it provides the responsive feedback necessary for fine-tuned airflow or fluid management

you likely need a new rotary selector switch in addition to the knob

the 669856R is specifically designed for horizontal applications

or visible rust and cracks on the burner tube

Reznor 99250 Conversion Kit 320720-756 it provides the responsive feedbackThe Reznor 99250 Conversion Kit is a vital genuine OEM replacement part specifically engineered for technicians performing field conversions of Reznor heating equipment. This Natural Gas to LP conversion kit is designed to adapt Reznor F and B E series units, specifically the 50,000 BTU models (F50, B50, E50), to operate on liquid propane. As a factory authorized component, it ensures the precise manifold pressure and orifice sizing required to