Index: firmware/App/Controllers/BalancingChamber.c
===================================================================
diff -u -red96c724f65f6763233b2c427456b6efd19717e6 -rcceb0bf86fc6ddb1131701844960f59d968988c5
--- firmware/App/Controllers/BalancingChamber.c	(.../BalancingChamber.c)	(revision ed96c724f65f6763233b2c427456b6efd19717e6)
+++ firmware/App/Controllers/BalancingChamber.c	(.../BalancingChamber.c)	(revision cceb0bf86fc6ddb1131701844960f59d968988c5)
@@ -52,6 +52,7 @@
 #define SPENT_DIFF_COUNT_DEADBAND                   1                                           ///< Stop changing D48 pump speed when fill difference reaches close to target count
 #define D48_SPEED_ADJUST_FACTOR                     0.5F                                        ///< D48 speed adjustment factor ( 50% of speed adjustment = 0.5)
 #define D48_SPEED_RANGE_LIMIT                       0.25F                                       ///< D48 speed adjustment range check limit ( D48 speed can vary +/-25% of initial calculated speed)
+#define BAL_CHAMBER_FILL_TIMEOUT_FACTOR             1.5                                         ///< Balancing Chamber fill timeout factor (150% of observed fill count)
 
 /// Payload record structure for balancing chamber switch only request
 typedef struct
@@ -85,8 +86,9 @@
 static F32 prevSpentDialPressure;                                                               ///< Previous spent side dialysate pressure
 static F32 lastPrevSpentDialPressure;                                                           ///< Last previous spent side dialysate pressure
 static U32 currentBalChamberFillCounter;                                                        ///< Counter (in task interval) to monitor the timing spent for the spent side fill operation.
+static U32 balChamberFillTimeoutCount;                                                          ///< Timeout count (in task interval) to detect BC fill timeout.
 static S32 diffSpentFillCompleteCount;                                                          ///< Difference between spent target fill to actual fill count
-static BOOL isSpentFillComplete;
+static BOOL isSpentFillComplete;                                                                ///< Flag indicating spent side fill complete.
 
 // ********** private function prototypes **********
 
@@ -133,7 +135,7 @@
     balChamberValveClosePeriod                  = 0;
     isBalChamberFillInProgress                  = FALSE;
     currentBalChamberSwitchingCounter           = 0;
-    isPressureStabilizedDuringFill             = FALSE;
+    isPressureStabilizedDuringFill              = FALSE;
     lastTdDialysateFlowrate                     = 0.0F;
     balChamberDataPublicationTimerCounter       = 0;
     balChamberFillPressureDropCounter           = 0;
@@ -145,6 +147,7 @@
     prevSpentDialPressure                       = 0.0F;
     lastPrevSpentDialPressure                   = 0.0F;
     currentBalChamberFillCounter                = 0;
+    balChamberFillTimeoutCount                  = 0;
     diffSpentFillCompleteCount                  = 0;
     isSpentFillComplete                         = FALSE;
 }
@@ -431,6 +434,7 @@
     currentBalChamberSwitchingCounter   = 0;
     balChamberSWState                   = BAL_CHAMBER_SW_STATE1;
     currentBalChamberFillCounter        = 0;
+    balChamberFillTimeoutCount          = 0;
     isBalChamberFillInProgress          = FALSE;
     isPressureStabilizedDuringFill      = FALSE;
     isPressureDroppedDuringFill         = FALSE;
@@ -545,6 +549,12 @@
     freshDialPressure               = getFilteredPressure( D18_PRES );
     spentDialPressure               = getFilteredPressure( D51_PRES );
 
+    // If fill is taking too long, set an alarm for fill timeout
+    if ( ( balChamberFillTimeoutCount > 0 ) && ( currentBalChamberFillCounter > balChamberFillTimeoutCount ) )
+    {
+        SET_ALARM_WITH_2_U32_DATA( ALARM_ID_DD_BC_FILL_TIMEOUT_FAULT, currentBalChamberFillCounter, balChamberFillTimeoutCount );
+    }
+
     // Check fresh dialysate pressure back in range to indicate fresh fill complete.
     if ( ( freshDialPressure >= FRESH_DIAL_PRESSURE_MIN_PSIG ) && ( freshDialPressure <= FRESH_DIAL_PRESSURE_MAX_PSIG ) )
     {
@@ -561,6 +571,12 @@
     // Check both spent and fresh side fill is complete
     if ( ( TRUE == isSpentFillComplete ) && ( TRUE == isPressureStabilizedDuringFill ) || ( FALSE == isFirstCycleBCSwitchingCompleted ) )
     {
+        // On successful completion, learn timeout as 150% of the observed fill count (once per cycle).
+        if ( balChamberFillTimeoutCount == 0U )
+        {
+            balChamberFillTimeoutCount = currentBalChamberFillCounter * BAL_CHAMBER_FILL_TIMEOUT_FACTOR;
+        }
+
         // close the state 1 opened valves
         valveControlForBCState1FillEnd();
         isBalChamberFillInProgress = FALSE;
@@ -649,6 +665,7 @@
     isPressureDroppedDuringFill         = FALSE;
     balChamberSWState                   = BAL_CHAMBER_SW_STATE2;
     currentBalChamberFillCounter        = 0;
+    balChamberFillTimeoutCount          = 0;
     isSpentFillComplete                 = FALSE;
     lastPrevSpentDialPressure           = 0.0F;
     prevSpentDialPressure               = 0.0F;
@@ -717,12 +734,24 @@
         }
     }
 
+    // If fill is taking too long, set an alarm for fill timeout
+    if ( ( balChamberFillTimeoutCount > 0 ) && ( currentBalChamberFillCounter > balChamberFillTimeoutCount ) )
+    {
+        SET_ALARM_WITH_2_U32_DATA( ALARM_ID_DD_BC_FILL_TIMEOUT_FAULT, currentBalChamberFillCounter, balChamberFillTimeoutCount );
+    }
+
     // Spent side of balancing chamber fill is complete or not
     checkSpentFillComplete( spentDialPressure );
 
     // Check switching cycle time or pressure check for valve closure
     if ( ( TRUE == isSpentFillComplete ) && ( TRUE == isPressureStabilizedDuringFill ) || ( FALSE == isFirstCycleBCSwitchingCompleted ) )
     {
+        // On successful completion, learn timeout as 150% of the observed fill count (once per cycle).
+        if ( balChamberFillTimeoutCount == 0U )
+        {
+            balChamberFillTimeoutCount = currentBalChamberFillCounter * BAL_CHAMBER_FILL_TIMEOUT_FACTOR;
+        }
+
         // close the valves
         valveControlForBCState2FillEnd();
         isBalChamberFillInProgress = FALSE;