Gas Furnace Limit Switch Function

The flames would raise the temperature inside the unit and have no place to go getting hotter and hotter.

Gas furnace limit switch function.

The limit switch includes a sensor in the heat exchanger to determine when the air is warm enough to circulate. 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 limit switch plays an important role in every normal cycle of the furnace. How it works when your furnace reaches a temperature of more than 350 degrees the roll out switch shuts off.

The fan limit switch also has two other functions. Details about setting the temperature controls on a fan limit switch are. A limit switch also acts as a safety device for your furnace. Function of the limit switch.

It prevents overheating by interrupting the circuit to the gas valve. When the thermostat calls for heat the furnace burners ignite and begin heating the heat exchanger. The function of your furnace limit switch is to tell the fan when to turn off and on depending on the temperature in the home. If the plenum gets too hot the limit switch shuts off the burner.

Just as it determines when the blower assembly should turn on it will also determine when it should turn off. Once the air reaches a preset temperature the limit switch turns on the blower. By keeping the fan off until the supply air plenum is warm the heating furnace limit switch prevents the furnace blower from sending chilly air into the building if the oil or gas burner has not sufficiently heated up the furnace heat exchanger and supply air plenum. When the switch turns off power is cut off to the furnace and the furnace immediately shuts down.

However for your own safety don t attempt to reset the switch without first consulting your furnace s instruction manual. If the temperature inside of the plenum gets too hot it shuts off the gas supply to your burners to prevent your. Combination gas valves used standing pilot furnaces combine. A fan limit switch is a component of a furnace system that determines when the furnace blower assembly for hot air turns on and off.

The switch is wired to the circuits of your furnace s internal power source. For example if the blower motor stopped running then no air would move through the unit. It reads the temperature of the plenum and waits until it gets appropriately warm. Pressure regulation automatic gas control and pilot safety.

A limit switch is a device that s located under your furnace s supply plenum. It also shuts off the blower when the temperature drops to a certain level after the burner has shut off. Essentially this means that it determines when the hot air should be blown through your ventilation system. The limit switch is a safety control switch located on the furnace just below the plenum.

It s possible to reset the switch at home when necessary by following a few simple steps.