Switch and Manual Reset Inside a Firestat

Our Firestat switches use a bimetal coil to open a set of contacts when they heat up. However, you may be wondering what these contacts look like, and how they are reset after the switch has been triggered. When placed in an HVAC duct system, it will sense the air temperature. Based on what temperature the device is set at, it will open the contacts whenever that temp is reached, and stop the fan from running and spreading the potential fire or smoke it detected to more areas of the building.

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When the switch heats up, the contacts open as seen in the picture below:








Once the contacts are opened, the switch needs to be manually reset. However, the switch can only be reset once the temperature of the bimetal goes below whatever the switch is set to. This manual reset button reactivates the temperature limit after the high-temperature condition has cleared. It is a manual reset as to make sure someone has to physically check the area to make sure the danger has cleared before the device can be reset back to normal. This prevents any further damage from happening if it were an auto reset and did not require human intervention.

Once the switch cools down, it is reset with the level on the top of the switch, as seen below. You simply pick up on the metal flap and let it “snap” back down, resetting the switch inside the device: 

That’s all there is to it! Firestat switches are easy to install and use. If you have any questions, be sure to contact us.

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