The Importance of a Heater’s High Limit Switch

High Limit Switch Installed in a Furnace

How Your Heater Works

Every heater, whether it is a gas furnace or electric heater (that uses electrified heat strips) operates in a similar fashion: heat builds up in a box and the blower motor then blows air through the box to force the heat into the living space. 

If you have a gas furnace the heat is generated in the box by a gas fire that is burned inside a heat exchanger. If you have an electric heater then heat is generated in the box by heat strips that are energized with 220-240v of electricity (much like an electric stove top). 

The blower motor, which blows air from your home through this heated box, distributing the warmer air throughout your home, keeps the box from over-heating.

Purpose of the High Limit Switch

Can you imagine what would happen if the blower stopped moving air through your heater? The box where the heat is generated would just continue to get hotter and hotter, ultimately causing a catastrophic failure in your system, which oftentimes leads to a fire in your home. 

The circulation of air through your heater is what keeps the heat from building up to a dangerous level, so if this stops, the heat can easily become dangerous. 

This is where the “high limit switch” comes into play. This tiny little switch is the safety to keep your gas furnace or electric heater from damaging itself and your home. The high limit switch has a sensor that when the heat in the box gets too high (as would be the case if the blower failed), cuts power to the heating portion of the system.  

Cutaway of a High Limit Switch

Maintenance is Key

There are many different components needed to run your blower motor and circulate the air through your heater, components like control boards, fan relays, sequencers, and the like. If any one of these many components fails, your blower will stop working and stop circulating air through your heater. The high limit switch will then turn off the heating capability, protecting the system and your home. 

This is one of the many reasons to have your system maintained twice a year. Your system may run fine and you won’t know you have a faulty high limit switch until your blower fails and nothing exists to cut off the heating capability of your system, ending in catastrophic failure. 

Testing a high limit switch is an easy process for a trained technician, and one that goes a long way to preserving your system and your home. This very small component serves a very big purpose. 

If you have any questions about your HVAC system, want to have it serviced, or get it maintained, give us a call to set up an appointment. 

If you want to learn more about what you can do to maintain your HVAC system read our post here.

Choose Prestige Air to Keep Your HVAC Running Optimally. 

If you experience problems with your heating and cooling call Prestige Air. Our expert service professionals have the training and experience to keep your HVAC system in tip-top shape all year long. Call (817) 200-7215 to make sure your heating and cooling are ready for the season!

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Prestige Air proudly serves Northeast Tarrant County and the Fort Worth, Texas area including Hurst, Euless, Bedford, Colleyville, Grapevine, Southlake, Keller, Watauga, Haltom City, and North Richland Hills.

We look forward to serving you and your household!