Controller shows lockout due to safety chain open

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Open high-limit thermostat, Open low-water cutoff (for hydronic systems), Open door interlock switch, Loose wiring in safety loop

Safety: Do not bypass safety devices. Identify and correct the cause.

Steps:

Check manual reset devices: Locate any manual reset high-limit thermostats or low-water cutoffs and reset them if tripped. Investigate why they tripped.
Door/cover switches: Ensure all burner and furnace doors are properly closed so that door interlock switches are engaged.
Visual wiring check: Inspect the safety loop wiring for loose connections at terminals on the WCM/W-FM control and safety devices.

Medium 3/5

High-Limit Thermostat

Check Price on Amazon

We may earn a commission from links on this page.