Duct high temperature limit switches are designed to sense rapid increases in duct temperature, such as those caused by fire. When that high temperature is sensed, the SPST switch inside the Firestat triggers furnace/fans in the duct to shut off, to ensure the potential fire does not spread to the rest of the building. Once the danger has passed, 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. Therefore, a manual switch is the safest route for your duct high limit switch to ensure a potential fire does not spread through your building. To purchase a duct high limit switch, click here.
Simple Reset Procedure for Manual Reset Duct Switches
Now that you grasp the advantage of manual resets, let’s focus on how to reset your Firestat switch. Each Firestat switch contains a manual reset button, which restores the temperature limit once the high-temperature situation has passed. These switches utilize a bimetal coil to activate a set of contacts when heated. When installed in an HVAC duct system, the switch senses air temperature and triggers contact opening at the designated threshold, stopping the fan to prevent the spread of fire or smoke.
Once the contacts have opened, manual intervention is required for reset. However, reset can only occur once the bimetal temperature drops below the set threshold. This manual reset ensures a physical check of the area to verify the elimination of danger before resetting the device, averting further potential damage. This manual intervention is vital, as opposed to automatic resets that lack human oversight.
Upon cooling, the switch is reset using the lever positioned on top of the device. Simply lift the metal flap and allow it to snap back down, resetting the switch mechanism within.
That’s the procedure in its entirety! Firestat switches are straightforward to install and operate. If you have additional questions, be sure to contact us.
