Low
H13 on Worcester Bosch Greenstar i

Your boiler is simply reminding you that it is time for its annual safety service, as set by the installer, rather than indicating a mechanical breakdown.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

A time has been set in the Service interval function i.e. 1 to 72 months and that time has expired. Service reminder time in the Boiler settings menu (section6.5.13, page43) allows this feature to be set (1 to 72), a 0 will disable this function.

From this model's manual
Verified against the Worcester Bosch Greenstar I installation & service manual, page 63.
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

Monthly cover means no unexpected bills when your boiler breaks down.

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 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 →