White-Rodgers 3L11-210 Limit Switch

For high-limit protection in commercial and residential HVAC systems, the White-Rodgers 3L11-210 Limit Switch (equivalent to Therm-O-Disc 36T21-10858) offers precise temperature monitoring and circuit interruption. This 1/2" bimetal disc thermostat is engineered with a SPST (Single Pole Single Throw) configuration and Normally Closed contacts that are designed to Open on Rise between 204°F and 216°F. This specific temperature range is critical for preventing heat exchanger overheating and ensuring system safety. The device features an auto-reset function with a 30°F differential, meaning the limit will re-close once the temperature drops back down to approximately 174–186°F. Built for durability, the 3L11-210 includes an aluminum disc cup for rapid thermal response and stainless steel mounting brackets with a loose ring to facilitate various mounting orientations. With a 15A resistive rating at 120VAC and 10A at 240VAC, this snap action disc thermostat provides a reliable, cost-effective solution for gas and electric furnaces.

Key Benefits:

• Reliable fixed temperature limit control with a factory-set 204–216°F operating range.
• Automatic reset eliminates the need for manual intervention after the system cools down.
• Engineered for versatility with 1/4" quick connect terminations for fast field replacement.
• High-speed contact separation ensures a long lifecycle and consistent high-limit protection performance.
• Broad compatibility as a direct White-Rodgers 36T21-10858 replacement in many OEM heating units.

Common Questions:

What is the difference between Open on Rise and Close on Rise for this switch?
The White-Rodgers 3L11-210 is an Open on Rise switch, meaning it acts as a safety limit. It breaks the electrical circuit when the sensed temperature exceeds 216°F to stop the heating process. A "Close on Rise" switch would do the opposite, usually to activate a cooling fan.

Can this be mounted in a different position than the original?
Yes, the included loose ring mounting bracket allows for flexible installation, though it is standard practice to ensure the bimetal disc maintains optimal thermal contact with the surface or air stream being monitored for accurate sensing.

How do I verify if this fits my furnace?
Contractors should match the temperature range (210°F nominal) and the 3L11-210 or 36T21-10858 part numbers. This 1/2" disc is a standard sizing for many residential and light commercial fan and limit controls.

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.