Peerless Boiler Will Not Shut Off / Control Fault

Boiler runs continuously and overshoots thermostat setting

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

Stuck relay on control board, thermostat contacts stuck closed, miswired TT circuit

Safety first: Turn off power if boiler will not stop firing.

Steps:

Check thermostat: Remove the thermostat from its base or disconnect the TT wires at the boiler. If the boiler stops, the issue is in the thermostat or wiring.
Inspect TT wiring: Look for shorts between thermostat wires.
Control relay: If boiler continues to run with TT open, the control relay may be stuck and the control board should be replaced by a technician.

Hard 4/5

Boiler control board

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