E15
NTI
Low Voltage / Power Supply Fault
Boiler displays E15; may indicate low 24V or power supply fault; intermittent resets
Advertisements
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.
Advertisements
Possible Causes
Undersized or loose power wiring, Faulty transformer or power supply on control board, Brownouts or unstable mains, Short on low‑voltage circuit
How to Fix / Troubleshooting
Safety: Power work should be done with the breaker off and verified with a meter.
- Check supply voltage: Measure line voltage at the boiler input. It should be within the range specified by NTI (typically 120V ±10%).
- Inspect connections: Tighten all line and neutral connections at the boiler’s terminal block. Look for discoloration or melted insulation.
- Low‑voltage short: Disconnect thermostat and accessory wiring one circuit at a time to see if E15 clears, indicating a shorted external device.
- Board/transformer: If supply is stable and wiring is good, the internal transformer or power supply section of the control board may be failing and should be replaced by a technician.
Advertisements
Repair Difficulty
Hard
4/5
Required Part
Control Board Power Supply Section
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements