E22
Keston Supply Voltage / Brownout Fault

Boiler intermittently shows E22, particularly after power cuts or brownouts

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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

Low mains voltage, Loose supply connections, Faulty PCB power supply section, Shared circuit overload

How to Fix / Troubleshooting

Safety: Electrical work must be carried out by a competent person. Isolate power before inspection.

User checks:

  • Note if other electrical devices flicker or reset at the same time; this may indicate a supply issue.
  • Avoid running high-load appliances on the same circuit as the boiler if possible.

Engineer checks:

  • Measure mains voltage at the Keston boiler during operation; ensure it is within specified limits.
  • Inspect the fused spur, plug, and wiring for loose connections or overheating.
  • If supply is stable but E22 persists, test the PCB power supply section and replace the PCB if faulty.
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Repair Difficulty

Medium 3/5

Required Part

Main Control PCB
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