Index: firmware/App/Services/Reservoirs.c
===================================================================
diff -u -rf5dc98b3d5fcd39e3ab502fbe81110e188ce0ec5 -r38974e7129adace42bc44cacbf384a0b1442046c
--- firmware/App/Services/Reservoirs.c	(.../Reservoirs.c)	(revision f5dc98b3d5fcd39e3ab502fbe81110e188ce0ec5)
+++ firmware/App/Services/Reservoirs.c	(.../Reservoirs.c)	(revision 38974e7129adace42bc44cacbf384a0b1442046c)
@@ -52,12 +52,12 @@
 #define MAX_REDUNDANT_LOAD_CELL_DIFF              50.0                                            ///< Maximum difference in redundant load cells when determining if fill completed.
 
 #define RESERVOIR_TEMPERATURE_TAU_C_PER_MIN      -0.512                                           ///< Reservoir temperature time constant C/min.
-#define ULTRAFILTER_TEMPERATURE_TAU_C_PER_MIN    -0.512                                           ///< Ultrafilter temperature time constant C/min.
+#define ULTRAFILTER_TEMPERATURE_TAU_C_PER_MIN    -4.565                                           ///< Ultrafilter temperature time constant C/min.
 #define ULTRAFILTER_VOLUME_ML                     700                                             ///< Ultrafilter volume in milliliters.
-#define RESERVOIR_EXTRA_TEMPERATURE               1.0                                             ///< Reservoirs extra margin temperature.
 
 // ********** private data **********
 
+/// Heaters temperature calculation data structure
 typedef struct
 {
     U32 timeReservoirCycleMS;                                                                     ///< Time reservoir cycle in milliseconds.
@@ -72,7 +72,7 @@
     F32 flowTargetDialysateLPM;                                                                   ///< Dialysate target flow rate in L/min.
 } HEATERS_TEMPERATURE_CALC_DATA_T;
 
-static HEATERS_TEMPERATURE_CALC_DATA_T heatersTempCalc;
+static HEATERS_TEMPERATURE_CALC_DATA_T heatersTempCalc;                                           ///< Heaters temperature calculations data structure.
 static U32 reservoirDataPublicationTimerCounter = 0;                                              ///< used to schedule reservoir data publication to CAN bus.
 
 static OVERRIDE_U32_T activeReservoir = { 0, 0, 0, 0 };                                           ///< The active reservoir that the DG is filling/draining/etc.
@@ -91,7 +91,7 @@
 static BOOL tareLoadCellRequest;                                                                  ///< Flag indicates if load cell tare has been requested by HD.
 static DG_RESERVOIR_VOLUME_RECORD_T reservoirsCalRecord;                                          ///< DG reservoirs non-volatile record.
 static F32 targetFillFlowRateLPM;                                                                 ///< Target fill flow rate in L/min.
-static BOOL isThisTheFirstCycle = TRUE;
+static BOOL isThisTheFirstCycle = TRUE;                                                           ///< Boolean flag to indicate whether this is the first cycle.
 
 /// Conversion of ultrafilter tau in C/min to C/ms.
 static const F32 ULTRAFILTER_TAU_C_PER_MS = ULTRAFILTER_TEMPERATURE_TAU_C_PER_MIN / ( SEC_PER_MIN * MS_PER_SECOND );
@@ -346,7 +346,6 @@
     // stop fill command only valid in fill mode
     if ( DG_MODE_FILL == getCurrentOperationMode() )
     {
-        fillVolumeTargetMl.data = 0;
         requestNewOperationMode( DG_MODE_GENE );
         cmdResponse.rejected = FALSE;
     }
@@ -613,18 +612,26 @@
     F32 UFTimeConstant  = 0.0;
     F32 tempLastFill    = getLastFillTemperature();
 
-    F32 tempReservoirUse                 = heatersTempCalc.tempTargetTrimmer + RESERVOIR_EXTRA_TEMPERATURE;
-    heatersTempCalc.tempReservoirEndFill = tempReservoirUse - ( heatersTempCalc.timeReservoirFill2SwitchMS * RESERVOIR_TAU_C_PER_MS );
-    heatersTempCalc.tempReservoir0       = heatersTempCalc.tempReservoirEndFill - ( ( heatersTempCalc.timeReservoirFillMS * 0.5 ) * RESERVOIR_TAU_C_PER_MS );
+    if ( FALSE == isThisTheFirstFill() )
+    {
+        F32 tempReservoirUse                 = heatersTempCalc.tempTargetTrimmer + RESERVOIR_EXTRA_TEMPERATURE;
+        heatersTempCalc.tempReservoirEndFill = tempReservoirUse - ( heatersTempCalc.timeReservoirFill2SwitchMS * RESERVOIR_TAU_C_PER_MS );
+        heatersTempCalc.tempReservoir0       = heatersTempCalc.tempReservoirEndFill - ( ( heatersTempCalc.timeReservoirFillMS * 0.5 ) * RESERVOIR_TAU_C_PER_MS );
 
-    heatersTempCalc.timeUFDecayMS        = (F32)heatersTempCalc.timeReservoirCycleMS - heatersTempCalc.timeReservoirFillMS;
-    UFTimeConstant                       = heatersTempCalc.timeUFDecayMS * ULTRAFILTER_TAU_C_PER_MS;
-    heatersTempCalc.tempUFFill           = tempLastFill + UFTimeConstant;
+        heatersTempCalc.timeUFDecayMS        = (F32)heatersTempCalc.timeReservoirCycleMS - heatersTempCalc.timeReservoirFillMS;
+        UFTimeConstant                       = heatersTempCalc.timeUFDecayMS * ULTRAFILTER_TAU_C_PER_MS;
+        heatersTempCalc.tempUFFill           = tempLastFill + UFTimeConstant;
 
-    F32 tempTargetNumerator              = heatersTempCalc.tempReservoir0 - ( ( ULTRAFILTER_VOLUME_ML / targetFillVolML ) * heatersTempCalc.tempUFFill );
-    F32 targetTempDenominator            = ( ( targetFillVolML - ULTRAFILTER_VOLUME_ML ) / targetFillVolML );
-    tempTarget                           = tempTargetNumerator / targetTempDenominator;
+        F32 tempTargetNumerator              = heatersTempCalc.tempReservoir0 - ( ( ULTRAFILTER_VOLUME_ML / targetFillVolML ) * heatersTempCalc.tempUFFill );
+        F32 targetTempDenominator            = ( ( targetFillVolML - ULTRAFILTER_VOLUME_ML ) / targetFillVolML );
+        tempTarget                           = tempTargetNumerator / targetTempDenominator;
+    }
+    else
+    {
+        tempTarget                           = heatersTempCalc.tempTargetTrimmer + RESERVOIR_EXTRA_TEMPERATURE;
+    }
 
+
     return tempTarget;
 }