How does a high temperature limit switch work?

How a Limit Switch Works. When the air in the plenum reaches the high limit setting on the limit switch, the switch turns on and activates the blower fan, circulating air through the heat exchanger on its way to the house while simultaneously pulling cool air from the house through the air returns and into the furnace.

Where is the high limit switch on a furnace?

It’s also safety device that helps prevent your furnace from overheating. The high limit switch consists of a long temperature-sensing probe attached to a metal mounting plate. From the mounting plate, the switch is wired to the blower fan motor and to the gas valve. The switch is generally located just past the heat exchanger.

Where do I find the limit switch on my hot water heater?

You’ll find this high-level limit switch in your heater cabinet. With the front panel removed, look in the lower-left corner of the cabinet. Attached to the inside left surface you’ll find a white switch with a red push button in its center.

When does the high limit switch turn off?

The energy used to heat that air isn’t wasted. Sometimes the temperature of the supply air inside the furnace drops below a certain temperature. This is when the high limit switch signals the blower motor to turn off. The high limit switch is also an extremely important safety device inside your furnace.

Where is the high level limit switch located?

You’ll find this high level limit switch in your heater cabinet. With the front panel removed, look in the lower left corner of the cabinet. Attached to the inside left surface you’ll find a white switch with a red push button in its center.

Why does my spa heater trip the high limit switch?

The high limit switch can also be tripped by low pressure or water flow. When the water slows down in the heater, this raises the temperature of the water as it exits the heater. Most high limits are set to trip when they sense water temperatures of around 140° .

Where is the high limit switch on a heat exchanger?

The switch is generally located just past the heat exchanger. This is so that it can detect the temperature of the supply air. In other words, the air that’s about to be blown into your home.

Limit switches turn off the burner and turn on the circulating fan if there is a high temperature condition in the furnace. There is a difference between a limit switch and a rollout switch. The limit switch shuts off the burner when the temperature exceeds a preset temperature. When the temperature reduces to normal, the burner will come back on.

What to do if your furnace has an open high temperature switch?

If the furnace failure code indicates an “open limit” or “open high temperature switch” or “open rollout switch”, it is probable that the furnace has overheated. Limit switches turn off the burner and turn on the circulating fan if there is a high temperature condition in the furnace.

Which is HR series high temperature Sealed Switch?

HR Series high temperature hermetically sealed switch is sealed as defined in MIL-PRF-8805, Symbol 5. The HR Series combines maximum sealing, high temperature [315 deg C (600 deg F)] capabilities and rugged, heavy duty, corrosion-resistant

How is a high temperature fuse different from a rollout switch?

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. Some of these parts are shown on the left.

What kind of conditions do temperature switches need to be in?

To protect these switches from splashing water, corrosive liquid, and dust, the housing meets NEMA 4X for washdown conditions. Housing is UL listed for environments with flammable gases, combustible dust, and ignitable fibers, such as chemical plants, refineries, and grain elevators.