De Dietrich
No Domestic Hot Water Production
Boiler runs but produces no domestic hot water (combi or system with cylinder)
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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
Faulty DHW flow sensor, stuck diverter valve, scaled plate heat exchanger, cylinder thermostat fault (for system boilers)
How to Fix / Troubleshooting
Safety: Turn off power and close water valves before removing water components.
- Check boiler response: Open a hot tap fully. The boiler should recognise demand (DHW symbol on display). If not, suspect the DHW flow sensor.
- Feel pipes: On combi models, the primary flow pipe may get hot but DHW outlet remains cold if the plate heat exchanger is blocked or the diverter valve is stuck.
- Cylinder systems: Check the cylinder thermostat and motorised valve operation. Ensure the cylinder stat is calling for heat.
- Technician tasks: Clean or replace the plate heat exchanger, replace the DHW flow sensor, or repair the diverter valve as required.
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Repair Difficulty
Medium
3/5
Required Part
Plate Heat Exchanger (DHW)
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