The Lochinvar & A.O. Smith 100309870 Integrated Control Board is an OEM replacement component designed for compatible FB4001–6001 commercial heating boilers. It serves as the system’s central controller, coordinating burner operation, ignition sequences, temperature regulation, and safety functions to support reliable heating performance. The board also assists with system monitoring ... https://www.partshnc.com/lochinvar-a-o-smith-100309870-integrated-control-board