Furnace Limit Switch: What It Is and Why It Matters
For any boiler operator, ensuring your boiler room is in great working condition for the winter months is a top priority. Among the various components that make up your heating system, the furnace limit switch is a crucial but often overlooked part. In this article you will learn what a furnace limit switch is and why it is crucial for your boiler room according to factory certified personnel with over 60 years of experience.
What is a Furnace Limit Switch?
A furnace limit switch is a safety device located within the furnace that monitors the temperature inside the heat exchanger and the blower compartment. Every boiler has a limit switch as it’s a critical component of boiler safety. It serves two primary functions: Preventing Overheating and Controlling the Blower Fan.
Functions of Furnace Limit Switch
Preventing Overheating:
The limit switch ensures that the furnace does not overheat. If the temperature inside the furnace exceeds a pre-defined limit, the switch will shut off the burner to prevent damage to the furnace and reduce the risk of fire. There are many reasons why the temperature could exceed the setpoint, and the manufacturer is typically responsible for defining these setpoints and ensuring the limit switch is calibrated correctly when delivered with the boiler.
Controlling the Blower Fan:
The limit switch also regulates the blower fan. The limit switch turns the fan on when the furnace reaches a certain temperature and off when it cools down. This helps in maintaining an efficient heat distribution throughout your boiler heat application area. The blower fan settings are critical to ensure that the combustion in the boiler is optimized, however, the limit switch only senses temperature and serves no prescriptive function in combustion optimization.
How Does a Furnace Limit Switch Work?
The limit switch is typically composed of a bimetallic strip that responds to temperature changes. When the furnace is operating normally, the strip is flat, allowing the electrical circuit to remain closed, which keeps the burner running. If the furnace overheats, the strip bends, breaking the circuit and shutting off the burner. Frequent cycles in the boiler can contribute to a limit switch failing more often than expected.
Common Issues with Furnace Limit Switches
Based on our experience, we have found that furnace limit switches can experience issues that may affect the performance of your entire heating system. Some common problems include:
Frequent Cycling:
If the furnace limit switch is faulty, it may cause the furnace to cycle on and off frequently. This can lead to inefficient heating and increased energy bills.
Blower Fan Issues:
A malfunctioning limit switch can cause the blower fan to run continuously or not run at all. This can result in uneven heating and uncomfortable indoor temperatures. It can also result in a boiler failure.
Faulty Readings:
Dust, dirt, and debris can accumulate on the limit switch, causing it to give inaccurate temperature readings. This can lead to the furnace shutting down unnecessarily or failing to shut off when it should. Annual cleaning of the boiler can easily address this root cause.
Troubleshooting and Maintenance Tips
The best way to make sure your furnace limit switch remains operational is regular maintenance and timely troubleshooting from factory trained professionals such as Miller Proctor Nickolas, Inc. (“MPN”). This can help prevent limit switch issues and ensure your furnace operates
efficiently. Here are some key troubleshooting and maintenance tips that MPN recommends:
Regular Cleaning:
Keep the area around the limit switch clean. Dust and debris can affect its performance. Use a soft brush or compressed air to clean the switch and its surroundings. Don’t be afraid to call service experts like MPN to assist with cleaning to ensure your system is
operating at peak efficiency.
Professional Inspection:
Schedule annual inspections with a professional boiler technician like the technicians at Miller Proctor Nickolas, Inc. They can check the limit switch and other components for signs of wear and tear and can recommend best practices to keep your boiler
room running at peak efficiency.
Replace When Necessary:
If you notice frequent cycling or blower fan issues, it may be time to replace the limit switch. Consult a professional like Miller Proctor Nickolas, Inc., to ensure the correct part is used and installed properly. There are now new options to replace your limit
switch that professional companies like MPN can recommend. Call MPN today to speak factory certified personnel and learn more.
Monitor Furnace Performance:
Keep an eye on your furnace’s performance. Unusual noises, frequent cycling, or uneven heating can be signs of limit switch problems. These issues are a challenge to diagnose as they may result from a variety of input reasons. Call a professional if these problems persist.
The furnace limit switch plays a vital role in the safe and efficient operation of your heating system. By understanding its function, recognizing common issues causing them to fail, and following regular maintenance tips, you can ensure that your boiler room is operating at peak
efficiency when you need it to most. If you have any questions relating to your boiler room, call MPN today, we are here for all your boiler room needs.