the 030620 is specifically designated as the direct replacement for water and air applications

Is an external vent line required

Equal percentage flow characteristic on the A-port for stable modulation

Simplified Installation: Pre-formed bends eliminate the need for manual pipe threading and bending in the field

meaning it will re-close the circuit once the water temperature drops below the fixed or adjustable differential

McDonnell & Miller 309000 Resistor Kit Refrigerant the 030620 is specifically designatedThe McDonnell & Miller 309000 Resistor Kit, specifically the Model 7B 1R, is a critical slide wire resistor assembly engineered for proportional signal control in industrial boiler systems. This 135 ohm resistor kit is designed to interface directly with 7B switches, providing the necessary modulating signal for precise burner control and water level management. As a veteran grade replacement part, it is compatible with the Series 93, Series 193,