What Is a Limit Switch on a Furnace?

There are several essential components inside the furnace appliance. The furnace limit switch is one of them. Its function is to turn on and off the furnace blower assembly. This switch is also known as a furnace fan limit switch and a furnace high limit switch. Without this vital component, your furnace might endanger your family.

This device is in charge of distributing warm air through the ductwork in the home. Furthermore, the furnace limit switch is designed to turn off the furnace if it overheats. It’s an essential part that impacts how well your furnace functions. As a result, if it starts to malfunction, as all components ultimately do, it is essential to detect the warning symptoms and call an HVAC service immediately. This article discusses the function of a limit switch on a furnace.

What is a furnace limit switch and how does it function?

A limit switch on a furnace is an element of a forced air furnace designed to keep track of the temperature within the appliance. The switch will turn on or off the furnace blower whenever the heating system reaches the desired temperature, ensuring that your house is properly heated. Also when a furnace overheats, the maximum temperature function of limit switches can shut off the regular heating operation. A furnace cannot control the temperature with a thermostat if the limit switch is not operating.

Your furnace runs like follows when everything is normal and the limit switch is working correctly:

• Increase the temperature on the thermostat.
• The burners in the furnace fire up and begin heating air in the plenum.
• When the air is heated to the desired level, the system starts distributing it to the vents through ducts.
• The limit switch then checks the furnace temperature.
• If the furnace becomes too hot, the limit switch turns off the burners and activates the blower fan.
• The limit switch permits the burners to restart when the furnace temperature returns to the usual working range.
• The thermostat then signals the furnace to turn on when the house cools, and the process repeats.
• The high limit switch on the furnace improves the heating capacity.

Limit switch on a furnace and proper furnace operation

A furnace limit switch is crucial for your furnace to operate correctly and to prevent overheating by turning off the blowers and burners. If a furnace becomes too hot, it might cause damage to the equipment and could also be dangerous to the occupants of the building. There would first be a fire danger. However, a broken furnace may let harmful carbon monoxide out.

For this reason, the furnace limit switch is essential. It’s also why a failing switch can cause a furnace to shut off without warning. Heating systems are constructed so that they will not run without a properly functional limit switch for safety reasons.

Homeowners must understand that furnace overheating happens when the blower fan fails to operate or when a furnace filter becomes overly unclean, forcing the machine to strain and overwork. Instead of relying on the limit switch, they can take an active part in maintaining their HVAC system by doing routine maintenance on the furnace and changing the air filter.

Warning signs of a failing limit switch

Aside from the furnace suddenly stopping or short cycling, there are two more signs to check for. The first sign is if the furnace blowers don’t appear to turn off when they should. Moreover, if the air coming out of the vents is chilly rather than warm, this is also an indication.

If your furnace is constantly activating and deactivating throughout the day, this might indicate a problem with the blower motor. The furnace limit switch will be tripped by an overheated blower component, deactivating your furnace before the typical heating cycle is complete.

Also the sensor on the furnace fan limit switch often develops problems as the furnace ages. We advise clearing out any debris from the fan limit switch that may prevent your furnace from functioning properly.

The furnace fan limit switch may also be affected by other common issues, such as broken gas valves, thermostats, or circuits. The switch may also trigger if there are problems with airflow inside the furnace. For example, filthy furnace filters might restrict airflow and cause the switch to trip.

Always check the furnace filter to ensure it is not blocked. The frequency of filter replacement will vary based on the kind of furnace and the filters used. We suggest getting an annual furnace tune-up from a technician to avoid potential problems with your limit switch.

Can I fix the high limit switch on my own?

This procedure may seem straightforward to a skilled HVAC professional or electrician, but it might be difficult for a homeowner. Your home might become prone to fire, carbon monoxide leaks, and other problems if furnace repairs are not done correctly.

We urge that property owners get expert assistance if they detect a problem with their furnace limit switch, given the expense of a replacement HVAC equipment and the associated health and safety dangers.

Conclusion

The limit switch on your furnace is an important safety feature. An inoperative furnace limit switch prevents the furnace from working in tandem with a thermostat to maintain a desired temperature.

If you want your limit switch to function effectively, your furnace must be properly fitted. In the event that it is not, a broad list of continuous or recurrent issues may follow. Following that, preventative maintenance is critical. Some of these chores, such as replacing your furnace filters on a regular basis, will help ensure that your furnace continues to perform effectively.

However, receiving expert servicing on a regular basis is also a smart idea. An HVAC professional can clean and examine your furnace, detecting any little flaws with your system before they become big concerns. Try to find an HVAC supplier and hope they have the skills and attention to detail to fix the issue promptly and fully.