When Is A Dual Fan/Limit Switch Useful?

Firestat Duct Control

Senasys has been playing with the idea of manufacturing a dual fan/limit switch for quite some time now, so as we begin planning this project, we thought it would be helpful to our customers to hear why this product is useful, and what the difference is between and dual fan/limit switch and the limit switch we do currently offer.

Click Here to take a look at our Firestat Limit Switch options!

These Firestat duct limit switches that we currently offer are installed in air ducts to shut down heating, air conditioning and ventilation equipment when air temperature inside the duct exceeds a pre-set limit. 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, including apartment buildings. The adjustable duct limit switch can be set by the operator to sense 100°F to 250°F, and our standard fixed temperatures include, 125°F, 165°F or 200°F.

A dual fan/limit switch works the same way the limit switch does, it simply has the ability to not only turn off the fan on the limit side, but it has the ability to turn the fan on as well. When the air temperature rises inside the duct where the unit is mounted, (meaning the furnace is on and running) it triggers the unit at a certain set temperature to close the contacts and turn on the fan to disperse the hot air through the ducts.  As soon as the temperature in the duct begins to fall back down to normal inside the duct, (meaning the furnace is no longer running) it triggers the unit at a certain set temperature to open the contacts and turn the fan back off, as to not blow cold air through the ducts after the furnace is done running. (Note: If the temperature continues to rise past the set “fan on” temperature, and reaches that high limit pre-set temperature, this is when it triggers the contacts to break and the fan to turn off to ensure no smoke or fire gets blown and spread through the ducts. At this point it would have to be manually reset.)

Click Here to check out our Firestat Limit Switches! 

And as always, Contact Us Here with any questions or inquiries you may have, or to place an order!

Stay tuned in 2022 as we develop and release our dual fan/limit switch! Read more about it here! 

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