E18
Remeha
DHW flow detection fault
Furnace shows E18, burner does not start for DHW demand
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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
Blocked DHW flow sensor, Limescale in DHW inlet, Faulty DHW flow switch or turbine, Incorrect wiring to DHW sensor
How to Fix / Troubleshooting
Safety first: Isolate power and close the cold water inlet before removing any DHW components.
- Check DHW flow: Open a hot tap fully and confirm that water flows strongly. If flow is weak, the inlet filter or pipework may be blocked.
- Clean inlet filter: Many Remeha combi units have a mesh filter at the cold water inlet. Isolate and remove the filter, then clean out debris.
- Inspect DHW flow sensor: Remove the flow sensor or switch and check for limescale or debris. Clean or replace as needed.
- Verify wiring: Ensure the DHW flow sensor wiring is correctly connected to the PCB and not damaged.
- Test operation: Restore water and power, then run a hot tap to confirm that the furnace detects flow and starts the burner.
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Repair Difficulty
Medium
3/5
Required Part
DHW Flow Sensor
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