E20
Atlantic DHW Priority / Flow Sensor Fault (Combi Furnace)

Furnace displays E20, often associated with integrated domestic hot water (DHW) function on combi models.

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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

Defective DHW flow sensor, Scaled or blocked DHW heat exchanger, Wiring fault between DHW sensor and Atlantic control board

How to Fix / Troubleshooting

Safety: Turn off power and close water isolation valves before working on DHW components.

Steps:

  • Check DHW flow: Open a hot water tap and verify if water flow is normal. Low or no flow may indicate plumbing or filter issues.
  • Inspect flow sensor: Locate the DHW flow sensor on the combi Atlantic furnace. Check for leaks, scale buildup, or damaged wiring.
  • Clean or replace: If accessible, clean the sensor screen or replace the sensor with an Atlantic-approved part.
  • Descale heat exchanger: If scale is suspected, a professional should perform a chemical descaling of the DHW heat exchanger.

Note: DHW-related faults are specific to combi or multi-function Atlantic furnace models.

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Repair Difficulty

Hard 4/5

Required Part

DHW Flow Sensor
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