🟢 Worcester Greenstar 8000 / 4000 — Bosch EMS numeric codes

Greenstar 8000 Life & Style (GR8300iW / GR8700iW), 8000+ , 4000 · combi, system and regular

Read this first

• These ranges do not use the EA / E9 / C6 / CE codes from the older Greenstar i, Si and CDi tabs. Completely different platform.
• Codes are 3–4 digits with a category letter: O = operating (normal, not a fault) · W = warning / maintenance, boiler keeps running · B = blocking, clears itself when the condition goes · V = locking, needs a manual reset.
• Reset is via the display menu on the 8000, not a dedicated button. Older Greenstar habits (hold reset, or crank the dial anticlockwise to the reset symbol) don't apply here.
• A 200-series code on the screen is usually the boiler telling you what it's doing, not a fault. Don't chase it.

Operating codes — NOT faults

Ignition & flame — the money codes

Field tip that saves callbacks: on any of the flame codes, check the ceramic insulator isn't damaged. A cracked insulator lets the spark earth out and mimics an electrode or PCB fault. Twist and pull the insulator to check it's intact. Also check the earth tags on the boiler and on the electrodes, and the rectification ground — the black wire to the heat exchanger.

Gas valve & code plug

Van stock note: the code plug is the one that catches people out. Fit a replacement PCB without moving the original code plug across and you'll sit there with a 360 or 2946 wondering what you've broken.

Water flow, pressure & overheat

Read 2964 and 2967 as circulation faults, not sensor faults. The most common real cause is a sensor that has come away from the flow pipe or lost contact with it, or a system that isn't circulating — sludge, closed valve, seized pump. Check the physical contact of the sensor before you order one.

Sensors

Symptoms with no code on the display

Codes and remedies from Worcester Bosch Greenstar 8000 Life installation & maintenance documentation. Categories and code sets vary slightly between models in the range — check the manual for the specific GC number on the job.

🔵 Ideal Logic Max / Logic+ / Vogue — current code set

Consistent across Logic, Logic+, Logic Max, Vogue and Vogue Max — combi, system and regular

Good news with Ideal: they've kept one code system across the range for years, so what you know from a Logic still applies to a Logic Max. The letter matters — L = lockout (needs reset), F = fault (usually clears itself when the condition goes).

The customer-facing bit worth saying out loud

When you arrive at an LC or a reset-lockout, the customer has usually been hammering the reset button for two days. Explain that every failed reset puts the boiler through another ignition cycle and accelerates wear. One reset is reasonable; after that the code plus one failed reset is all an engineer needs. Customers who understand that stop doing it, and you stop getting called back to the same house.

Verify against the installation manual for the specific model — Ideal occasionally varies the set between the combi, system and regular variants.

🇮🇹 Sime — "ALL" fault codes

Murelle (HE / Pro HE / Advanced / Elite / EV), Brava Slim, Format, Edea, Go, Mia, Planet

How it displays

• Faults show as ALL followed by the number — e.g. ALL 04 for a DHW sensor fault.
• Some older/commercial models in the range show it as AL instead of ALL. Same numbering logic.
• Reset: when the alarm number appears with the reset symbol, hold the reset button for about 3 seconds.
• Before repairing: main switch to OFF, and close the gas isolation valve as a precaution.

Full ALL code list

ALL 09 — read this before you quote a PCB

ALL 09 means the flow switch has told the PCB there isn't enough circulation. The boiler stops; if the condition holds for more than a minute it waits roughly six minutes before retrying. That intermittent stop-start pattern gets misread as a failing PCB constantly.

Work through, in order: jammed or failed pump · blocked filter · closed flow or return valves · blocked/sludged system · and the flow switch itself. A stuck flow switch reports no flow when circulation is fine. If you've proved good flow through the boiler including the heat exchanger and it's still throwing ALL 09, the switch is the suspect before the board.

Useful PAR parameters

PAR 35 is worth remembering — if a Sime is throwing persistent ALL 09 and the previous engineer has changed the pressure device, check this is set to match what's actually fitted.

From Sime Murelle Advanced HE ErP installation & servicing instructions. The ALL set is largely consistent across the Sime range but individual models vary — confirm against the manual for the GC number on the job.

🇮🇹 Sime — current range map & the Revolution 30

What Sime actually sell now, and which of it the ALL codes above cover

Current Sime UK lineup

The ALL code table above applies across most of this range — Sime has kept one alarm system for a long time, which is why the Murelle codes carry over to Brava, Edea, Go and Mia. That's the opposite of what Worcester did with the 8000.

Murelle Revolution 30 — the one to actually know about

This is the significant recent Sime product and it's unlike anything else in the playbook. A 30 kW Murelle gas boiler and a sealed 4 kW heat pump in one wall-hung case — installed like a conventional boiler, inside, on the wall.

• Any Gas Safe registered engineer can install it. The refrigerant circuit is sealed, so there's no requirement for an F-gas registered installer to attend. That's the commercial point of the product, and it's the reason it's worth you knowing about it.
• Heat pump leads, boiler backs it up. Claimed average seasonal heating performance around 134%, ErP A++.
• Sime have been doing hybrid wall-hung units since 2014, so this isn't a first attempt — but the fully integrated single-case version is the current one.

Why it matters to you specifically: it's the cheapest legitimate route into hybrid work without F-gas, on a customer base that isn't ready for a full heat pump. Worth pricing one as an option on a combi swap quote where the customer asks about "going greener" — you can answer the question properly instead of losing the conversation.

Range list from Sime UK product listings. Revolution 30 specification from manufacturer and distributor material. Verify current availability — Sime revise the range regularly.

🇮🇹 Sime Edea & Giulia — the two ranges worth knowing separately

Edea 30/40, System-T, HM, BF, Hybrid Eco EV · Giulia compact

Edea — the outdoor-capable one

The thing that catches people out: the Edea range is designed so it can be fitted outdoors as well as in. If you get called to an Edea and can't find it, check outside before you ring the customer back. It also changes the fault picture:

• Condensate freezing is a much bigger risk on an outdoor install. An ALL 18 (condensate level) or ALL 06 (no flame) on an outdoor Edea in January is the condensate until proven otherwise. Check the siphon and the external run first, every time.
• Frost protection depends on power staying on. Customers who switch it off at the isolator "to save money" in winter will freeze it — worth saying on the service visit.
• Weather exposure on electrics and connections. Check seals, glands and the case for water ingress on any intermittent electrical fault before condemning a PCB.

Design note: the Edea heat exchanger uses large waterways paired with a high-efficiency modulating pump, aimed at giving good hot water delivery without a cylinder. Large waterways help with sludge tolerance, but the modulating pump is still a real component — spin-test it on any circulation code (ALL 09, ALL 07).

Edea Hybrid Eco EV 25/55 is a second Sime hybrid alongside the Revolution 30. Same warning applies: the ALL codes cover the gas side only. Get the manual before you take one on.

Giulia — the compact cupboard-fit

Two models, among the lightest and most compact in the Sime range. Slim enough to go in a cupboard, which is exactly where you'll find them — usually a tight kitchen unit in a flat or small terrace.

Cupboard-fit caution: compact boilers in tight cupboards mean clearances, ventilation and flue routing get compromised by whoever fitted it. On any Giulia service, check the clearances against the manual and check the cupboard hasn't since been packed with the customer's belongings — that's an ordinary-looking service visit that can turn into a GIUSP call.

Giulia specification from Sime product listings; Edea range and design detail from Sime UK material. Confirm current UK availability and the exact model variants — Sime revise the range regularly, and not every model on the Italian listing reaches the UK.

🔴 Baxi 600 / 800 (incl. 630) & Main — current ranges

Baxi 600 & 800 combi / system / heat · Baxi 400 · Main Eco Compact & Eco Elite · Platinum+ · Megaflo

Where Main sits

Main is a Baxi Group brand and shares the platform and code set. Main Eco Compact and Eco Elite read as Baxi — the existing Baxi / Main / Potterton panel applies. Parts are frequently the same item under a different number, so check the Baxi equivalent before paying a premium for a Main-badged part.

Core codes (manual-derived)

Two display quirks worth knowing

• Codes alternate on two-digit displays. E133 shows as "E1" then "33". If you glance at it mid-cycle you'll misread it. Wait and watch a full cycle before writing it down.
• Some Baxi 600 Heat units use flashing green/red LEDs instead of a numbered code. If there's no number on the appliance you're not looking in the wrong place — get the manual and count the flashes.

Reset

On the selector-switch models, turn the selector to Reset and hold for a minimum of 5 seconds to relight after E110, E130 and E133.

E119, E125 and E133 definitions taken from Baxi Duo-tec installation documentation and confirmed as shared across the 600/800 range. Confirm against the label inside the casing flap on the job — that list is the authority for the specific unit.

📋 Not yet covered — don't guess these on site

Current ranges this playbook does not have verified data for

These are on walls locally and the playbook has nothing reliable for them yet. Until they're added, work from the manufacturer's manual on the job rather than assuming the older code set carries over:

• Vaillant ecoTEC plus / exclusive, 2020 platform onwards — newer VUW variants with the updated display. The F.xx codes on the Vaillant tab cover the older platform.
• Baxi 900 series — 600 and 800 are now covered above; 900 is not.
• Potterton Assure, Ravenheat, Ariston, Biasi, Halstead, Keston, Chaffoteaux — little or nothing in here.
• Viessmann Vitodens 050-W, 100-W B1KF / B1HF — Series B is a different control platform to the older Vitodens entries.
• Ideal Logic Max2 — the newest revision; the table above is the established Ideal set and may not be complete for it.
• Alpha E-Tec, Intergas Xclusive / Xtreme, Glow-worm Energy7.
• Hybrids and heat pump changeovers — nothing in here at all.

Rule for the van: if the boiler is under about six years old and the code doesn't match anything in this playbook, that's the playbook being out of date — not you misreading it. Go to the manual.

🧪 Tightness Testing — IGEM/UP/1B Edition 4

Published March 2026 · mandatory 1 Oct 2026 · natural gas, LPG and LPG/Air

What actually changed

• Permissible drop is now driven by Installation Volume (IV), not meter size. Two systems with the same small leak show different drops depending on how much gas is sitting in them — Ed 4 scales the limit to the real volume.
• Pipework-only retest is now a mandatory follow-on step when appliances are connected. Any perceptible movement on that retest is a fail.
• "Perceptible movement" is now a number, not a judgement call (see below).
• Purge volume is one formula for everything: PV = 1.5 × IV. No more meter-size / pipe-diameter lookup.
• Caravans and leisure accommodation vehicles are now in scope.

Scope — is this the right standard?

All of the following must apply, or you need a different standard (UP/1A, UP/1C, UP/1):

• MOP at ECV outlet ≤ 2 bar (NG and LPG/Air)
• Nominal bore ≤ 35 mm (DN32, R1¼)
• Meter badged capacity ≤ 16 m³/h
• Installation volume ≤ 0.035 m³ per dwelling
• Operating pressure ≤ 21 mbar at meter outlet (NG / LPG/Air) · ≤ 37 mbar at final stage regulator (LPG)

Field note: most domestic jobs fall well under 0.035 m³, but Ed 4 expects you to confirm it rather than assume. As a yardstick, 25 m of 35 mm copper with a U6 is roughly at the limit.

Step 1 — pipework + fittings volume (IVp + IVf)

Length of each run × the figure below, then add the runs together. Fittings are already included at 10%.

Step 2 — meter volume (IVm)

Only include the meter if it sits inside the section you're testing. Use manufacturer data where it's on the badge.

Step 3 — total

IVt = IVp + IVf + IVm — a typical domestic install lands somewhere around 0.005–0.015 m³ (5–15 litres).

Permissible drop — NATURAL GAS (2 minute test)

Permissible drop — LPG

Permissible drop — LPG/Air

"No perceptible movement" — now defined

On the pipework-only retest, any perceptible movement is an automatic fail.

Test sequence (domestic NG)

• Warn the occupier. Ventilate. Appliances off, isolation valves closed.
• Let-by test first — confirms the ECV is sealing. A failed let-by makes everything after it meaningless.
• Manometer on the meter test point. NG: 20–21 mbar. LPG: 37 mbar.
• Stabilise 1 minute.
• Time the test for 2 minutes. Compare the drop against your IV band above.
• Within limit → proceed to the pipework-only retest with appliances isolated. Outside limit → trace and repair, or make safe.

Before 1 October

• Run the IV calculation on two or three recent jobs so the arithmetic becomes automatic.
• Start recording pipe schedules (material, diameter, length). Under Ed 4 that data is reused at every future test and purge, not just at design time.
• If your ACS refresher falls in late 2026, check the provider covers Edition 4 explicitly — not all had updated at time of writing.
• Gas Safe Register agreed not to defect businesses still working to Ed 3 during the transition, but that ends 30 September.

Source: IGEM/UP/1B Edition 4 (Communication 1759), March 2026. Always work from the published standard — this card is a field prompt, not a substitute.

🚨 Unsafe Situations — GIUSP (ID / AR / NCS)

Gas Industry Unsafe Situations Procedure · IGEM/G/11 · what to do when you find it, not just how to find it

Immediately Dangerous (ID)

Definition: if operated or left connected, an immediate danger to life or property.

• Turn off and disconnect with the responsible person's permission.
• Attach a warning label to the appliance / installation.
• Issue a Warning Notice — leave a copy with the responsible person, keep a copy.
• Permission refused? Turn off if you safely can, and report immediately to the gas emergency service. Do not simply walk away.

At Risk (AR)

Definition: one or more recognised faults that could, in future, constitute a danger.

• Turn off with permission, label, and issue a Warning Notice.
• Permission refused → record the refusal on the notice and advise in writing of the risk.
• Not an emergency call-out, but do not sign it off as serviceable.

Not to Current Standards (NCS)

Definition: does not meet today's standards but is not ID or AR.

• Appliance may remain in use. Do not turn it off on NCS grounds alone.
• Advise the responsible person in writing of what and why.
• This is where honest, non-scaremongering advice wins repeat work — explain it as "not how we'd fit it today", not "dangerous".

RIDDOR

As a Gas Safe registered business you have a duty to report a dangerous gas fitting to the HSE where you find a defect that has caused, or could cause, death, loss of consciousness or hospital treatment. Report within 14 days of finding it. This is separate from, and additional to, the Warning Notice.

Common ID triggers on a breakdown call

• Products of combustion spilling into the room — failed spillage test, blocked or disconnected flue.
• Room-sealed case seal missing or damaged.
• Open flue appliance in a bathroom or bedsit without correct protection.
• Gas escape you cannot isolate.
• Flue terminating inside the building, or into a void.
• Boiler running with a bypassed or defeated safety device.

Discipline that protects you

• Never remove a previous engineer's label without your own assessment and record.
• Photograph the defect before you touch it — flue, seal, spillage, label.
• Get a signature on the Warning Notice. If refused, write "refused to sign", time and date it, and photograph it.
• A verbal warning is worth nothing if it ends up in front of an investigator.

Per IGEM/G/11 (GIUSP). Editions and classifications are revised periodically — verify against the current edition before relying on a borderline call.

💧 Water Treatment — BS 7593:2019

The legitimate upsell — and the reason half your callbacks exist

BS 7593:2019 is the code of practice for preparation, commissioning and maintenance of domestic central heating systems. It's the standard behind almost every manufacturer's warranty condition on water quality — Worcester, Vaillant and Ideal all lean on it.

What it requires

• Clean the system before adding anything — chemical clean or power flush depending on condition, per manufacturer guidance.
• Fit an in-line filter on the return. A magnetic filter is the practical choice on any system with steel radiators.
• Dose with inhibitor to the manufacturer's concentration, and record it.
• Test the water annually at service — not "top it up and hope". A test that shows inhibitor has depleted is your evidence for re-dosing.
• Re-dose and record after any work that drains the system, including a single radiator change.

Why it matters commercially

• Manufacturers reject warranty claims on heat exchangers where there's no evidence of cleaning and dosing. Your Benchmark entry and a water test result is that evidence.
• Sludge is the root cause behind a large share of the faults elsewhere in this playbook — pump failures, blocked plate heat exchangers, noisy heat exchangers, low ΔT, radiators cold at the bottom.
• Selling a filter and an annual water test is honest, defensible work. It's a better upsell than anything scripted, because you can show the customer the test strip.

On the job

• Bradford is a hard water area — scale on the plate heat exchanger and DHW side is a recurring pattern locally. Factor scale reducer into combi swap quotes.
• Black water on a drain-down = magnetite. Don't just refill and dose; it needs cleaning first or the inhibitor is wasted.
• Always record the inhibitor brand, product and quantity in the Benchmark log. "Dosed" with no product name is not a record.

🎛️ Boiler Plus, OpenTherm & Smart Controls

Compulsory on every combi swap in England since 2018 — and a huge share of "boiler won't fire" calls

The Boiler Plus requirement (England)

On a gas boiler replacement in England you must fit, as a minimum, time and temperature control — a programmer, a room thermostat and TRVs. On a combi you must additionally fit one of:

• Flue gas heat recovery
• Weather compensation — outdoor sensor varies flow temperature
• Load compensation — room temperature error varies flow temperature
• Smart control with automation and optimisation

Minimum boiler efficiency is ErP 92%. Record which measure you fitted on the Benchmark — it's the first thing an inspector asks about on a combi swap.

Diagnostic reality: it's often the control, not the boiler

• "No heating, no fault code, boiler looks dead" — link out the room stat terminals at the boiler. Fires up? It's the control, wiring or receiver, not the appliance.
• Smart stat batteries and pairing — Hive, Nest, tado and Honeywell receivers drop pairing after a power cut. Customer reports "boiler broken"; it's a re-pair.
• OpenTherm vs volt-free — wiring an OT control into the volt-free terminals (or vice versa) gives you a boiler that either never modulates or never fires. Check which terminals the manufacturer specifies for that control.
• Boiler sat at low output, house never warms — that's compensation working as designed, not a fault. Customer education job, not a parts job.
• Outdoor sensor in direct sun or above a flue terminal gives a false warm reading and underheats the house. North wall, clear of the flue.
• Wireless receiver behind a foil-backed plasterboard wall or in a metal cupboard — intermittent dropouts that look exactly like an intermittent PCB.

Before you condemn a PCB

On any call where the boiler shows no fault and won't fire, prove the demand signal at the boiler terminals with a meter before you quote for a PCB. A wrongly diagnosed PCB is the most expensive callback in this trade and the fastest way to lose a customer to a competitor.

Flow temperature — the free efficiency win

• A condensing boiler only condenses when the return is below roughly 55°C. Most are commissioned at 75–80°C flow and never condense.
• Turning CH flow down to 55–60°C on a correctly sized system typically saves the customer real money and costs you nothing.
• Check radiator sizing first on older properties. If the house won't hold temperature at 60°C, put it back up and price the radiators properly rather than leaving them cold.

Boiler Plus applies in England. Wales, Scotland and Northern Ireland have their own building standards — check the relevant regs before quoting outside England.