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Greenstar Servicing
Worcester Bosch Boiler Service in London
Worcester Bosch is the make we are asked about more than any other in London, and it is also the one where guarantee length is most often misunderstood. Two Greenstar boilers on the same street can carry very different cover, and the difference is decided at installation by the range, the accessory fitted alongside it and who registered it.
Quick answer
Worcester guarantee lengths run from five to twelve years depending on the Greenstar range, and only some ranges gain anything from a system filter. What every one of them requires is registration within 30 days of installation and an annual service, with the service details recorded and available for inspection on request.
The filter only helps on some ranges — and that catches people out
Worcester publishes a guarantee length per Greenstar range, and then a separate uplift if a Greenstar System Filter is fitted. The uplift is where the confusion sits, because it does not apply across the board. At the time of writing the Greenstar 8000+ and 8000+ Style carry eight years as standard, rising to ten years with a Greenstar System Filter. The Greenstar 4000, CDi Compact and Ri carry seven years as standard, rising to eight with the filter. But the Greenstar 2000 stays at seven years and the Greenstar 1000 stays at five whether a filter is fitted or not.
There is one more trap worth knowing. Worcester’s System Filter Micro does not extend the guarantee at all — only the full Greenstar System Filter does. If you were told a filter was fitted to secure a longer guarantee, which filter it is matters.
The top tier is separate again. Worcester’s twelve year length applies to the 8000+ ranges when the boiler is installed with a Greenstar System Filter by a Worcester Accredited Installer or Worcester Bosch Accredited Partner, with an upgrade fee payable through the installer’s loyalty account and waived for scheme members. All of that is fixed at installation time and cannot be added retrospectively at a service.
Worcester’s guarantee terms then set the conditions that keep whatever was registered alive. The product must be registered within 30 days of installation, and it must be serviced annually by Bosch or any other competent and officially certified engineer, with the service details recorded in the service record and available for inspection on request. Note what that does and does not say: it does not require a Worcester engineer, and it does not name Benchmark in the contractual terms — the Benchmark service record requirement appears in Worcester’s product manuals instead.
Worcester also runs a separate ten year guarantee on the primary heat exchanger, its "heatcell", and that one has its own condition: a corrosion inhibitor must be present in a clean primary system, with the strength of the inhibitor checked every two years and a record of the service findings left with the householder. Worcester’s oil-fired boilers sit apart from all of this, with a much shorter two year standard guarantee.
- Registration within 30 days of installation.
- An annual service by Bosch or any other competent and officially certified engineer.
- Service details recorded in the service record and available for inspection on request.
- For the filter uplift: a full Greenstar System Filter, not a System Filter Micro — and only on the ranges where an uplift exists.
- For the top tier: installation by a Worcester Accredited Installer or Accredited Partner, decided at installation.
- For the ten year heat exchanger guarantee: inhibitor present, with its strength checked every two years.
This page sets out how Worcester structures its Greenstar guarantees, what the annual service has to evidence, the two different fault code conventions Worcester uses depending on the boiler’s age, and what our engineers check on a Greenstar specifically. We service Worcester Bosch boilers as an independent Gas Safe registered firm.
Why the inhibitor check matters more on a Worcester than most people realise
Worcester’s ten year primary heat exchanger guarantee is conditional on a corrosion inhibitor being introduced into a clean primary system, and on the effectiveness or strength of that inhibitor being checked every two years. That is a specific, testable requirement, and it sits alongside a general exclusion in Worcester’s terms for damage caused by water quality — scale, sludge and blockages are not covered.
BS 7593:2019, the British Standard covering preparation, commissioning and maintenance of domestic heating systems, points the same way: clean the system before dosing it with inhibitor, install a permanent in-line filter capturing both magnetic and non-magnetic debris, and service that filter as part of the annual boiler service. On a Greenstar, the standard and the guarantee terms are asking for the same thing.
So on a Worcester the water side is not an afterthought at the end of the visit. We check the inhibitor, open and clean the filter, and write down what was found — because on this brand that record is doing real work if a heat exchanger claim is ever made.
The service reminder that is not a fault
Worcester Bosch boilers display symbols for normal operating modes as well as faults, and homeowners routinely mistake them for breakdowns. Siphon fill mode runs the boiler at a low burn for roughly fifteen minutes to fill the condensate trap. Air purge mode does not fire the boiler at all but pulses the pump on and off. Both are normal on start-up, and Worcester suggests calling if either lasts beyond about thirty minutes.
The one that generates the most unnecessary call-outs is the service reminder. Worcester is explicit that it is not a fault: it appears when the burner service interval of 2,324 hours has run out. A boiler showing it is telling you a service is due, not that it has broken. If yours is showing it, you are on this page for the right reason.
Worcester’s condensate design is worth knowing about too. Current Greenstar boilers use a large-volume siphonic trap that discharges every ten to twenty minutes rather than trickling continuously, which Worcester describes as significantly reducing freezing potential in sustained cold. Cleaning that siphon is a named task in the service instructions — and Worcester’s guarantee terms specifically exclude thawing a frozen condensate pipe as a homeowner responsibility, so the design detail has a direct financial consequence.
What we do differently on a Greenstar
The core annual service applies to every gas boiler: full internal inspection, flue and ventilation check, combustion analysis, and safety device testing. On a Worcester there are additions that come from how the guarantee is written and how the appliance reports itself.
We check the inhibitor and the filter, read the stored fault information off the display properly, clean the condensate siphon, and produce a written record in a form that would stand up if Worcester asked to inspect it. On boilers fitted with a code plug — a physical plug that sets the appliance’s functions and has to be changed on a gas conversion — we check it is the right one, because a mismatched plug generates its own faults.
Model ranges
Greenstar ranges you will find in London homes
Worcester has used the Greenstar name across several generations, and London’s housing stock means we see all of them — a fifteen-year-old CDi in a Victorian conversion and a current 8000+ in a new-build flat, sometimes on the same day. The range matters at a service because it sets the guarantee length, the fault code convention and parts availability.
| Range | Roughly when | What it means at a service |
|---|---|---|
| Greenstar 8000+ / 8000+ Style | Current flagship | Eight years as standard, ten with a Greenstar System Filter, and twelve when installed by an accredited installer or partner with an upgrade fee. Superseded the earlier 8000 Life and 8000 Style. |
| Greenstar 4000 / CDi Compact / Ri | Current mid range | Seven years as standard, rising to eight with a Greenstar System Filter and ten via the accredited installer route. |
| Greenstar 2000 | Current value range | Seven years, with no uplift from fitting a filter. A very common London replacement boiler. |
| Greenstar 1000 | Run-out / recently discontinued | Five years, with no uplift from a filter. Appears on Worcester’s guarantee table but not its current product listing. |
| Greenstar i / Si Compact / CDi Classic / Highflow | Superseded, still widely installed | Very common across London. Mostly out of guarantee now, so the service is about condition and safety. These use the older alert-code-plus-three-digit fault convention. |
| Greenstar Heatslave II / Danesmoor | Oil-fired, outer London | Oil rather than gas, a different competence and checklist, and a much shorter two year standard guarantee — five with a filter. |
Fault codes
Worcester uses two fault code conventions — check which one you have
Older Greenstar boilers — the CDi Classic, i, Si and CDi Compact era — display a two-character alert code plus a three digit number underneath it. Worcester’s own user manual is explicit that both matter: when reporting a fault it is useful to quote the alert code and the three digit number under it, for example EA and 227. Reporting only "EA" throws away most of the diagnostic information.
Current Greenstar 4000 and 8000 boilers have a text display and use a different system entirely: a plain numeric code with a plain-English description alongside it, categorised as operating, blocking, locking or maintenance. If your display shows words rather than a two-character code, you are on the newer system and the older lookups will not apply.
Worcester also categorises older codes by how the boiler behaves: some disable it until the power is cycled, some until the cause is removed, some allow limited function, and some lock the appliance until the reset button is held for three seconds.
EA
During operation: flame not detected
Worcester directs you to check, if safe to do so, that the gas is on in the property, that the condensate pipe is not frozen, and that the flue outlet is not blocked. In London this is overwhelmingly a frozen condensate in a cold snap.
A1
Controlled characteristic pump has run dry
A circulation fault rather than a combustion one. Often points at low system pressure, air in the system, or a pump that is not moving water as it should.
E9
Safety temperature circuit has tripped
The boiler has shut down on an over-temperature safety device. Frequently a circulation problem — a stuck pump, a closed valve, or a system heavily fouled with sludge — rather than a fault in the boiler itself.
C6
Fan speed too low
The fan is not reaching the speed the boiler expects. The appliance will not fire without a proven fan, so this is a hard stop rather than an intermittent nuisance.
b1
Code plug not detected
Worcester boilers carry a physical code plug that sets the appliance’s functions and must be changed on a gas conversion. A missing or wrong plug is its own distinct fault, and quite specific to this brand.
227 / 2971 / 1018
Newer numeric format
On current 4000 and 8000 boilers, 227 is no flame signal after ignition, 2971 is system pressure too low — Worcester notes it triggers between 0.6 and 0.3 bar — and 1018 is simply that the maintenance interval has expired.
Codes and meanings are taken from Worcester Bosch’s own published literature and support pages at the time of writing, and vary between models, generations and revisions — always check the manual for your specific appliance. Ignition, sensor, PCB and gas valve faults are work for a Gas Safe registered engineer, not a homeowner.
On the day
On a Worcester, the record has to survive inspection
Worcester’s terms require the service details to be recorded and available for inspection on request, and its heat exchanger guarantee requires the inhibitor strength to be checked every two years with the findings left with the householder. That makes the paperwork part of the job rather than an afterthought.
- Inhibitor presence and strength checked, and the finding written down.
- The system filter located, opened and cleaned — and we note whether it is a full Greenstar System Filter or a Micro.
- The condensate siphon cleaned, which is a named task in Worcester’s own service instructions.
- Stored fault information read off the display, with the three digit number where the boiler uses that convention.
- A written service record handed over on the day, ready for your guarantee file.
- Anything found that needs further work is quoted separately, never bundled into the service.
Worth checking before you book
- 1Find the range name on the front of the boiler — Greenstar 1000, 2000, 4000, 8000+, i or CDi.
- 2Check whether there is a filter on the pipework near the boiler, and if you can, whether it is a full system filter or a Micro.
- 3Note any code showing, including the three digit number underneath it if there is one.
- 4Find out roughly when the boiler was installed — the 30 day registration window starts there.
We are an independent servicing company. We are not an approved, accredited or affiliated installer for Worcester Bosch, and we have no partnership with them. We service Worcester Bosch boilers as an independent Gas Safe registered firm, working to the manufacturer's published service instructions for the appliance in front of us.
Worcester Bosch servicing questions
Does having my Worcester Bosch serviced by an independent engineer affect the guarantee?
Worcester’s published condition is that the product is serviced annually by Bosch or any other competent and officially certified engineer, with the service details recorded and available for inspection on request. So an independent Gas Safe registered engineer is explicitly contemplated. We are not a Worcester Accredited Installer and we do not claim to be — we service the appliance to the manufacturer’s published instructions and give you a written record every visit.
My Greenstar says a service is due. Has it broken down?
No. Worcester’s service reminder appears when the burner service interval of 2,324 hours has run out. It is not a fault — the boiler is telling you a service is due, and booking one is the correct response.
Will fitting a system filter extend my guarantee?
Only on some ranges. At the time of writing the 8000+ ranges gain two years with a Greenstar System Filter and the 4000, CDi Compact and Ri gain one, but the Greenstar 2000 and 1000 gain nothing. And Worcester’s System Filter Micro does not extend the guarantee at all — only the full Greenstar System Filter does.
Why does my neighbour’s Greenstar have a longer guarantee than mine?
Usually the installation rather than the boiler. Worcester’s twelve year tier requires installation by a Worcester Accredited Installer or Accredited Partner with a system filter and an upgrade fee paid through the installer’s loyalty account. That is fixed at installation and cannot be added later at a service.
Is a frozen condensate pipe covered by the guarantee?
No. Worcester’s terms specifically list thawing frozen condensate pipes, along with re-pressurising, resetting and bleeding, as homeowner responsibilities rather than guarantee work. Current Greenstar boilers use a large-volume siphonic trap partly to reduce that risk, but it does not eliminate it in a hard freeze.
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ReadLondon coverage
Worcester Bosch servicing across all 33 boroughs
The same fully Gas Safe registered engineers from Barking to Richmond. Pick a borough for local detail, or book directly.
Greenstar due a service?
Tell us the Greenstar range and your postcode. We will confirm the visit and the quote before you book, and you get a written record on the day for your guarantee file.
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