Part 45 Description - 4100 Series

The core charging high limit switches are located in the limit zone on the left side of the furnace. These limit switches monitor temperature inside the brick core. If normal operating temperature is exceeded, one or more of the limit switches will open and interrupt power to the heating elements. "CORE FAIL" will flash on the system display. The core charging high limit switches will automatically reset when the temperature returns to a normal range.

If the "CORE FAIL" message occurs repeatedly, verify that the system clearances have not been violated and that the mechanical room temperature has not exceeded 85°F. If clearances and room temperature are correct, it is possible that the system is overcharging, one of the limit switches is defective or a relay expansion board has failed. Failure of the core charging high limit switches is highly unlikely.

Early models used a high temperature ceramic body 410°F limit in conjunction with stainless steel probes that penetrated the insulation panel to read brick core temperature more directly. This limit system was redesigned in August 2002 and replaced by the current 290°F limits without probes.