Worcester Bosch H03 status codewhat it means
Planned maintenance required. The Greenstar i is saying a service interval has passed — H03 counts burner hours, H08 a set date, H13 a number of months. A reminder, not a fault.
Before you start
What H03 means
Worcester's Greenstar i ErP manual sets out a family of maintenance codes, "displayed with the letter H followed by a number", and describes them as advising of "a situation that will need some attention but is not a fault that will stop the appliance from functioning". Three of them are service reminders. H03 means "the number of operating hours set for service interval has expired"; H08 means "the set interview date has expired" — Worcester's word, and they mean interval — and H13 means "the maximum maintenance interval set (in months) has exceeded".
All three show on the display as the text "Planned maintenance required" and can also be read in the maintenance menu. Each has a lower-case twin — h03, h08, h13 — which is the same counter before it has expired, visible only in the menu as confirmation that a reminder is set. Worcester note that the burner-hours option only works if it was enabled by the installer, and that the months interval is set in boiler setting 2.5F, with a value from 1 to 72 and 0 disabling it.
The remedy is the same in each row: reset the maintenance message by pressing the reset button, carry out a service and reset the service reminder. That last part is the engineer's, and it matters — an owner can dismiss the message, but until the reminder is reset from the boiler settings it will return. The other H codes are genuine minor faults rather than reminders: H09 for pump communication, H11 for the hot water sensor, H29 for the outdoor sensor. They have their own pages.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Service interval expired | The installer set a reminder in months, a date, or a number of burner hours, and it has run out. Worcester allow 1 to 72 months in setting 2.5F. | Common |
| Reminder not reset after the last service | The engineer serviced the boiler but did not reset the counter in the boiler settings, so the reminder returns on the old schedule. | Common |
| Boiler recently commissioned | Worcester's H13 row notes the message can appear after the appliance has been placed into commissioning mode, which can trigger it on a new installation. | Occasional |
What to try yourself
Press the reset button briefly to dismiss the message. Worcester's own remedy starts with exactly that, and the boiler continues to run normally whether you do or not.
Book an annual service if one is due. The message is the boiler's way of asking, and on a boiler under guarantee the annual service is a condition of it.
Ask the engineer to reset the service reminder in the boiler settings after the service. Dismissing the message alone does not stop it coming back.
Get a Gas Safe registered engineer to look at your Worcester Bosch H03
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What it costs to fix
Typical repair cost
£80–£150
Time on site
1 hour
Free to dismiss. An annual service is £80–£150 and includes resetting the reminder.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
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Related Worcester Bosch fault codes
- Blue light flashingGet it checkedOn a Greenstar with no display, the blue light is the fault code. Steady means healthy; a flashing pattern, read with the reset button, is a diagnosis Worcester publish in the installation instructions.Related: electronics and power
- F0Get it checkedThe boiler has found a fault inside its own electronics and stopped. F0 covers the control board and the burner control unit, and it needs an engineer.Related: electronics and power
- A7Get it checkedThe hot water temperature sensor has failed. Heating usually carries on as normal while the hot water runs cold, scalding, or swings between the two.Related: electronics and power
- Red light flashingGet it checkedOn a Worcester built before the Greenstar era, the flashing lights are the fault code. Slow means a lockout you can reset once; fast means a fault the boiler is waiting out or an engineer's.Related: electronics and power
- 9U 233Get it checkedThe heat control module is loose, missing or faulty. This small plug-in part carries the identity of your boiler, and nothing runs without it.Related: electronics and power
- Fd 231Get it checkedPower to the boiler was cut while it sat in a lockout, so a fault happened before the interruption. On older Greenstars, Fd simply means the reset button was pressed by mistake.Related: electronics and power
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Related guides
Common questions about Worcester Bosch H03
Is Planned maintenance required a fault?
No. Worcester's manual is explicit that H codes are not faults that stop the appliance functioning. Heating and hot water are unaffected.
Why H03 rather than H08 or H13?
It depends how the installer set the reminder. Burner hours gives H03, a specific date gives H08, and a number of months gives H13. Some installations set more than one.
I see h03 in lower case in the menu. Is that different?
Yes — it is the reminder counting down but not yet expired. Worcester publish the lower-case version as confirmation that a burner-hours interval is set. Nothing to do.
What does the CDi Classic show for this?
SE alternating with the flow temperature. Same reminder, older display, reset through service function 5.A rather than the boiler settings menu.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.