Your boiler has locked out and the display shows an error code. Here is what it means and what you can safely check yourself before calling an engineer.
What the code means
The boiler has detected low water pressure in the heating circuit, usually below 0.5 bar. It is a safety lockout, not a fault in itself.
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Common causes
| Cause | Sign | Fix |
|---|---|---|
| Low pressure | Gauge under 1 bar | Repressurise |
| Leak | Pressure keeps dropping | Check radiators |
| Faulty sensor | Gauge fine | Call an engineer |
How to fix it
Open the filling loop slowly until the gauge reads 1.2 to 1.5 bar, then close it and press reset.
Never remove the boiler casing yourself.
What it costs
A visit from a Gas Safe engineer costs £80 to £150 in most of the UK.
FAQs
Is it safe to repressurise my boiler?
Yes, using the filling loop is a normal homeowner task.
Why does the pressure keep dropping?
Usually a small leak or a faulty pressure relief valve.