White-Rodgers 3L09-10 Limit Switch

As a field tech, you know that a failing furnace high limit switch can shut down a call before it even starts. The White-Rodgers 3L09-10 is a specialized board mount limit control engineered for precision sensing in gas and electric heating systems. Featuring a 1/2" bimetal disc, this component provides high-speed contact separation with an open on rise switch action. It is factory-calibrated to trip at a 200 degrees F fixed open temperature and reset when the system cools to a 160 degrees F fixed close temperature. Designed for direct attachment to control boards via its 3.12" insertion probe, it effectively monitors localized temperatures near heat-sensitive electronics. This automatic reset limit switch is a reliable HVAC OEM replacement part compatible with various 36T series applications, handling up to 15A resistive at 120VAC. Rely on this snap disc limit control to maintain safe operating parameters and prevent overtemperature conditions in demanding residential or commercial equipment enclosures.

• Precision Thermal Protection: Fixed 200°F cutout protects heat exchangers and control boards from catastrophic overheating.
• Integrated Board Mounting: 3.12-inch insertion length allows the bimetal disc to sit directly in the critical airflow path near the control assembly.
• Automatic Reset Logic: Safely restarts the heating circuit once the temperature drops to the 160°F threshold, reducing unnecessary manual resets.
• High-Speed Contact Separation: Snap-action bimetal element ensures rapid switching to prevent arcing and extend the life of the internal SPST contacts.
• OEM-Grade Construction: Built by White-Rodgers to meet the exact electrical and mechanical specs of original equipment manufacturers.

What causes a limit switch like the 3L09-10 to trip frequently?
Technicians usually find that frequent tripping is caused by restricted airflow, such as a clogged 16x25x1 filter, a failing blower motor, or undersized ductwork. If the switch remains open after the system has cooled, the bimetal disc may have suffered mechanical fatigue.

Can I use this as a substitute for a surface-mount snap disc?
No. This is a board mount limit control specifically designed with a 3.12" probe for insertion through a control board or bracket. Surface-mount discs lack the necessary probe length to sense air temperature in these specific enclosure configurations.

Is the 3L09-10 compatible with 240V circuits?
Yes, this switch is rated for 13A resistive and 2.9 FLA at 240VAC, making it suitable for both 120V gas furnaces and 240V electric heating sections, as well as 125 VA pilot duty applications.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.