E15
Dettson DHW Sensor / Priority Fault

Boiler displays E15 and domestic hot water (DHW) priority is not functioning correctly

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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

Failed Dettson DHW temperature sensor, Faulty DHW flow switch, Incorrect DHW priority wiring, Control parameter misconfiguration

How to Fix / Troubleshooting

Safety: Turn off power before accessing DHW sensors or wiring. Hot water can scald; allow components to cool.

  • Check DHW demand: Open a hot water tap and verify that the DHW flow switch or sensor is being activated (you may hear a click or see a status change on the control).
  • Inspect DHW sensor: Locate the Dettson DHW tank or plate heat exchanger sensor. Ensure it is firmly attached and wiring is intact.
  • Review control settings: In the boiler menu, confirm DHW priority is enabled and temperature setpoints are reasonable per the Dettson manual.
  • Replace faulty components: If the DHW sensor reads incorrectly or the flow switch does not close when water flows, they should be replaced by a technician.
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Repair Difficulty

Medium 3/5

Required Part

Dettson DHW temperature sensor
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