E05
NTI
Low Water Pressure / Water Sensor Fault
Boiler displays E05 and will not fire; may occur after power outage or wiring work
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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
Insufficient system pressure, Faulty pressure sensor, Leaking system or automatic air vent, Closed fill valve from expansion tank or feed line
How to Fix / Troubleshooting
Safety: Do not over‑pressurize the system. Typical cold fill pressure is around 12 psi for a two‑story home; check your NTI manual for exact values.
- Read system pressure: Check the boiler’s pressure gauge or digital reading. If below the minimum (often 10–12 psi), the boiler will lock out.
- Top up system: Open the manual fill valve or fast‑fill lever on the pressure reducing valve to add water until the gauge reaches the recommended pressure. Close the valve afterward.
- Bleed air: Bleed radiators and high points, then recheck and adjust pressure again.
- Inspect for leaks: Look around the boiler, relief valve discharge, expansion tank, and visible piping for signs of water. Repair leaks before repeatedly refilling.
- Check pressure sensor: If pressure is normal but E05 persists, the NTI water pressure sensor or low‑water cutoff may be faulty. A technician can test and replace the sensor.
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Repair Difficulty
Medium
3/5
Required Part
Water Pressure Sensor
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