TC Duct Limit Switches, by CEMCO


Senasys acquired the CEMCO TC duct limit switch product line in 2014. Many of our other switching products sense air or surface temperature making this product line fit well within our family! Since acquiring the product line we have made a number of improvements including technical support, more custom options and testing.

For more information about the TC duct limit switches, read below.

To purchase a duct limit switch or send a request for quote, please click here to contact our direct technical support team.


Duct Limit Switch Common ApplicationDuct limit switches are used in HVAC systems to shut off heating, ventilation, and air conditioning equipment. They detect air temperature and trigger an SPST switch once the temperature reaches a set limit, which could happen if a machine overheats, or a fire starts. The temperature limit is then reset using a manual reset button once the surrounding temperature drops below the temperature limit. These switches come in both fixed temperature and adjustable temperature variants.

Fixed and Adjustable Temperatures

The fixed temperature switch has standard temperature settings at 125°F, 165°F, and 200°F. You can also contact us about custom temperature settings if you need something different. Our adjustable temperature switch can be set by the operator to sense 100°F to 250°F. The adjustable switches also have different element lengths (5”, 7.5”, and 11”). Like the temperature, you can get a custom element length, but you’ll need to contact us. Both the fixed and adjustable switches are open on temperature rise, meaning that they break the circuit once the surrounding temperature reaches the predefined temperature.

Duct Limit Temperature Switch Product Details

The Duct High Temperature Switches feature a helix bimetal element that senses rapid increases in duct temperature, such as those caused by fire. The high temperature limit then operates an SPST switch that opens with a rise in temperature. A manual reset button reactivates the temperature limit after the high-temperature condition has cleared. These duct high temperature limits are indispensable in specialized HVAC applications and Building Automation Systems.

Learn More About Duct Limit Switches

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