E12
Potterton
Flow/Return Temperature Differential Fault
Boiler shows E12, may be accompanied by noisy operation or rapid cycling
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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 system or heat exchanger, Pump running at incorrect speed, Air in system, Incorrect bypass setting
How to Fix / Troubleshooting
Safety first: Turn off the boiler and allow it to cool before bleeding radiators or opening valves.
User checks:
- Bleed radiators to remove trapped air and top up pressure afterwards.
- Ensure all radiator valves are open and that thermostatic radiator valves (TRVs) are not all closed.
Engineer checks:
- Check pump speed setting and verify adequate circulation through the system.
- Inspect and clean any system filter or strainer.
- Assess the primary heat exchanger and system pipework for sludge; powerflush if necessary.
- Verify that an automatic bypass valve (if fitted) is correctly set.
Resolving circulation issues usually clears E12 faults.
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Repair Difficulty
Hard
4/5
Required Part
Central Heating Pump
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