Lennox 47K20 Transformer meaning it is set to

meaning it is set to open the circuit at a fixed 150°F high-limit threshold and features a 30°F differential for automatic reset

If your diagnostics reveal furnace short cycling or 4-flash error codes

The Eaton C25DND330B is the primary cross-reference for the 42BF35AG

it maintains strict capacitance tolerances and high insulation resistance to prevent premature failure during frequent cycling

While the adapter provides the mechanical connection

Lennox 47K20 Transformer meaning it is set toThe Lennox 47K20 Transformer is a heavy duty step down control transformer engineered for high demand HVAC low voltage control circuits. Designed to provide a reliable 24V secondary output from a 208 240V primary input, this 40VA Class 2 transformer ensures consistent power delivery to contactors, relays, and integrated furnace control boards. This unit is a direct OEM replacement part and is technically identical to the Lennox 47K2001 and the