Lochinvar & A.O. Smith 100277765 Thermal Switch

The Lochinvar & A.O. Smith 100277765 Thermal Switch is a critical safety component designed for high-limit temperature protection in residential and commercial water heaters. This resettable thermal switch functions as a fail-safe, automatically interrupting the burner circuit or gas valve power when it detects temperatures exceeding safe operating parameters. Engineered to replace obsolete part numbers RLY1002 and 100167473, this OEM component ensures seamless compatibility with FVIR (Flammable Vapor Ignition Resistant) systems and high-efficiency gas control valves.

For service technicians, the manual reset capability is a significant advantage over one-time thermal fuses, allowing for rapid system recovery once the underlying overheat condition—such as a blocked vent, scale buildup, or dry fire—has been addressed. This switch is frequently utilized in Lochinvar water heater parts and A.O. Smith ProLine series equipment, providing the precise thermal monitoring required to prevent tank damage and ensure code compliance. Its compact, robust housing is built to withstand the rigorous cycling of modern HVACR environments, maintaining overheat safety protection without premature fatigue.

Key Benefits

• Direct OEM Replacement: Fully compatible internal replacement for Lochinvar 100277765, RLY1002, and 100167473.
• Resettable Design: Features a manual reset button that eliminates the need for part replacement after a standard trip event.
• System Protection: Provides essential HVAC safety shutoff by monitoring combustion chamber and tank surface temperatures.
• Professional Grade: Heavy-duty construction designed for the high-temperature demands of gas-fired water heating systems.
• Reduced Downtime: Simplifies troubleshooting and restores operation quickly after safety protocols are triggered.

Common Questions

How do I know if my Lochinvar 100277765 Thermal Switch has tripped?
If your water heater's pilot won't light or the burner fails to engage despite having gas pressure, check the back of the switch. If the center button is popped out, the switch has tripped due to an overheat condition. Press the button to reset after the system has cooled.

Can I use this switch to replace a non-resettable ECO?
No, this manual reset thermal switch is specifically designed for air intake or burner door monitoring. It should only be used as a direct replacement for the part numbers specified in your equipment’s service manual.

What causes this resettable thermal switch to trip frequently?
Frequent tripping usually indicates restricted airflow, a clogged flame arrestor, or improper venting. As a safety limit switch, it is reacting to unsafe internal temperatures that must be corrected by a technician to ensure long-term performance.

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.