How much does it cost to fix Keston error code Error 20?

Typical repair cost for the Keston Error 20 fault is £150-300 including labour.

Error 20 Emergency

Keston Error 20 Fault Code

Q: What does the Keston Error 20 fault code mean?

Your boiler has detected a flame when it shouldn't be there, so it has shut itself down to ensure your safety.

Also written as ERROR20 — same fault.

The Keston Error 20 fault code means: your boiler has detected a flame when it shouldn't be there, so it has shut itself down to ensure your safety.. It appears on 1 Keston model in our database.

Technical description: False Flame Lockout

Typical repair cost £150-300 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer

Search the official register for a qualified engineer in your area.

Gas Safe Register →

Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like Error 20: no call-out fees, no surprise bills.

Approved partner

Domestic Appliance Guard

Unlimited call-outs, 24/7 helpline, no price-hike promise

Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Keston models that show the Error 20 fault code

Click a model for the full fault code list and model-specific repair notes.

Heat 45 Repair: £150-300

Source

Keston Error 20 fault code information on this page is sourced and cross-checked against the official Keston service / installation manuals for each affected model.

Keston Heat 45 manual (PDF)

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026