Lochinvar & A.O. Smith 100208474 Connection Board 319852-301 the standard EX4-I21 is a

the standard EX4-I21 is a uni-flow design

For proper flame modulation control

and light oil with a pressure differential range of 5-150 PSI for air/water and up to 100 PSI for oil

as a Factory Authorized Part for the Carrier family of brands

Lochinvar & A.O. Smith 100208474 Connection Board 319852-301 the standard EX4-I21 is aThe Lochinvar & A. O. Smith 100208474 is a critical low voltage connection board designed for seamless integration with Lochinvar Knight WB51 WB211 series wall mount boilers. As an authentic OEM boiler control interface, this component manages the essential signal pathways between the primary control logic and external system accessories. Technicians recognize this board as the central hub for terminal connections, ensuring that thermostat calls,