This is a self-powered millivolt valve typically used with a 750mV thermopile or a 250mV–750mV system

protecting the silicone diaphragm and calibration spring from industrial wear

or if you measure infinite resistance (OL) on a multimeter while the switch is at room temperature

Safety Standard Compliance: Engineered to meet the rigorous demands of safety shutoff and vent valve regulations in fuel-fired equipment

Lochinvar & A.O. Smith 100109675 Flue Baffle Assembly 320735-701 This is a self-powered millivoltThe Lochinvar & A. O. Smith 100109675 Flue Baffle Assembly is a critical internal component engineered for high efficiency commercial boilers and water heaters. As a veteran technician knows, the flue baffle assembly is essential for optimizing heat transfer by slowing down the velocity of combustion gases, allowing more dwell time within the heat exchanger. This OEM Lochinvar part (also listed across the A. O. Smith replacement parts catalog) is