Medium
299 on Navien NCM 1130HH

Your boiler's secondary burner sensor is incorrectly registering a flame when the burner is actually turned off.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Ionisation probe of supplementary burner detected false flame

From this model's manual
Verified against the Navien/Navien Ncm 1130hh installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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 →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like 299: 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.

Related fault codes

290View →291View →

All 77 fault codes on the NCM 1130HH

Seeing a different code? Every code this model can display, in one place.

96979899100102114116117118121122127157158164187253254257258259260261262263264265266267268269270271272273274275276277278280281282283284285286287288289290291292293294295296298300301302303304305306307308309310311319394395396397

Related guides you might find useful

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

Boiler service cost

What a UK service costs and what a proper one includes.

Read →