Ngenic Stuck Heating Relay / Call-for-Heat Latched On

Heating stays on continuously even when the thermostat is set low or turned off.

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Safety Warning

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.

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Possible Causes

Welded relay contacts in Ngenic control module, Miswired boiler terminals permanently bridged, Boiler configured to ignore external thermostat, Software bug keeping relay energized

How to Fix / Troubleshooting

Safety: Turn off power to the boiler and Ngenic control module before inspection.

  • Check thermostat status: Ensure the Ngenic thermostat is not in a manual override or frost protection mode that keeps heat on.
  • Inspect wiring: Verify that there is no permanent link across the boiler’s thermostat terminals in addition to the Ngenic wiring.
  • Power-cycle system: Turn power off for 30 seconds, then back on and observe if heating still runs with no demand.
  • Test relay (advanced): With power off, disconnect one call-for-heat wire from the Ngenic control module. Restore power; if heating stops, the relay may be stuck closed internally.

A stuck relay requires replacement of the Ngenic boiler interface/control module by a qualified technician.

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Repair Difficulty

Professional Required 5/5

Required Part

Ngenic Boiler Interface / Control Module
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