Most appliances are built with safety in mind these days. Furnaces are no different and have a number of built in safety mechanisms in place to help keep you, your home and furnace safe. The limit switch is one of those safety devices! This little electromechanical device has a big job to do. Today JMS Air Conditioning & Heating will be discussing just what a limit switch is and what it does to keep your furnace running optimally at all times.
What Does a Furnace Limit Switch Do?
A limit switch on your furnace is located under your furnace’s supply plenum and is a part of your blower assembly. It is also a part of your overall control system. The limit switch has two main functions. First, it reads the temperature inside your furnace’s plenum and won’t allow the fan to turn on until it reaches the desired temperature. It then sends a signal that the air inside the plenum is warm enough to be delivered by the fan throughout the home. Secondly, it works as a kill switch. If the temperature of the air inside the plenum becomes too hot, it shuts off the gas supply to the furnace’s burners to prevent the heat exchanger or furnace from overheating. If a heat exchanger overheats, it can crack and leak toxic fumes into your home.
What Happens when a Furnace High Limit Switch Keeps Tripping?
A furnace limit switch’s kryptonite is poor air flow. This is most commonly caused by dirty air filters. Lack of proper air flow to your furnace can cause the heat exchanger to overheat repeatedly, which puts excess wear and tear on your limit switch. In time, this will cause the limit switch to malfunction from having to work overtime. One of the most common signs of a broken limit switch is the continuous operation of the furnace’s blower. This is caused by the limit switch’s inability to communicate with the fan when the air has warmed to the desired temperature telling it it’s time to shut off, causing the blower to continually run. Another sign of a bad limit switch would be your furnace not turning on at all! If clogged filters are apart of the problem, then your system can’t get the right amount of airflow needed to operate. If there is not enough air circulating in the system, it will cause the heat exchanger to overheat. Once the limit switch senses the influx in temperature it will shut the burner down, resulting in your furnace not turning on at all. Lastly, old age can also cause a limit switch to stop working properly.
How to Keep Your Furnace Limit Switch Working Efficiently
The simplest thing you can do on your own to ensure your limit switch runs the way it was made to, is to keep your air filters changed regularly. We can not stress enough how important this step is. For a couple of bucks a month, you can keep a strong and steady flow of air going to your furnace with no interruptions which will not only save your limit switch, but the other vital components within your furnace as well. Yearly maintenance performed by JMS Air Conditioning & Heating will ensure your system is running at optimal capacity at all times.
Furnace Heating Repair, Tune Up & More in Van Nuys, Sherman Oaks, Tarzana, Agoura Hills & Greater Los Angeles, California
JMS Air Conditioning & Heating will inspect your limit switch, handle air flow issues and check all vital components on your furnace to check for parts that may be wearing down and need replacing before they cause further damage. This will save you thousands of dollars in the long run and is highly recommended by HVAC professionals everywhere. Give us a call if you have further questions or would like to schedule your furnace’s yearly check-up. We’re happy to help!