The Velocity Boiler Works (Crown) 960123 M/R Spill Switch is a safety device designed to monitor flue gas spillage in compatible gas-fired heating equipment. It works by sensing abnormal temperatures caused by combustion gases escaping from the draft hood or venting system and interrupts the burner operation when unsafe conditions are detected. This spill switch is commonly used in Cr... https://www.partshnc.com/960123-velocity-boiler-works-crown-spill-switch-mr