system fuel use (default = parent ws_electMtri)

src/DHWCalc.cpp

@@ -1093,7 +1093,7 @@ RC DHWHEATER::wh_Init()		// init for run
 	wh_totOut = 0.;
 	wh_unMetHrs = 0;
 	wh_balErrCount = 0;
-	wh_drawTicks = 0;
+	wh_stbyTicks = 0;
 
 	DHWSYS* pWS = wh_GetDHWSYS();
 
@@ -1578,15 +1578,16 @@ RC DHWHEATER::wh_HPWHDoSubhr(		// HPWH subhour
 				DHWMix( pWS->ws_tUse, tOF, pWS->ws_tInlet, wh_mixDownF);
 			tHWOutF += tOF;		// note tOF may have changed (but not tO)
 			nTickNZDraw++;		// this tick has draw
-			wh_drawTicks++;		// track draw duration (info only)
+			wh_stbyTicks = 0;	// reset standby duration
 			qHW += KJ_TO_KWH(
 				     GAL_TO_L( drawForTick)
 				   * HPWH::DENSITYWATER_kgperL
 				   * HPWH::CPWATER_kJperkgC
 				   * (tO - DegFtoC( pWS->ws_tInlet)));
 		}
 		else
-			wh_drawTicks = 0;		// no draw: reset current duration
+			wh_stbyTicks++;		// no draw: accum duration
+								//   (info only)
 
 		// energy use by heat source, kWh
 		// accumulate by backup resistance [ 0] vs primary (= compressor or all resistance) [ 1]
@@ -1804,12 +1805,12 @@ RC DHWHEATER::wh_InstUEFDoSubhr(
 			}
 			else
 				nTickFullLoad += drawForTick / drawFullLoad;
-			if (!wh_drawTicks++)	// if no draw in prior tick
+			if (wh_stbyTicks)	// if no draw in prior tick
 				nTickStart++;		//   count start
 		}
 		else
 			// standby
-			wh_drawTicks = 0;	// reset draw duration
+			wh_stbyTicks++;		// reset draw duration
 	}
 
 	double tickDurHr = Top.tp_subhrTickDur / 60.;	// tick duration, hr