E09
Attack Primary Flow Overtemperature / High Limit

Boiler shows E09 and stops; may be associated with very high flow temperature.

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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

Blocked primary heat exchanger on Attack condensing boiler, Airlock in system causing poor circulation, Faulty or stuck circulation pump, Incorrect pump speed setting

How to Fix / Troubleshooting

Safety: Allow boiler and system to cool. Do not repeatedly reset without finding the cause.

Steps:

  • Check system pressure and bleed: Ensure pressure is correct and bleed radiators and high points to remove air.
  • Verify pump operation: With a heat demand, touch the Attack circulation pump. It should vibrate slightly and be warm but not excessively hot. If silent and very hot, it may be seized.
  • Check pump speed: Some Attack pumps have adjustable speed. Ensure it is not set to the lowest setting if the system is large.
  • Inspect filters: Clean any system filter or strainer on the return line to the boiler to improve flow.

Technician: If E09 persists, the primary heat exchanger may be scaled or blocked and should be chemically cleaned or replaced by a professional.

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Repair Difficulty

Medium 3/5

Required Part

Primary Heat Exchanger
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