Indoor Heating Unit - The solution to overheating

Indoor Heating Unit - The solution to overheating

Resolving Overheating

When an NRG control displays "HEAT ON" but the heater does not fire up, it indicates the heater has overheated and tripped out on high limit. 

Common Causes of Overheating:

1.  Loss of Power During Operation:

  • This can be due to a power cut or turning off the heater from its local isolator. 

2.  Lack of Ventilation:

  • New installations: Follow regulations and manufacturer's instructions for ventilation requirements. 
  • Existing Installations: Ensure the area around the heater is not obstructed (e.g., no pallets, boxes, or racking that can cause overheating) 
  • Maintenance: Blocked bents can reduce ventilation. Regularly check and maintain vents. 
  • Ductwork: Ensue ductwork is of suitable size and meets heater requirements. Check for activted fire dampers and clocked ainlet air filters. 

3.  Incorrect Burner Pressure:

  • Over firing due to incorrect burner pressure should not occur if the heater is correctly commissioned and serviced by a correctly qualified Gas Safe engineer

4.  Stratification:

  • Warm air trapped in the roof void re-circulates through the heater, causing overheating. This is common in higher-level installations.

5.  Distribution Fan Failure:

  • The heat exchanger needs airflow to stay cool. Ensure the distribution fan is functioning correctly. 

Resetting Overheat Function:

All warm air heaters have an overheat reset function, located inside or outside the heater depending on its age.  Follow safety precautions, such as turning off the power supply before attempting any internal reset. 

Reset Procedure for:

CTU, CTUC, ELU unit heaters:

  • The overheat reset button is located internally.

MGB, MOB, ELG, ELO cabinet heaters:

  • The overheat reset button is located externally at the bottom of the front panel of the heater.

The limit thermostat pretects the heater from overheating due to reduced airflow over the heat exchanger. it is a manual reset device that prevents the heater from restarting until reset.

After resetting, identify and resolve the problem that caused the limit thermostat to activate.

IMPORTANT NOTE:

Pressing the reset button on oil-fired and LPG-fired cabinet heater can build up unburnt fuel in the heat exchanger. If in doubt contact your usual gas safe engineer or the Combat Technical Help Team.

Should you require additional assistance please contact our Technical Help Team on 0121 506 7700 option 3 or email us at [email protected]

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