Index: firmware/App/Controllers/BalancingChamber.c
===================================================================
diff -u -r2582d728ac1be6d159fa0ef37b1d443f09d7a168 -r8e93a6e39b2c7af5f0b47ef1272a2b53446fab0b
--- firmware/App/Controllers/BalancingChamber.c	(.../BalancingChamber.c)	(revision 2582d728ac1be6d159fa0ef37b1d443f09d7a168)
+++ firmware/App/Controllers/BalancingChamber.c	(.../BalancingChamber.c)	(revision 8e93a6e39b2c7af5f0b47ef1272a2b53446fab0b)
@@ -46,6 +46,7 @@
 #define SPENT_DIFF_COUNT_ZERO                       0                                           ///< Zero count difference for spent side fill comparing target count
 #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)
 
 /// Payload record structure for balancing chamber switch only request
 typedef struct
@@ -1189,6 +1190,10 @@
     U32 absDiffSpentFillCount       = 0;
     U32 adjustedSpeed               = 0;
     U32 spentDialPumpSpeed          = getD48PumpSpeedForBCFill();
+    U32 initialD48PumpSpeed         = calculateD48PumpSpeedForBCFill();
+    U32 minD48Speed                 = initialD48PumpSpeed - ( initialD48PumpSpeed * D48_SPEED_RANGE_LIMIT );
+    U32 maxD48Speed                 = initialD48PumpSpeed + ( initialD48PumpSpeed * D48_SPEED_RANGE_LIMIT );
+    U32 d48SpeedPostRangeCheck      = 0;
 
     // Collect the next sample of spent pressure
     lastPrevSpentDialPressure   = prevSpentDialPressure;
@@ -1217,8 +1222,10 @@
                 spentDialPumpSpeed -= adjustedSpeed;
             }
 
+            d48SpeedPostRangeCheck = RANGE( spentDialPumpSpeed, minD48Speed, maxD48Speed );
+
             // Update the D48 pump speed
-            setD48PumpSpeedForBCFill( spentDialPumpSpeed );
+            setD48PumpSpeedForBCFill( d48SpeedPostRangeCheck );
         }
 
         //Update spent fill is complete