Triangle Tube
Fan Stuck On / Post-Purge Control Issue
Boiler fan runs continuously even when there is no call for heat
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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
Control board relay stuck closed, Faulty fan speed control, Incorrect wiring causing constant power, Software fault
How to Fix / Troubleshooting
Safety: Turn off power before accessing the control board.
- Step 1 – Confirm post-purge: After a heating cycle, the Triangle Tube boiler may run the fan for a short post-purge. This is normal for a few minutes.
- Step 2 – Check thermostat and demand: Ensure there is truly no call for heat or DHW. Turn thermostats down and close hot water taps.
- Step 3 – Power cycle: Turn off power for 30 seconds, then restore. If the fan starts immediately and runs continuously, a relay may be stuck.
- Professional service: A technician should test the control board and fan wiring and replace the main control if the fan output is stuck on.
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Repair Difficulty
Medium
3/5
Required Part
Main Control Board
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