Worcester Bosch SE status codewhat it means
SE alternating with the temperature on a CDi Classic is a service reminder, not a fault. The burner has run the hours Worcester equate to a year, and the boiler wants its annual check.
Before you start
What SE means
On the Greenstar CDi Classic and its Heatronic 3 relatives the display normally shows the flow temperature. When it starts alternating that temperature with SE, the boiler is telling you it is due a service. Worcester's engineer booklet explains the mechanism: "the burner has run for 2324 hours since the boiler has been checked last", 2324 hours being Worcester's average of a year's burner running time. The booklet then asks the engineer a sensible question — when was the boiler actually checked last?
If it was twelve months or more ago, do the annual combustion and safety check. If it was more recent, the burner has simply run for longer than average, probably at lower output and higher efficiency, and there is no need to check the boiler yet. Either way the code is cleared through the service menu, function 5.A, which is an engineer procedure involving holding the service button until it glows orange and stepping through the menu with the eco button. It cannot be cleared by the reset button and it does not need to be, because it does not stop the boiler doing anything.
Heating and hot water continue exactly as before. The Greenstar i and the 8000 Life do the same job with text — "Planned maintenance required" and the H03, H08 and H13 maintenance codes — so if your display is showing words rather than SE, that page is the one you want.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| A year's burner hours have accumulated | Worcester's threshold is 2324 hours of burner operation since the reminder was last reset, which they take to represent twelve months of typical use. | Common |
| Reminder not reset at the last service | If the engineer serviced the boiler but did not clear function 5.A, the counter carried on from where it was and the reminder arrives early. | Common |
| Heavy use | A boiler running a large house or one left on constant reaches 2324 hours well inside a year. Worcester's booklet says this alone is not a reason to service early. | Occasional |
What to try yourself
Check when the boiler was last serviced. If it is a year or more, book an annual service with a Gas Safe registered engineer — that is all the code is asking for.
Ask the engineer to reset the service reminder through service function 5.A when they have finished. If they do not, SE will return before its time.
Do not press reset repeatedly to try to clear it. SE is not a lockout, the reset button has no effect on it, and the boiler is running normally underneath.
Get a Gas Safe registered engineer to look at your Worcester Bosch SE
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
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
Own a Worcester Bosch boiler? Save it and its codes come first next time.
Related guides
Common questions about Worcester Bosch SE
Is the boiler safe to use while SE is showing?
Yes. Worcester describe SE as a service reminder and it does not interrupt operation. It is asking for the annual check that keeps the boiler efficient and the guarantee valid.
Can I clear it myself?
Not without entering the service menu, which Worcester document for engineers. The sequence involves holding the service button for ten seconds and stepping to function 5.A. Leave it for the engineer at the service visit.
What does the Greenstar i show instead?
Words. The Greenstar i and the 8000 ranges display Planned maintenance required and log an H code — H03 for burner hours, H08 for a set date, H13 for a set interval in months. Same idea, different display.
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.