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Bartels Heating & Cooling Blog

The Limit Switch: A Key Mechanism for Furnace Safety and Regular Operation


We like to educate our customers about the basics of their HVAC systems. Just a bit of knowledge can go a long way in helping homeowners like you recognize potential problems in their comfort systems and understand the best way to save money through efficient operation. 

Today, we’re going to discuss a key part of a gas furnace (the heating system you most likely have). It’s the limit switch, which does several important jobs that keep a furnace running—and running safely and efficiently.

If you have issues with your furnace limit switch in Middletown or elsewhere in our service area, contact us right away to have the problem inspected and repaired.

The Furnace Switch Basics

The furnace limit switch is a critical component in a gas furnace. It plays a pivotal role in maintaining safety and efficiency. Essentially, the limit switch monitors and regulates the temperature inside the furnace. 

Here are the main jobs of the limit switch:

  • Temperature monitoring: The primary function of the limit switch is to monitor the temperature within the furnace. It is strategically placed in the plenum, which is the chamber where heated air collects before it is distributed throughout the home.
  • Safety control: In order to prevent a gas furnace from overheating, the limit switch acts as a safety control device. If the temperature inside the plenum exceeds its predetermined safe limit, it means the heat exchanger is overheating. The limit switch then triggers to shut off the flow of gas to the burners. This prevents potential damage to the interior of the furnace as well as combustion dangers outside of it. 
  • Fan activation: Beyond safety measures, the limit switch also plays a role in regulating the operation of the HVAC system’s blower fan. Once the furnace has reached the desired temperature, the limit switch signals the fan to start circulating the air around the heat exchanger and then into the ductwork and the living spaces. 
  • Maintaining a consistent temperature: The limit switch helps to maintain a consistent and comfortable temperature inside a house. By cycling the furnace on and off based on the set temperature limits, it helps to prevent uneven heating around the home, preventing cold spots or hot spots in rooms.
  • Energy efficiency: The limit switch helps with energy efficiency. By preventing the furnace from running excessively or at unsafe temperatures, the switch helps prevent excessive energy waste. This helps to keep heating bills under control and contributes to the furnace lasting for longer.

Furnace Limit Switch Trouble

Like any component in a machine, the limit switch can malfunction. Several problems can arise from this: the furnace shutting off and turning on at the wrong times, uneven heating, and the furnace refusing to stay on long enough to provide any heat to the house. Don’t ignore these signs, because if the limit switch is broken you want it fixed to prevent any safety issues. Only trust the pros with this job. Our team is ready to help!

Bartels Heating & Cooling has served Hamilton, OH Since 1973. Contact us for 24/7 emergency service for your heating system.

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