Frequently Asked Questions

It’s simple!

1. Set the temperature dial.
2. Mount the switch downstream of air flow.
3. Wire the switch to your equipment.

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The temperature you’ll need your Firestat to be set at depends on how close you place it to your furnace and how hot your furnace runs. We recommend that you identify where you plan on installing your duct limit switch before you buy it and measure the air temperature when your furnace is running. Once you know that temperature, add about 40°F and that’s what you should set your switch at.

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When mounting a duct limit switch, it’s best if the bi-metal element reaches the middle of the air duct. The air in the middle of the duct is often a different temperature than the air towards the edge of the duct due to change in pressure and turbulence. When air turns or encounters resistance the air flow speed and temperature are affected. 

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1. Remove the cover
2. Adjust the dial to the desired set point
3. Replace the cover & Install

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A limit switch shuts down a piece of equipment versus a fan switch turns equipment on. Click here to learn more!

To ensure the potential fire does not spread to the rest of the building. The manual switch ensures that human interaction is needed in order to reset that switch to allow the furnace/fans to turn back on. If an automatic switch was used and switched the furnace/fans back on too soon, it could cause the potential fire to be spread throughout the building.

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The way Bimetal works is that two different types of metal are fused together. The two metals have different coefficients of thermal expansion, which basically means that they expand at different rates when they heat up. In the case of our switches, the bimetal is in a coil, and the expansion and contraction of the coil is what causes the switch to trigger and open the contacts.

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Our duct limit switches can be a direct replacement option to your Honeywell or Johnson Controls model. Click here to reference your part number to ours!

CEMCO Firestat duct limit switches are manufactured in the U.S.A.

CEMCO firestat duct limit switches can be found worldwide. We can ship directly to you, or you can work with one of our distributors. Click here to contact us today!

CEMCO’s firestat duct limit switch is commonly found with HVAC distributors, and we offer wholesale pricing!  Click here to contact us today!

CEMCO’s firestat duct limit switch is commonly found in large dwellings as a building code requirement. Purchase directly from us for faster lead times and best possible price! Click here to contact us today!