Marley Engineered Products 4520-0011-002 Limit Switch or a loss of system

or a loss of system pressure that cannot be attributed to the expansion tank or air vents

though typical pilot signals range higher depending on the specific module

making it the standard replacement for various mid-to-high-efficiency Lennox units

Engineered specifically for suction valve assemblies

Marley Engineered Products 4520-0011-002 Limit Switch or a loss of systemAs a seasoned technician, you know that a reliable furnace limit switch is the primary line of defense against heat exchanger failure and fire hazards. The Marley Engineered Products 4520 0011 002 is a high performance linear limit protector designed for precision in demanding industrial and commercial heating applications. This 325F CO AUTO limit switch is engineered to monitor temperatures within the plenum and automatically interrupt the heating