Furnace High Limit Switch

Turning the fan motor on and off is the high limit switch s main job.

Furnace high limit switch.

The limit switch includes a sensor in the heat exchanger to. If the blower came on at the same time as the burner it would pump cold air through the house at first. I believe high limit switches are normally closed and. The switch makes sure the furnace is operating safely and at its desired settings.

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. It s also known as a fan limit switch or simply a limit switch. Locate the white limit switch. A pair of wires is connected to the switch.

Note that the limit switch has nothing to do with the thermostat. As a safety the high limit. The flames would raise the temperature inside the unit and have no place to go getting hotter and hotter. Depending on your furnace model the switch will be surrounded by a silver or white cover.

When the high limit switch trips the flame heating element will be shut off and the blower will continue to run to clear the heat. A limit switch is a device that s located under your furnace s supply plenum. It reads the temperature of the plenum and waits until it gets appropriately warm. This switch plays a role in the normal operation of your furnace.

This is the role it plays in every cycle of your furnace s normal operation. They will be mounted near where the flame may rollout the front of the furnace due to venting blockages heat. The high limit switch in your gas furnace is a small part with two very important jobs. High limit switch a high limit control switch will turn off the gas to a furnace if the temperature becomes too high.

Rollout switches and high temperature fuses are different from limit switches in that when they open they will not close again unless reset as in the case of the rollout switch or replaced as in the case of the high temperature fuse. The high limit switch shuts down the furnace at a set limit so a clog doesn t burn out the system. The blower will continue to run until either the system is reset or the limit switch closes. If the high limit switch was bad the furnace should not fire.

For example if the blower motor stopped running then no air would move through the unit. The limit switch is a safety switch that monitors t. Some of these parts are shown on the left. The high temperature limit switch is an important device used in forced air furnaces powered by gas or heating oil.

In this episode of repair and replace vance shows how to replace the high limit switch in a gas furnace.