Unknown
Boiler will not start on Grant Vortex 15-20

Grant Vortex 15-20 fault code Boiler will not start

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

What the manual says

Manufacturer manual

No fuel supply, no electricity supply, or burner failing to start

From this model's manual
Verified against the Grant/Grant Vortex 15 20 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 Boiler will not start: 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.

All 12 fault codes on the Vortex 15-20

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

26.036.0Boiler operating on overheat thermostatBurner lock-outBurner pulsatesCombustion fumes smellFlame slow to stabilise during start upFumes and puffing during startingOil odoursVisible smoke from flue or high smoke numberWater temperature low

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 →

New boiler cost 2026

Realistic UK prices for a swap.

Read →