Protherm DHW Priority / Diverter Valve Fault

Boiler provides heating but no domestic hot water

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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

Stuck diverter valve not moving to DHW position, Faulty DHW flow sensor not detecting demand, Failed diverter motor or actuator, Blocked plate heat exchanger

How to Fix / Troubleshooting

Safety: Isolate power and water supply before working on hydraulic components.

Steps:

  • Open a hot tap and observe whether the boiler recognizes DHW demand (flame symbol or DHW icon). If not, test and replace the DHW flow sensor.
  • If demand is recognized but no hot water is produced, check the diverter valve position; manually move it if possible to confirm mechanical freedom.
  • Replace the diverter valve cartridge or motor head if it is stuck or not responding.
  • If the diverter operates correctly, inspect the plate heat exchanger for blockage and clean or replace as needed.
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Repair Difficulty

Hard 4/5

Required Part

Diverter Valve Assembly
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