Pennco Stuck Relay / Control Fault

Boiler runs continuously even when thermostat is satisfied

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 circulator relay on control board, Shorted thermostat wiring, Zone valve end switch stuck closed, Faulty integrated control logic

Safety first: Turn off power before working on wiring.

Check thermostat: Remove thermostat from its base or disconnect thermostat wires at the boiler. If boiler continues to run, the issue is not the thermostat.
Inspect zone controls: For systems with zone valves, check if an end switch is stuck closed by disconnecting its wires.
Control board: If boiler still runs with all call-for-heat circuits open, the relay on the Pennco control board may be stuck and the board will need replacement.

Hard 4/5

Boiler Integrated Control Board

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