HVAC Hacks: Tips for Novices and New Homeowners

Does the Limit Switch in Your Furnace Trip Excessively? Learn the Causes

In order to achieve the ideal indoor environment during the cold season, all the parts of your furnace should be in optimal working condition. When a component fails, the heating system becomes inefficient or may stop working. One of the popular furnace issues you're likely to experience is a limit switch that keeps tripping. This issue can result from various factors, including the following: 

You Have an Oversized Furnace

When your furnace is excessively large for your house, you should expect the limit switch to trip. Remember that the limit switch helps shut down the furnace as soon as it detects something wrong in its operations. The downside of such a furnace is that it releases a lot of heat at once, which isn't evenly distributed across your home. This causes your furnace to run and shut down within short intervals, forcing your limit switch to trip. The only way to determine the right furnace size for your home is to call a heating repair service to perform load calculations.

You Have Air Flow Issues

Insufficient flow of air to the furnace also contributes to excess tripping of a limit switch. For instance, when the air duct is blocked, or the air filter is dirty, it is highly likely that the heat exchanger will overheat. As a result, your limit switch will trip. Therefore, excess tripping—accompanied by an overheating heat exchanger—signals restricted airflow. You'll need to call a heating professional to replace the air filter and clean your furnace air passages when faced with this situation.

Your Flame Sensor Is Filled with Dirt

In most furnaces, the limit switch features a sensor rod responsible for detecting fluctuations in temperature within the furnace plenum. But when it's filled with dirt, it won't efficiently detect indoor temperatures, and this could result in limit switch tripping. If a dirty sensor rod is the cause of your problem, consider cleaning it.

The first step during cleaning is to find the location of the switch, which is usually behind the access panel of your furnace. Then, you should remove the switch, clean it gently with steel wool to remove soot, and return it carefully. If these steps don't solve your problem, seek the help of a heating expert.

Your Limit Switch Could Be Faulty

After prolonged use, your limit switch will begin to experience wear and tear, rendering it ineffective. In addition, a faulty limit switch can trip when the temperatures are low, resulting in short cycling.

Keep in mind that the limit switch plays a crucial role in safeguarding your furnace against overheating. So, if it keeps tripping, other healthy components can suffer damage due to excess heat. Call your furnace repair service immediately if you notice unusual tripping of the limit switch.