this OEM Lennox replacement part is the primary successor for legacy models including LB-50709BB

identical replacement for the C-309-S-T-HH

check your existing hardware to determine if additional port fittings or condensate traps are required for the specific installation

this hardwired thermostat requires both the R (24 VAC) and C (Common) wires for operation

Simplified Installation: Features a slotted cover and unique internal hardware to ensure proper core alignment and rapid assembly

Lochinvar & A.O. Smith 100109972 Control Box 319825-402 this OEM Lennox replacement partThe Lochinvar & A. O. Smith 100109972 Control Box is a critical replacement component designed for precise sequence control and safety monitoring in high efficiency commercial boilers and water heaters. Engineered to interface seamlessly with the integrated control system, this module manages ignition timing, flame sensing, and temperature modulation. Technicians frequently utilize this OEM replacement part to resolve control board failure symptoms