Beretta DHW Temperature Oscillation

Water heater temperature fluctuates: hot-cold-hot during a shower

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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

Partially blocked DHW flow sensor, Oversized or modulating tap/shower mixer, Faulty DHW NTC sensor, Incorrect minimum gas rate adjustment

How to Fix / Troubleshooting

Safety: Beware of sudden hot water temperature spikes that can cause scalding.

  • 1. Test with a simple tap: Run hot water from a basic basin tap (no thermostatic mixer). If temperature is stable there, the issue may be with the shower mixer, not the heater.
  • 2. Clean DHW flow sensor: Limescale or debris can cause erratic flow readings. A technician should remove and clean or replace the flow sensor.
  • 3. Check DHW NTC sensor: Verify that the sensor is firmly attached and not affected by poor contact or corrosion.
  • 4. Gas adjustment (technician): A Beretta-trained technician can adjust minimum and maximum gas rates to ensure stable modulation at low flows.
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Repair Difficulty

Medium 3/5

Required Part

DHW flow sensor
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