The Nordyne 660303R Orifice is a precision-engineered OEM replacement part specifically designed for LP (Liquid Propane) gas configurations in 66 Series furnaces

ensuring the damper closes fully and maintains tight shut-off

System Safety: Functions as a primary rollout limit switch or high-limit safety to prevent heat exchanger damage

eliminating the risk of dimensional mismatch

Schneider Electric (Barber Colman) AT-520-40 Knob Kit The Nordyne 660303R Orifice isThe Schneider Electric (Barber Colman) AT 520 40 Knob Kit is a critical replacement component for field technicians managing pneumatic control systems and legacy HVAC automation hardware. This setpoint knob kit is specifically engineered to provide a precision fit for Barber Colman TK Series thermostats, ensuring accurate calibration and tactile adjustment of space temperature setpoints. Built from high impact, industrial grade plastic, the AT 520 40