Has Your Outdoor Boiler Overheated? How To Avoid Permanent Damage

If your outdoor boiler has overheated, you may have a problem that will permanently damage your boiler. This must be addressed immediately!  

We recommend that you evaluate the possible causes (listed below) and the corresponding solutions (also listed below) so that you can take the necessary steps to PROTECT your outdoor boiler from permanent damage.


  • High Limit Switch needed to be reset. Why?
  • Boiler overheated
  • Water temp is over 190, in some cases over 210.
  • Water/steam boiled out vent tube
  • High limit switch tripped
  • No power to light and blower fan
  • Water level dropped (boiled out)
Possible Causes: Solutions:
Door left open An unlimited supply of air to the firebox is bad - it will lead to uncontrolled burning of wood fuel in the firebox that will damage the firebox steel. Please never leave the furnace firebox door open for extended periods of time. The door should only be open for brief moments to add wood fuel to the firebox and remove ash.
Pump failure Remove silver button on face of pump while pump is in operation to verify impeller shaft is spinning. If not, replace pump. See article on how to diagnose pump failure by clicking on this link HERE. For replacement pump special, call (231) 861-8200.
High limit switch cannot be reset Must wait until water temp drops below approx. 150 degrees to reset. Also, High Limit Switches have only a limited number of trips in their lifespan. This depends upon how hot and how many times the furnace high temps. A very high temp situation may kill the switch in one trip. Or it may last 12+ trips. Always have a spare on hand. Click HERE for more info on High Limit Switches.