What is a high-temperature limit switch on a furnace?

With the winter season at its peak, the use of furnaces is also quite high. Mishandling of the furnace results in a lot of damage. To prevent this, a limit switch is installed in the furnace.

You can contact professionals for furnace repair in Monterey, CA if there is some problem with your limit switch. A high-temperature limit switch is a safety device used in all kinds of furnaces.

What Does a Limit Switch Look Like?

The limit switch consists of a temperature sensing probe joining a mounting plate. This sensor probe is put inside the furnace, whereas the mounting plate is placed outside.

A wire connects the blower fan and the fuel valve and is placed in the mounting plate. Multiple limit switches are utilised to measure the furnace temperature at various points. In older devices, the limit switch lies outside the furnace, but nowadays, it lies inside the cover panel.

How Does the Limit Switch Work?

The limit switch functions are controlling the blower fan and restricting the fuel supply.

When the furnace operates, the heat exchanger begins to heat up. At this time, the air is not warm. Thus, the limit switch keeps the blower off. When the air becomes warm enough to be circulated, the blower fan is turned on.

After the room has attained a sufficiently warm temperature, the burner is turned off. The limit switch is then turned off until the next cycle. If the heat exchanger gets extremely hot at any point, the limit switch cuts off the power supply, which would otherwise damage the device.

Problems Due To Malfunctioning Limit Switch

Sometimes, the limit switch does not do its job properly. This results in:

Continuously running blower fan:The blower fan does not turn off even after the burner has stopped and has become cool.

Hard shutdown: If the limit switch has to shut down the burner four to five times, it enters hard shutdown mode. This indicates an in-built error in the limit switch, and it needs to be replaced. The furnace will stop working until further service is done.

Replacing a Limit Switch

If you have a damaged limit switch, you should call a furnace repair in Monterey, CA, to help. People who know about circuits and multimeters tend to replace the limit switch independently.
You can also follow the steps below to replace your limit switch as well:

  • Turn off the power to the furnace.
  • Remove the already existing limit switch.
  • With the help of the multimeter, check the resistance. If it is infinity, it means your switch is damaged.
  • Fix the new limit switch with the help of screws.
  • Your limit switch has been replaced.

We, MPH Heating and Air provide you with all the essential HVAC services to cater to your needs. You can find detailed information about our HVAC-related services on our website.