Hydrolevel 700 Low Water Cut Off 318423 701 The Lennox 18M62 Pressure Switch The Lennox 18M62 Pressure Switch is a critical dual stage furnace component designed for precise combustion air proving in high efficiency heating systems its robust shutoff capabilities and 15 psi steam rating make it ideal for both one pipe and two pipe configurations where an angle valve is required at the radiator inlet the Hydrolevel 700 is frequently installed as a secondary or redundant low water cut off on steam boilers to provide an additional layer of protection alongside the primary control Disclaimer: While we strive for 100% accuracy