E15
Main
Flow/Return Temperature Differential Too High
Boiler displays E15, often with rapid temperature rise and shutdown
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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
Insufficient circulation, Pump running at low speed, Blocked radiators or valves, Sludged system
How to Fix / Troubleshooting
Safety: Allow the system to cool before touching pipework or radiators.
- Open all radiator valves: Ensure TRVs and lockshield valves are open, especially on radiators near the boiler.
- Bleed radiators: Remove trapped air from all radiators and towel rails, starting upstairs.
- Check pump setting: If the Main boiler has adjustable pump speed, set it to a higher setting to improve circulation.
- Engineer checks:
- Measure temperature difference between flow and return; if excessive, inspect for blockages.
- Clean or replace any system filters and flush the system if heavily sludged.
- Replace the Main pump assembly if it cannot provide adequate flow.
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Repair Difficulty
Medium
3/5
Required Part
Circulating Pump
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