Boiler produces central heating but no domestic hot water on a combi Viadrus boiler.
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.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn off power and close the cold water inlet before opening any DHW components. Beware of hot water and sharp edges.
Step-by-step checks:
- 1. Confirm symptom: Open a hot tap fully. If the boiler does not fire or the heating flow pipe remains the only hot outlet, DHW is not being prioritised.
- 2. Check DHW flow sensor: Clean or replace the DHW flow sensor as described in the E14 scenario.
- 3. Diverter valve check: With a hot tap open, feel the heating flow pipe. If it gets hot instead of the DHW outlet, the diverter valve is stuck in heating mode and likely needs replacement.
- 4. Plate heat exchanger blockage: If the boiler fires but DHW temperature is low and fluctuating, the plate heat exchanger may be scaled or blocked and requires professional cleaning or replacement.
When to stop: Diverter and plate heat exchanger work should be carried out by a qualified technician.
Repair Difficulty
Required Part
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