E18
Termet
Domestic Hot Water (DHW) NTC Sensor Fault (on combi Termet units)
Display shows E18, furnace may overheat quickly or show inconsistent temperatures.
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
Defective DHW NTC sensor, Loose sensor in DHW heat exchanger, Damaged sensor wiring, Scale buildup affecting sensor response
How to Fix / Troubleshooting
Safety: Turn off power and water supply to the unit. Hot water can cause burns.
- Locate DHW NTC: On combi Termet furnaces/boilers, the DHW sensor is usually mounted on or inside the plate heat exchanger.
- Inspect wiring: Check the two-wire cable and connector for damage or corrosion. Reseat the connector on the PCB.
- Check for scale: If accessible, inspect the DHW heat exchanger for scale buildup. Heavy scaling can cause sensor lag and temperature spikes.
- Measure resistance: Compare sensor resistance to Termet’s NTC chart. Replace if out of range.
If E18 remains after sensor replacement, the control board or DHW hydraulics may need professional diagnosis.
Advertisements
Repair Difficulty
Medium
3/5
Required Part
DHW NTC Temperature Sensor
Check Price on Amazon
We may earn a commission from links on this page.
Advertisements