Gas Furnace Limit Switch Function

Furnace fan limit switches also include a maximum temperature function that will disable the standard heating process if the furnace overheats.

Gas furnace limit switch function.

This one demonstrates the effect of high temperatures on the gas furnace. It reads the temperature of the plenum and waits until it gets appropriately warm. A high limit control switch will turn off the gas to a furnace if the temperature becomes too high. Lastly the furnace fan limit switch may also be accompanied by a manual on switch that allows you to keep the fan activated continuously throughout the day in your home to improve air flow.

The high temperature limit switch is a small but important device used in forced air furnaces powered by natural gas lp or heating oil. Once the plenum reaches a specific temperature the limit switch sends a signal to the air handler to begin running and delivering warm air to your home. The fan limit switch on a heating furnace controls when the furnace blower fan turns on and off. It turns the fan on and off during the normal heating cycles of the furnace and it senses heat and shuts down the furnace if the interior temperature gets too high.

The flames would raise the temperature inside the unit and have no place to go getting hotter and hotter. A limit switch is a device that s located under your furnace s supply plenum. The limit switch includes a sensor in the heat exchanger to determine. This control also provides a safety limit that turns off the burner or furnace if temperatures at the furnace are too high.

For example if the blower motor stopped running then no air would move through the unit. This video is part of the heating and cooling series of training videos made to acc. A limit switch also acts as a safety device for your furnace.