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Common Worcester Bosch Boiler Problems


Worcester Bosch has been a trusted boiler company in the UK for more than five decades. It was founded in 1962 and has undergone some transformations over the years into the market leader in the UK boiler industry.

But though Worcester Bosch boilers are reliable and efficient, they can develop problems. These problems can be worrying and stressful. Because of this, Worcester Bosch built-in fault codes to help you approach the boiler problems logically, decide if it’s urgent and solve it without breaking a sweat.

Below are all the boiler problems along with their fault codes for easy troubleshooting.

Blocked Condensate pipe

Condensing boilers all have condensate pipes. These pipes serve as an escape route for harmful gases and wastewater produced when the boiler is running. It’s easy to identify these pipes since they are the only plastic pipe connecting to the boiler. They are usually shorter than 3m and are insulated to minimize the chances of freezing during winter.

But from time to time, the condensate pipes get blocked. When this happens, the boiler will make gurgling sounds when it’s powering up or lockout. Also, the Worcester Bosch boiler will display an EA225 fault code.


As mentioned above, cold weather is the most common culprit of condensate pipe blockage. This is because the pipes are installed outside the property.

To get rid of the blockage (the ice frozen within the pipe), pour warm water over the pipe.  Do not use boiling water as this could deform the plastic pipe in the process. To prevent the blockage from reoccurring, insulate the pipe with lagging.

No hot water

To make a proper diagnosis of the boiler problem, you need to determine which of the below combination of problems applies to you:

  • No heating and no hot water
  • The heating works, but there’s no hot water
  • The cold water works but there’s no hot water
  • Only the shower doesn’t have hot water


If the boiler is not heating and there’s no hot water, it might be a power problem. If the boiler is turned on, but the control panel is blank, check the fuse. You should also ensure the fuse box is not tripped and that you have paid your electricity bill. Once you fix these problems, reset the boiler, and it should run normally.

If the power is on, but you still don’t have hot water or heating, the heating pump might be the culprit. To ascertain the problem, feel the temperature of the return pipes. If they aren’t warm, the heating pump is faulty.

Heating pump faults are caused by a myriad of things, including dirt blockage, air build-up, incorrect installation, incorrect speed settings, no power, and pump leaks. Luckily, the solutions are easy fixes including adjusting the pump speed, cleaning the pipe, and bleeding the pump.

We also suggest checking if the pilot light is off. If it’s off, turn off the gas and check if you have a gas supply. If you do, the light was probably blown out by a draft. In this case, re-igniting the pilot light will fix your problem.

On the other hand, if you don’t have hot water but the heating works, it’s a possible sign of a faulty diverter valve. You’ll need to replace the diverter valve to fix the problem.

And lastly, if you don’t have hot water only in the shower, the problem could be a stuck or broken mixing valve. The good thing is that mixing valves are cheap to replace.

Boiler is leaking

If the Worcester Bosch boiler leaks, it will result in a low pressure, and the boiler will lockout. Most often than not, the cause of a leaking boiler is a blown pump seal. This occurs when the seal gets worn out over time and succumbs to flow rate pressure.

The Worcester boiler picks up on this fault and displays either an EA338 or an A281 fault code.


Boiler leaks are usually serious, but not always. Before paying a Gas Safe engineer £100, determine the cause of the leak.

  • Are the seals worn out and degraded? If yes, the pump unit should be replaced.
  • Is the boiler pressure higher than 2.0 bar, and is the pressure relief valve blown? If yes, a new pressure relief valve is needed.
  • Is the pipework joints leaking? This is easily fixed with a heating system sealant. But if the pipework is improperly installed, call in a Gas Safe engineer.
  • Has it rained heavily recently? Rainwater could be the cause of the leak which means, the boiler flue is improperly installed. Get a Gas Safe engineer on this immediately.

NB: replacing an entire pump unit is faster than replacing the seals. Also, there isn’t a huge price difference between the two options. And lastly, remember to reset boiler pressure to the green zone 1.2 bar once the boiler leak is fixed.

Boiler keeps locking out

Whenever the Worcester boiler has a fault, it will lockout to guarantee safety. The lockout prevents it from running and also saves the system from further damage. There are numerous reasons why a boiler can lockout. These include:

  • Blocked condensate pipe
  • Blocked flue
  • Faulty flame sensor detector
  • Insufficient gas supply
  • Low or high boiler pressure

These are some common causes. Luckily, Worcester Bosch boilers display fault codes specific to the cause. The code could be EA227 denoting no flame detection.


To solve the problem, you need to diagnose the problem causing the lockout first. Depending on the cause, you can either DIY or hire a professional engineer.

No power to the boiler

If your boiler is not receiving any power, don’t freak out. This can be caused by a tripped RCD unit, faulty PCB, fuse blown in the spur. If it’s a problem with the main power, you’ll get an FD 231 fault code.


Your next course of action depends on the problem cause. You’ll have to inspect the fuse, the RCD, switches, PCB, and spur to ensure they are in good working condition. Luckily, if any of them is faulty, repair or replacement is easy and affordable.

But before all the above troubleshooting, your first step should be to ensure there’s power in the house.

The boiler is making banging noises

A41 is the fault code commonly related to noisy boilers. Usually, boiler noises are caused by:

  • A faulty heat exchanger.
  • An airlock in the boiler pump.


An airlock in the central heating system is easily fixed by bleeding the pump. As for a faulty heat exchanger, you can attempt a Powerflush to remove limescale build-up. If that doesn’t work you should consider replacing the heat exchanger. But unfortunately, they aren’t cheap. As such, if your boiler is past its ten-year mark (it’s no longer under warranty), you should consider buying a new boiler instead.

Worcester boiler overheating

Some common causes of Worcester boiler overheating include:

  • Faulty pump
  • Problematic fan
  • Blocked or frozen condensate pipe
  • Limescale build-up in the heat exchanger

As such, the most common fault codes relating to overheating include E5 218, E9 219, E5 332, E9 224, and D1 286.


Unless it’s an issue of a frozen/blocked condensate pipe that you can fix yourself, you should always call a Gas Safe engineer to handle overheating problems. If sludge and limescale have built up within the system, the engineer will Powerflush the system. He’ll also fit a magnetic filter to protect the system from future sludge blockage.

When the problem is fixed, reset the boiler.

Boiler pressure

Worcester boilers slowly lose pressure over time. However, a boiler cannot function with low boiler pressure. Often, to prevent further damage, your boiler will lockout. EA 338 is the common fault code related to low boiler pressure.


Aside from the fault code, diagnosing low boiler pressure is easy –inspect the boiler pressure gauge. The gauge should read between 1 bar and 1.5 bar.

Adding water to the system through the external filling loop should fix the problem. But if it doesn’t, it means you have a leak. In such cases, you should turn off the water supply and get a Gas Safe engineer to locate and seal the leak.

Other fault codes and troubleshooting

Fault code 9A 362 – Wrong heat control module installed.

How to fix: Call a Gas Safe engineer to replace or repair the heat control module.

Fault code C6 215 – Boiler fan is running unusually fast.

How to fix: Call a Gas Safe engineer to diagnose the problem cause, repair, or replace the fan.

Fault code B7 257 – Faulty control board.

How to fix: Replace the control board.

Fault code C7 217 – Blocked airflow.

How to fix: Unblock the system or replace the fan.

Fault code D1 241 – damaged or disconnected return sensor.

How to fix: Professional diagnosis required

How to improve your boiler’s life

Worcester boiler guarantee

First, we must explain the difference between a warranty and guarantee. Typically, warranties include payment of premiums (much like insurance), and guarantees are free. Guarantees are legally binding for manufacturers and are designed to improve customer laws.

Under UK law, all boilers should have two years guarantee. However, Worcester Bosch offers five years as their standard guarantee. If you meet specific requirements like hiring a Worcester Bosch Accredited installer, the guarantee increases to up to 10 years.

Worcester Bosch boiler cover

Worcester helps to improve the boiler lifespan by providing warranties/covers for specific boiler parts. While manufacturers can charge for a call out, Worcester Bosch doesn’t charge provided you service the boiler annually.

To improve boiler life even further, Worcester Bosch offers warranties and covers for Worcester Bosch parts installed along with the new Worcester boiler. For instance, if you have a Worcester Bosch filter installed, you’ll receive a maximum of 10 years’ cover on the items.

Worcester boiler service

One of the conditions of maintaining a Worcester boiler guarantee is conducting annual boiler services. These services will ensure boiler parts are working efficiently and catch faults at their early stages.

If faults are caught during annual servicing, Worcester will repair them up to £1,500.

What Next?

If after the above fixes you still encounter boiler problems, you should consider a boiler replacement. A new boiler will save you as much as £300 annually in energy bills.

And we are more than happy to offer free quotations from Gas Safe engineers in the UK.

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