Worcester Bosch Support: 0330 123 3366

Worcester Bosch technical support numbers

Worcester Bosch publishes its numbers department by department, so the fastest call depends on what you are ringing about. The line most homeowners want is the Consumer Technical Helpline. If your question is about an appointment, a guarantee or a manual rather than a fault, one of the other numbers gets you to the right team first time. Worcester Bosch publishes one set of opening hours for all these lines: Monday to Friday 7.00am to 6.00pm, Saturday 8.00am to 5.00pm, Sunday 9.00am to 12.00pm.

Numbers and opening hours as listed by Worcester Bosch on its own Important Contacts page.

Smart Plan is independent and is not affiliated with Worcester Bosch. The numbers, hours and fault-code wording on this page are Worcester Bosch’s own.

There is a written route too. Worcester Bosch's customer support hub carries a troubleshooting tool, the FAQs, how-to videos, free manual downloads and, on its troubleshooting page, a live chat with its online customer care team, started from the icon in the bottom right-hand corner. If you want every route in one place, including the online service and cancellation forms, we keep a fuller list on our Worcester Bosch contact page.

Read the code on the display before you call

A Worcester Bosch technical adviser will ask what the boiler is showing, so have the code in front of you before you ring. Having it in front of you turns a long diagnostic conversation into a short one, and it often tells you straight away whether this is something you can clear yourself.

Older Greenstar boilers show a letter code with the fault indicator LED flashing. Worcester Bosch’s Greenstar CDi Classic documentation describes the fault being shown two ways at once: a letter code in the display and a flashing fault indicator LED. Newer models such as the Greenstar 8000 show a three or four digit number with a category letter beside it in the fault code table.

What the category letter means

Worcester Bosch’s Greenstar 8000 documentation sorts every code into four groups, and the group tells you what to expect next:

• O, operating codes - these "indicate the operating conditions in normal operation". Not a fault at all.
• B, blocking faults - "Blocking faults result in the heating system being shut down temporarily. The heating system restarts automatically as soon as the blocking fault is removed."
• V, locking faults - "Locking faults result in the heating system being shut down, and the system can only be restarted after a reset."
• W, maintenance codes - a service reminder rather than a breakdown.

So a B code that keeps coming back is telling you the underlying cause is still there, and a V code will not clear on its own no matter how long you wait.

Common codes and what Worcester Bosch says they mean

Fault-code meanings summarised in our own words from Worcester Bosch’s published documentation for the Greenstar CDi Classic and Greenstar 8000 ranges. Check the current wording for your model on Worcester Bosch’s own troubleshooting pages. Our full list is at Worcester Bosch boiler fault codes.

Resetting, and when to stop

The CDi Classic manual gives the reset as: "Press the reset button for 3 seconds and release it. After releasing the appliance re-starts." Worcester Bosch's frozen condensate advice uses a slightly longer press on newer models, so check the user instructions for your model.

One reset is a reasonable thing to try. Repeated resets are not. A locking fault exists because a safety device did its job, and holding the reset button until the boiler stays on is a way of ignoring the reason it locked out. If it locks out twice, book an engineer.

Boiler pressure is too low or too high

A Worcester Bosch combi or system boiler runs on a sealed, pressurised circuit, so the pressure has to sit inside a set band for water to move round the house properly. Worcester Bosch’s Greenstar 8000 documentation gives the band as 1 bar minimum charge pressure when the system is cold and 1 to 1.5 bar optimal charge pressure. The CDi Classic fault checks ask the same question a different way: is the heating pressure between 1 and 2 bar?

The instruction for a low reading is equally specific. If the pressure reads below 1 bar with the system cold, top the water up until the gauge sits between 1 bar and 1.5 bar. Your filling loop will not look identical to everyone else's, so follow the user instructions for your model rather than a generic video.

Here is the part that matters more than the topping up. Pressure does not disappear on its own. If you are refilling every few weeks, something is letting water out, and the boiler will tell you: code H07 / 2971 means the system pressure is too low and 2970 means it is dropping too quickly. Look for damp patches around radiator valves, towel rails and pipework, and read our guide on why a boiler keeps losing pressure before you top it up again.

A reading that climbs well above the band is usually too much water in the system or an expansion vessel that has lost its charge. Bleeding a radiator releases the excess in the short term. A vessel recharge is an engineer's job.

Boiler is making unusual noises

A quiet hum is normal. Anything louder is worth listening to properly, because the sound narrows down the cause.

Banging on ignition

The boiler tries to light, does not catch first time, and the gas that has built up ignites in one go. Worcester Bosch lists harsh or poor ignition in its own table of faults that do not show a code. This one is not a homeowner job at any level: the burner, the electrodes and the gas valve are all gas components, and only a Gas Safe registered engineer may touch them.

Rattling or humming from inside the case

Usually the pump, and often air. Worcester Bosch’s code 305 covers a pump that is stuck or running in air. Do not open the boiler casing to get at the pump. Removing the case on a gas appliance is engineer work, and Worcester Bosch is explicit elsewhere that you should never remove screws to get at parts of the boiler. What you can safely do is check the pressure gauge and bleed your radiators.

Kettling, a boiling or whistling sound

Limescale and sludge building up inside the heat exchanger cause hot spots, and the water flashes to steam against them. Worcester Bosch lists excessive burner noise, rumbling and flow noises among its undisplayed faults. Kettling gets worse, not better, and a boiler that is kettling loudly is heading for a heat exchanger bill, so it is worth booking rather than living with.

No heating, no hot water or both

Which one you have lost is the diagnosis, so check both before you ring anybody.

Neither works. Start with the free checks: is the programmer calling for heat, is the room thermostat set above room temperature, is the pressure gauge inside the band, and is there a code on the display. On a system with a motorised valve, a valve stuck in one position will stop hot water reaching part of the system.

One works and the other does not. On a combi that usually points at the diverter valve, the component that decides whether hot water goes to the taps or the radiators. It gives priority to the taps, and when they are off the heat goes to the radiators instead. When it sticks, you get one and not the other.

Valves are not a homeowner repair. Book it, and quote the code if there is one. Our step by step pages on no heating and no hot water run through the safe checks in order.

Radiators are cold

Cold at the top, warm at the bottom. Air trapped in the radiator. Bleed it, then check the pressure gauge afterwards, because bleeding lets pressure out and you may need to top back up to between 1 and 1.5 bar.

Cold at the bottom, warm at the top. Sludge sitting in the bottom of the radiator. Bleeding will not shift it. It needs a chemical or power flush by an engineer, and a magnetic filter afterwards to stop it coming back.

Every radiator lukewarm. Look at the pump and the circulation rather than the radiators. Code 305, a pump stuck or running in air, and code A1, a pump that has run dry, both describe circulation failing rather than heat failing.

Boiler leaking

Water coming out of a Worcester Bosch boiler is never something to monitor for a week. Turn the boiler off, put a container under the drip, and book an engineer.

The common causes are a failed seal, a corroded pipe joint, a pressure relief valve discharging because the pressure has been too high, or corrosion in the heat exchanger. Only the last of those is expensive, and only an engineer can tell you which one you have. Water and electrics in the same box is also the reason not to keep running it: leave it off until someone has looked. There is more detail on our boiler leak repair page.

Frozen condensate pipe

This is the one winter fault most people genuinely can fix themselves, and Worcester Bosch says so on its own advice page. The condensate pipe carries acidic water away from the boiler, it is thin, and where it runs outside it can freeze. Worcester Bosch’s own advice is that frozen condensate blocks the condensate drain pipe and stops the boiler running.

The symptoms Worcester Bosch names are a gurgling noise from the boiler and, on a digital display, an EA error code. Its own advice runs to three steps, summarised here in our words:

1. Find the outdoor pipe connected to your boiler, normally white plastic, running to an external drain.
2. Only if you can reach it safely, pour warm water along the pipe. Warm, not boiling: boiling water can crack the pipe.
3. Reset the boiler once the pipe has defrosted.

Take the "only if you can reach it safely" part seriously. If the pipe is up a ladder, on a flat roof, or across ice, that is not a job to attempt alone. If it refreezes every cold snap, the fix is insulation or a rerun of the pipework, which an engineer can quote for.

Pilot light going out

Worth knowing before you go looking: modern Worcester Bosch Greenstar boilers do not have a standing pilot light. The manuals describe a spark electrode that lights the burner on demand and a flame sense electrode that confirms it lit. If your boiler is not lighting, the code you will usually see is EA or 227, which Worcester Bosch defines as no flame signal after ignition.

Its own fault table lists the causes an engineer works through, and every one of them is gas or combustion work: the gas supply and the gas valve, the air intake, a blocked or restricted condensate trap or flue, a blocked heat exchanger, a damaged burner, and the spark and flame sense electrodes. Note that a frozen condensate pipe appears on that list, which is why the section above is worth trying first in cold weather.

An older boiler with a genuine standing pilot that keeps going out may have a failing thermocouple. That is a gas safety device, so it is a Gas Safe registered engineer's job and nobody else's. If you can smell gas at any point, stop and call the National Gas Emergency Service on 0800 111 999.

Thermostat is not responding

A dead thermostat looks exactly like a dead boiler from the hallway, and it is far cheaper to rule out first.

Set the target temperature at least two degrees above the current room temperature and listen for the boiler to fire. If nothing happens, change the batteries in the control, then check that a wireless control is still paired to its receiver, because a control that has lost its pairing behaves exactly like a dead boiler. A control that has drifted out of range or been moved to a new shelf can do the same thing.

Our Worcester Bosch thermostat troubleshooting guide works through the wired, wireless and app controlled versions separately, and how to set a Worcester thermostat covers the programming itself.

Who actually fixes it: Worcester Bosch or an independent engineer

This decides your next phone call, so it is worth two minutes.

If the boiler is still in guarantee, use Worcester Bosch. They arrange and pay for the repair, and you will not get that from anyone else. Check the expiry date first with the free serial number checker, which we walk through on our Worcester Bosch guarantee check page. Worcester Bosch sets its own guarantee conditions, including servicing requirements, in its guarantee terms and conditions, so check those before you assume you are out of guarantee.

If it is out of guarantee, the choice is yours. Worcester Bosch will still send an engineer as a one-off paid repair, and so will any Gas Safe registered engineer. From that point you are either paying per breakdown or putting cover in place before the next one.

If the boiler is under guarantee, none of that applies today. Ring Worcester Bosch on 0330 123 3366, quote the code on the display, and let them arrange it.