Furnace High Limit Switch

The high limit switch in your gas furnace is a small part with two very important jobs.

Furnace high limit switch.

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. As a safety the high limit. The high temperature limit switch is an important device used in forced air furnaces powered by gas or heating oil. Note that the limit switch has nothing to do with the thermostat.

The switch makes sure the furnace is operating safely and at its desired settings. They will be mounted near where the flame may rollout the front of the furnace due to venting blockages heat. Some of these parts are shown on the left. The high limit switch shuts down the furnace at a set limit so a clog doesn t burn out the system.

This is the role it plays in every cycle of your furnace s normal operation. The blower will continue to run until either the system is reset or the limit switch closes. For example if the blower motor stopped running then no air would move through the unit. High limit switch a high limit control switch will turn off the gas to a furnace if the temperature becomes too high.

The limit switch is a safety switch that monitors t. If the high limit switch was bad the furnace should not fire. Depending on your furnace model the switch will be surrounded by a silver or white cover. Turning the fan motor on and off is the high limit switch s main job.

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. The limit switch includes a sensor in the heat exchanger to. I believe high limit switches are normally closed and.

It reads the temperature of the plenum and waits until it gets appropriately warm. Locate the white limit switch. It s also known as a fan limit switch or simply a limit switch. Rather it is wired in series with the 24 volt control circuit of your furnace.

If the blower came on at the same time as the burner it would pump cold air through the house at first. The flames would raise the temperature inside the unit and have no place to go getting hotter and hotter. 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. A pair of wires is connected to the switch.

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