A12
Hoval
DHW Flow Detection Fault
Boiler displays A12, no hot water in DHW mode, heating may still 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
Faulty DHW flow sensor or turbine, Blocked DHW filter, Limescale in plate heat exchanger restricting flow, Wiring fault to DHW sensor
How to Fix / Troubleshooting
Safety: Isolate power and close water isolation valves before opening any water components.
- Check DHW flow: Open a hot tap fully. If flow is weak, clean or replace any inlet filters or strainers on the cold water inlet to the Hoval boiler.
- DHW flow sensor: On combi models, remove and inspect the DHW flow sensor/turbine for debris. Clean gently and ensure it spins freely.
- Plate heat exchanger: Heavy limescale can restrict flow and cause sensor errors. In hard water areas, a technician may need to chemically descale or replace the DHW plate heat exchanger.
- Wiring: Check the connector from the DHW flow sensor to the PCB for secure contact.
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Repair Difficulty
Hard
4/5
Required Part
DHW Flow Sensor / Turbine
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