Index: firmware/App/Controllers/Heaters.c
===================================================================
diff -u -r0a74bcce6674271e35d5154003dd6c25011f80f9 -re803f3e6d135641015dc78e2aeac0a5489c9492c
--- firmware/App/Controllers/Heaters.c	(.../Heaters.c)	(revision 0a74bcce6674271e35d5154003dd6c25011f80f9)
+++ firmware/App/Controllers/Heaters.c	(.../Heaters.c)	(revision e803f3e6d135641015dc78e2aeac0a5489c9492c)
@@ -69,6 +69,7 @@
 #define HEATER_TEMP_CONTROL_TRANSFER                               1.0F                                                            ///< Primary Heater temperature difference to switch to control function
 #define HEATER_TARGET_TEMPERATURE_MIN                              10.0F                                                           ///< Minimum allowed target temperature for the heaters.
 #define HEATER_TARGET_TEMPERATURE_MAX                              90.0F                                                           ///< Maximum allowed target temperature for the heaters.
+#define DELTA_TEMP_ADJ_FLOW_RATE                                   150.0F                                                          ///< Fo Qd <= 150, the bottom range of second level temperature correction to be applied.
 
 #define D5_HEAT_ON_NO_FLUID_TIMEOUT_MS                             ( 10 * MS_PER_SECOND )                                          ///< Primary heater on with no flow time out in milliseconds.
 #define D45_HEAT_ON_NO_FLUID_TIMEOUT_MS                            ( 12 * MS_PER_SECOND )                                          ///< Trimmer heater on with no flow time out in milliseconds.
@@ -401,6 +402,7 @@
         F32 targetTempfromTD            = getTDTargetDialysateTemperature();
         F32 measuredTempAtDialyzer      = getConductivityTemperatureValue( D27_COND );
         F32 calcTargetTemp              = getHeaterTargetTemperature( D5_HEAT );
+        F32 dialysateFlowrate           = getTDDialysateFlowrate();
         F32 deltaTempC                  = targetTempfromTD - measuredTempAtDialyzer;
         F32 capDeltaTempC               = MIN( fabs(deltaTempC), ADJ_DELTA_TEMP_STEP );
 
@@ -421,9 +423,19 @@
         }
 
         //Make sure the adjusted temp not crossing the max and min limits.
-        adjustedPrimaryTargetTemp = MIN(adjustedPrimaryTargetTemp, ( calcTargetTemp + MAX_ADJ_DELTA_TEMP_C ) );
-        adjustedPrimaryTargetTemp = MAX(adjustedPrimaryTargetTemp, ( calcTargetTemp - MAX_ADJ_DELTA_TEMP_C ) );
+        adjustedPrimaryTargetTemp = MIN( adjustedPrimaryTargetTemp, ( calcTargetTemp + MAX_ADJ_DELTA_TEMP_C ) );
 
+        // For Qd <= 150, The bottom range of second level temperature correction not to go below the initial
+        // Delta temperature adjustment.
+        if ( dialysateFlowrate > DELTA_TEMP_ADJ_FLOW_RATE )
+        {
+            adjustedPrimaryTargetTemp = MAX( adjustedPrimaryTargetTemp, ( calcTargetTemp - MAX_ADJ_DELTA_TEMP_C ) );
+        }
+        else
+        {
+            adjustedPrimaryTargetTemp = MAX( adjustedPrimaryTargetTemp, calcTargetTemp );
+        }
+
         isTargetTempAdjusted        = TRUE;
         primaryTargetTempAdjCounter = 0;
     }