McDonnell & Miller 310488 Switch Assembly R-410A this switch is "normally closed"

this switch is "normally closed" and should show near-zero resistance

contractors can maintain system integrity without replacing entire valve bodies

It is frequently used for oil return lines and pressure sensor ports

Replace your compromised or scaled-out water heater elements with the Bradford White 415-48642-00

and Luxaire air handlers to restore factory-specified static pressure

McDonnell & Miller 310488 Switch Assembly R-410A this switch is "normally closed"The McDonnell & Miller 310488 is a field replaceable SWA 42S Snap Switch Assembly engineered specifically for Series 42S low water cut off and pump controllers. This single pole, single throw (SPST) mechanism provides precise automatic reset functionality, ensuring consistent boiler feed pump control and high limit safety across residential, commercial, and industrial steam applications. Built with a robust housing and high quality internal contacts,