Index: firmware/App/Controllers/Heaters.c
===================================================================
diff -u -rff0edadf0c6f161a0a092ddaf94d1940d64f7d5e -r4f85c7f9ea610584566e869723874bbeffd6b41e
--- firmware/App/Controllers/Heaters.c	(.../Heaters.c)	(revision ff0edadf0c6f161a0a092ddaf94d1940d64f7d5e)
+++ firmware/App/Controllers/Heaters.c	(.../Heaters.c)	(revision 4f85c7f9ea610584566e869723874bbeffd6b41e)
@@ -45,10 +45,15 @@
 // ********** private definitions **********
 
 #define AC_HEATER_TX_MAX_DUTY_CYCLE                                0.50F                                                           ///< AC Heater treatment mode max duty cycle (50% of 1400W : 700W )
-#define AC_HEATER_HEAT_MAX_DUTY_CYCLE                              0.70F                                                           ///< AC Heater heat disinfect mode max duty cycle (70% of 1400W : 980W )
+#define AC_HEATER_LOW_HEAT_MAX_DUTY_CYCLE                          0.70F                                                           ///< AC Heater heat disinfect mode max duty cycle (70% of 1400W : 980W )
+#define AC_HEATER_UPPER_HEAT_MAX_DUTY_CYCLE                        0.50F                                                           ///< AC Heater heat disinfect mode reduced duty cycle (50% of 1400W : 700W )
+#define AC_HEATER_REDUCED_DUTY_CYCLE                               0.40F                                                           ///< AC Heater heat disinfect mode reduced duty cycle (40% of 1400W : 700W )
 #define AC_HEATER_MAX_DUTY_CYCLE                                   1.0F                                                            ///< AC Heater max duty cycle (100.0%) or ON state
 #define DC_HEATER_MAX_DUTY_CYCLE                                   1.0F                                                            ///< DC Heater max duty cycle (100%) or ON state
 #define HEATERS_MIN_DUTY_CYCLE                                     0.0F                                                            ///< Heaters minimum duty cycle (0.00%) or OFF state
+#define HEATERS_DISINFECT_TEMPERATURE_VERY_HIGH_DRIFT_C            10.0F                                                           ///< Heaters disinfect temperature very high drift in C.
+#define HEATERS_DISINFECT_TEMPERATURE_HIGH_DRIFT_C                 7.0F                                                            ///< Heaters disinfect temperature high drift in C.
+#define HEATERS_DISINFECT_TEMPERATURE_MED_DRIFT_C                  5.0F                                                            ///< Heaters disinfect temperature medium drift in C.
 #define HEATERS_DISINFECT_TEMPERATURE_DRIFT_C                      3.0F                                                            ///< Heaters disinfect temperature drift in C.
 #define HEATERS_ZERO_DELTA_TEMP_C                                  0.0F                                                            ///< Heaters zero delta temperature in C.
 #define HEATERS_DUTY_CYCLE_CONVERSION_FACTOR                       100.0F                                                          ///< Heaters duty cycle 0: OFF, 100: 100% duty cycle.
@@ -983,6 +988,8 @@
         else
         {
             // TODO : Calculate required duty cycle
+            // Start Open loop control with max power for heating
+            control[ heater ].data = AC_HEATER_LOW_HEAT_MAX_DUTY_CYCLE;
             state = HEATER_EXEC_STATE_CONTROL_TO_DISINFECT_TARGET;
         }
     }
@@ -1156,11 +1163,38 @@
 {
     HEATERS_STATE_T state  = HEATER_EXEC_STATE_CONTROL_TO_DISINFECT_TARGET;
 
-    //TODO : update dutycycle for the heat disinfect state
+    if ( D5_HEAT == heater )
+    {
+        F32 currentTemperature = getFilteredTemperatureValue( D78_TEMP );
+        F32 heaterTemperature = getFilteredTemperatureValue( D4_TEMP );
+        F32 targetTemperature  = getHeaterTargetTemperature( heater );
+        F32 deltaTemp = currentTemperature - targetTemperature;
 
-    setHeaterControl( D45_HEAT );
-    setHeaterControl( D5_HEAT );
+        if ( heaterTemperature > HEATER_TARGET_TEMPERATURE_MAX )
+        {
+            control[ D5_HEAT ].data = HEATERS_MIN_DUTY_CYCLE;
+        }
+        else if ( deltaTemp > HEATERS_DISINFECT_TEMPERATURE_VERY_HIGH_DRIFT_C )
+        {
+            control[ D5_HEAT ].data = HEATERS_MIN_DUTY_CYCLE;
+        }
+        else if ( currentTemperature < targetTemperature )
+        {
+            control[ D5_HEAT ].data = AC_HEATER_LOW_HEAT_MAX_DUTY_CYCLE;
+        }
+        else if ( deltaTemp > HEATERS_DISINFECT_TEMPERATURE_HIGH_DRIFT_C )
+        {
+            control[ D5_HEAT ].data = AC_HEATER_REDUCED_DUTY_CYCLE;
+        }
+        // TODO : if the current temp goes beyond the set limit + threshold, reduce the PWM Cycle
+        else if ( deltaTemp >  HEATERS_DISINFECT_TEMPERATURE_DRIFT_C )
+        {
+            control[ D5_HEAT ].data = AC_HEATER_UPPER_HEAT_MAX_DUTY_CYCLE;
+        }
 
+        setHeaterControl( D5_HEAT );
+    }
+
     return state;
 }