it breaks the circuit to the gas valve as a safety measure while keeping the fan energized to cool the heat exchanger

This is typically caused by a failing thermocouple that can no longer generate the 25û30 millivolts required to hold the pilot valve open

it provides versatile SPDT relay wiring configurations for complex sequencing

Can this sensor be used for discharge air monitoring

it monitors blower motor performance to ensure the combustion air fan is generating sufficient static pressure before allowing the gas valve to energize

McDonnell & Miller 349500 Hook-Up 30067439-890 it breaks the circuit toThe McDonnell & Miller 349500, also identified by model number SA159 24, is a specialized lower quick hook up fitting engineered for seamless integration with steam boiler safety controls. This critical component serves as a direct replacement part for the McDonnell & Miller Series 47 and 47 2 mechanical water feeders, as well as the Model 64 A, 42A, 67, and 42S A low water cut offs. Designed for professional installation, it enables a reliable