Common Worcester Boiler Faults

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Last updated: October 31, 2023

Founded back in 1962, Worcester Bosch is synonymous with quality and is one of the most popular boiler brands in the UK. But even with over 50 years of engineering excellence, their boilers, like other brands, can be susceptible to issues over time.

Being able to troubleshoot common problems with your boiler is key to ensuring your system keeping doing its job. And being prepared can also take the sting out of the moment all householders dread – you suddenly don’t have heating or hot water when you least expect.

To help you understand your Worcester Bosch boiler, we take a look at the most common Worcester boiler faults and what you should do to fix them.

Error Codes for Common Worcester Boiler Faults

In most scenarios, your Worcester boiler should display an error code if a fault is detected.

While their codes can differ depending on the model you have, most Worcester Bosch boilers will have a fault code that starts with either EA or A. To be sure what a displayed fault code means, you should always refer to your boiler’s manual but as a guide, here are the most common issues and associated fault codes you may see:

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Boiler Losing Pressure

When your boiler is working on point, its internal pressure should be in the normal range of between 1 and 1.5 bar. However, low water pressure can be a common issue for Worcester boilers, particularly if they’re on the older side. If your boiler drops below 1 bar, then it’s under pressured and this is not good for your boiler or your home. Low pressure left unresolved will leave you with weak water supplies as well as potentially damaging the internal workings of your boiler. One of the first signs of low pressure can be weak water flow from your tap or even the boiler opting to lockout.

  • Possible causes – one of the most common causes of low pressure in a boiler is a leak somewhere in the whole central system. It could be as simple as a small puncture in a pipe or a loose radiator valve connection, which has allowed water to seep out over time. Other possible causes of low boiler pressure include a faulty or damaged pressure relief valve or if your heating has been switched off for a long period of time.
  • What to do – if your boiler display is indicating low pressure, the first thing to do is re-pressurise the system, especially if the boiler has locked out. By using the filling loop (read your boiler manual on how to do this), you are making a quick fix by bringing the boiler back up to pressure. Now you need to find the reason why the pressure dropped out in the first place. To do this, you need to check the boiler and your central heating system for any signs of leaks, including damp patches or water damage to your floor, walls or nearby furniture. If you do see clear signs that you have a leaking boiler, you need to turn the water supply off and call out a Gas Safe registered engineer who will be able to repair the leak. However, if there’s no signs of leaking and repressurising the boiler still hasn’t worked, you will still need an engineer to assess the problem and make the necessary repairs to any internal components that are damaged.

Boiler Is Leaking

A leaky boiler is not a good thing to have, and you should act quickly if this is the problem with your Worcester boiler as the longer the water is allowed to leak, the greater the damage it will cause, particularly to the delicate electrical parts inside the boiler itself. As well as obvious signs of leaking water, a low pressure reading and even a boiler lockout will be the main indications that you have a leaky problem.

  • Possible causes – degraded components, ruptured pipe joints, loose radiator connectors and blown pump seals are all the likely suspects in the event of a water leak in your boiler or central heating system. Older boilers that have been in use for considerable time are also more prone to leaking due to their age.
  • What to do – if you have a leak, then turn off your water supply so you don’t make the problem any worse. Then look for the source or location of the leak – check your radiators, pipes and the boiler itself so you can pinpoint the problem. To be safe, you are best to call out a heating engineer to fix the leak as it could be to do with internal boiler components which you shouldn’t attempt to fix yourself. Once the leak has been stopped and the cause fixed or replaced, the boiler will need to be repressurised, so it is back working at its best.

Boiler Is Making Noises

The most common noise your Worcester boiler is prone to make is known as ‘kettling’, which sounds like there’s a boiling kettle inside it. Kettling or banging noises can sound a little alarming and while it is not dangerous, such a noisy boiler needs to be addressed if you are to prevent further or more serious damage to your heating system.

  • Possible causes – while most boilers will have a little grumble every now and then, a consistently or suddenly noisy boiler needs further investigation. A kettling sound coming from your boiler is most likely caused by a drop in water pressure, a faulty thermostat or a build-up of limescale, most likely on the heat exchanger. Air trapped inside your boiler, pipework or radiators can also cause banging and kettling sounds.
  • What to do – it’s important that you don’t ignore or ‘learn to live’ with a noisy Worcester boiler, as you could be storing up problems that could be expensive in the long run. If you suspect trapped air, then you can bleed your radiators then re-pressurise the system to see if that silences your noisy boiler. However, if this doesn’t work or you think the noise is being caused by other issues, such as limescale, then you do need to call out a Gas Safe engineer. A heating engineer can accurately diagnose the issue and either perform a powerflush to clean out the system or, if it is a badly limescaled or damaged heat exchanger, replace the affected components.

Boiler Keeps Locking Out

If you see a 227 error code on your Worcester boiler, then this means the boiler has locked out as a safety precaution. Something has triggered this error code and lead the boiler to stop operating in order to prevent any further damage or if it is becoming dangerous. A lockout is one of the most common Worcester Bosch boiler problems and needs further investigation to find out what exactly is going on.

  • Possible causes – A boiler lockout is a vital safeguard that is designed to protect your boiler and can be caused by several key reasons, including high or low pressure, overheating, a blocked flue, a gas supply issue and a problem with the flame sensor.
  • What to do – your boiler’s display may indicate the exact cause of the lockout so refer to your user manual if you see a specific error code. And check the pressure gauge as if it has fallen below 1 bar, you should re-pressurise your boiler to bring it back to the normal zone, then reset the boiler to get it back on track. But if this doesn’t work, or your boiler is indicating another fault, then call out an engineer who can diagnose the cause of the lockout and make any necessary repairs.

Blocked Condensate Pipe

The condensate pipe on your boiler is an essential component as it vents condensation and potentially harmful gases away from your boiler and out of your home. And with many Worcester Bosch boilers, issues with the condensate pipe are pretty common as it has a tendency to get blocked. This is usually during the cold winter months although debris and sludge can also reduce the ability of the condensate pipe to vent properly.

  • Possible causes – cold winter temperatures can freeze the condensate pipe, particularly where it runs outside to the drain. Poor insulation lagging of the condensate pipe can also contribute to it freezing. A frozen condensate pipe will register as a blockage and can cause a boiler lockout. A build-up of debris, dirt and limescale – known as sludge – can also block the pipe, particularly if the boiler is an older model or hasn’t been cleaned or flushed for some time.
  • What to do – if you have an error code that indicates a frozen condensate pipe, it is relatively easy to resolve. All you need it hot – not boiling – water which you need to poor over the frozen pipe to thaw its contents and enable it to flow normally. And, to stop it happening again, check the quality of your lagging and replace if need be. If you suspect other blockages, it’s wise to call out an engineer who can clean out or flush the system if necessary.

Overheating Boiler

An overheating boiler is not an ideal situation to have but with prompt attention, it can be resolved. It is also one of the common Worcester Bosch boiler problems and the main symptom of an overheating boiler is a system lockdown. Today’s boilers will stop working and shutdown if they detect overheating, to prevent the system from becoming unsafe. You may also see the pressure gauge has moved to the high and even critical zone.

  • Possible causes – overheating and increased boiler pressure can be caused by several reasons which can also be identified by error codes on your boiler. Typical causes include a faulty central heating pump, a blocked condensate pipe, a faulty boiler fan or limescale build-up on the boiler’s heat exchanger.
  • What to do – if the condensate pipe is not frozen, then the best course of action for an overheating boiler is to call out a Gas Safe heating engineer who can accurately identify the core problem. If sludge and limescale build-up has caused issues with the heat exchanger, the engineer can perform a powerflush to clean out the system and get it back to its normal operation. And they can replace any faulty components such as the central heating pump. However, if your Worcester boiler is an older model, they may also recommend that it’s time for a new boiler.

No Power To The Boiler

It is the last thing you want, especially on a cold day, but a loss of power is not uncommon in most boilers, including the Worcester Bosch boiler. Or you may experience your boiler unexpectedly or repeatedly turning itself off. If so, you need to get to the cause so you can ensure your home has consistent heat and hot water.

  • Possible causes – the first thing to consider if you experience a total loss of power to your Worcester Bosch boiler is a faulty printed circuit board or PCB, which is the electronic ‘brain’ for your boiler. Or it could be a tripped spur socket or a fault on the residual current device (RCD). And if your boiler is turning itself off, then this could be a low pressure problem, a faulty pump or a pipe blockage that is restricting or preventing water flow to and from the boiler unit.
  • What to do – should you have a power issue with your boiler, the best course of action is to call out an engineer, especially if you suspect that an electrical fault could be to blame. They will be able to do a full diagnostic check on your system to identify the problem and rectify it. Many components can be repaired or replaced, which is usually needed if the PCB is malfunctioning. However, depending on the severity of the issue or the age of your unit, you may need a new boiler.

Related Post: No Power To Your Boiler? Here’s How To Fix It

No Hot Water

Any of the Worcester Bosch boiler range can suffer occasionally from no hot water, which is something you really don’t want to happen. So, if it does, or you find you have lukewarm and less than enthusiastic water coming out of the tap, knowing what to do will ensure that lovely hot water is back on track.

  • Possible causes – as a common issue, there are several main causes behind a lack of hot water so whittling it down will help to save you time and possibly money. Top of the usual suspects list is a faulty diverter valve, which directs water from the heating to the taps, eg. when you need to run a bath or turn on your shower. This is the likely cause if your heating still works, but the hot taps don’t. Alternatively, there could be a faulty printed circuit board (PCB), perished diaphragms, thermostat issues, low water levels and issues with a locked or seized heating pump.
  • What to do – while you may be able to diagnose the issue yourself, you will need to call out an engineer as many of the issues behind a lack of hot water are relating to internal components or electrical faults. Parts, such as the diverter valve or heating pump, can be replaced and the engineer can also clean out the system if build-up is causing a hot water problem.

Radiators Not Heating Up

A problem with the way your radiators heat up can affect Worcester Bosch boiler systems and it is an issue which, in most cases, can be easily rectified. You may experience a full cold radiator system or just one or two of your radiators failing to heat. Alternatively, you may have cold spots in your radiators or radiators that don’t get hot at the top.

  • Possible causes – Radiators that heat up in a patchy way, or don’t heat up at all are most likely affected by trapped air or a build-up of sludge in the system. These will both prevent the hot water pumped from your boiler getting completely around your radiators or stopping them from fully heating up.
  • What to do – The easiest way to get rid of trapped air is to bleed your radiators, which is something you can do yourself. You will need a radiator bleed key and a little patience as well as following your manufacturer’s instructions if you haven’t bled radiators before. However, if you don’t want to attempt bleeding radiators yourself, an engineer will be able to do it for you. They will also be able to clear sludge and limescale blockages, if this is the problem, with a powerflush to get everything happily flowing again.

Which Worcester Boiler Problems Need a Heating Engineer?

Being able to identify issues with your Worcester Bosch boiler makes good DIY sense but you shouldn’t attempt to fix all of these common problems yourself. Some faults need the expert attention of a heating engineer as DIY can cause more problems and even invalidate your boiler warranty.

To help you make the right decision when it comes to correcting your Worcester boiler problems, here’s a list of the common faults and what you should – and shouldn’t – do.

Issue Likely cause Call an engineer?

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How do I reset my Worcester boiler?

You will need to reset your boiler if the error code needs to be removed, for example in the case of a boiler lockdown. It is also a good idea to reset your boiler after any faults have been repaired.

The actual process to reset your Worcester Bosch boiler may differ slightly from model to model so always refer to your instruction manual. However, as a general guide, you need to press the boiler’s reset button for several seconds until the fault indicator stops flashing and the display is cleared. You will also know the reset has worked as you will hear the boiler restart and a green light will return. However, if the reset doesn’t work, don’t keep pressing the reset button but call out a heating engineer.

How Do I Fix the Pressure on my Worcester boiler?

You can bring your boiler’s pressure back to the normal zone by using the filling loop, which can be either internal or external depending on your Worcester boiler model. To re-pressurise the boiler, follow the instructions in your manual until the pressure is between 1 and 1.5 bar (or as indicated). However, if the pressure keeps dropping, even after you have repressurised the boiler, or you know you have a water leak, always call out a Gas Safe engineer so the problem can be successfully resolved.


  1. Find answers to your questions online – Worcester-Bosch