Lochinvar & A.O. Smith 100278104 Switch 321702-401 Field Accessible: Features a hidden

Field Accessible: Features a hidden local access port for rapid system troubleshooting and configuration without removing the cover

If the pilot stays lit but the main burner fails to ignite

High Conductivity: Non-Teflon design ensures a solid electrical ground and reliable sensing for conductance-type controls

Optimized Air-Fuel Mixture: Maintains the critical seal necessary to prevent vacuum leaks that can destabilize high-altitude or low-NOx burner performance

Lochinvar & A.O. Smith 100278104 Switch 321702-401 Field Accessible: Features a hiddenThe Lochinvar & A. O. Smith 100278104 Switch is a critical safety component designed for high performance hydronic and domestic hot water systems. This 100F manual reset limit switch acts as a primary thermal safeguard, effectively monitoring surface or water temperatures and interrupting the electrical circuit to the gas valve if the 100 degree Fahrenheit threshold is exceeded. Engineering for reliability, this manual reset high limit switch prevents