De Dietrich Overheating of Domestic Hot Water

Water heater produces very hot water, risk of scalding at taps

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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 NTC sensor on De Dietrich unit, Stuck gas valve at high fire, Anti-scald mixing valve failed or misadjusted, Control board temperature regulation fault

How to Fix / Troubleshooting

Safety first: Risk of scalding. Warn occupants and consider turning off the heater until the issue is resolved.

Step-by-step checks:

  • Lower setpoint: Reduce the DHW temperature setpoint on the control panel to 50°C or lower.
  • Check mixing valve: If a thermostatic mixing valve is installed, adjust it to a safer outlet temperature and verify operation by measuring water temperature at a tap.
  • Observe burner cycling: If the burner runs continuously without modulation, note this behavior for the technician.

When to call a professional: Overheating often indicates sensor or control faults and should be inspected by a qualified technician promptly.

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Repair Difficulty

Hard 4/5

Required Part

Thermostatic Mixing Valve
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