The McDonnell & Miller 312200 Gasket is a critical replacement valve bracket gasket engineered specifically for Series 21

Using a certified furnace pressure switch with the correct WC rating is essential for maintaining the system's AFUE rating and overall operational safety

disrupting the electrical circuit to the burner or heating elements should the plenum temperatures exceed safe operating parameters

Like all hot surface ignitors

The Rheem-Ruud 43-17075-11 Start Capacitor is a high-duty electrical component engineered to provide the necessary torque for compressor and motor startup in residential and commercial HVAC systems

Armstrong Furnace R42936-001 Discharge Thermostat The McDonnell & Miller 312200The Armstrong Furnace R42936 001 Discharge Thermostat is a critical high limit safety component engineered specifically for HVAC discharge temperature monitoring. Designed to integrate seamlessly with Armstrong and AirEase furnace models, this limit switch monitors heat exchanger temperatures to prevent thermal runaway. When discharge temperatures exceed factory set parameters, the R42936 001 interrupts the heating circuit, protecting the heat