Eco Happy (Solar Expert)

Published February 8, 2024

Understanding the intricacies of your Worcester Bosch boiler isn’t just for engineers and technicians.

Familiarity with the ins and outs of your heating system, specifically your boiler’s error codes, is an invaluable skill. It allows you to identify and potentially rectify minor issues before they become major problems.

For those seeking to take control of their home heating systems, this blog post will serve as your guide through the labyrinth of Worcester boiler fault codes, their meanings, and how to diagnose and fix them. Let’s dive in!

Worcester Boiler Error Codes – Summary

  • Worcester Bosch boilers come with error codes that can help users identify and diagnose various issues.
  • Troubleshooting techniques involve resetting the boiler, inspecting for visible issues, verifying the boiler pressure, and examining for any signs of leaks.
  • Professional installation or replacement of an older Worcester Bosch model is recommended to improve energy efficiency and reduce heating costs.

Worcester Bosch Boiler Error Codes

So, you have your Worcester Bosch boiler installed in your home, and something goes wrong, causing an error code to show up. You are now probably wondering what it means and what you should do next.

Well, much like other appliances, Worcester Bosch boilers come equipped with a built-in system of error codes that aid users in pinpointing and diagnosing problems.

These alphanumeric codes flash on the boiler’s display panel whenever the boiler encounters a fault, a veritable language of its own that, once understood, can be a powerful tool for homeowners.

The error codes cover a wide range of problems, from issues with the heat exchanger temperature sensor to problems with the flow temperature sensor. These codes range from the fairly straightforward SE Code, which signifies that the boiler requires service after running for 2324 hours, to more complex codes like those beginning with the letter ‘H’.

These ‘H’ codes serve as alerts that the boiler should be inspected by a qualified engineer, but they do not prevent the boiler from functioning. Even when the issue lies with a seemingly complex component like a defective module HCM, these codes can be a great aid in troubleshooting.

Each error code serves a unique purpose and helps identify the precise error occurring within the boiler. For instance, the Worcester Bosch CDI Highflow boiler has common error codes that cover a variety of issues, such as pump dry run detection, flame not detected, and problems with the flow temperature sensor.

While familiarity with error codes is important, knowing the appropriate response is of equal significance. In the event of a fault code, the boiler can be reset by holding the clear ‘reset’ button for 3 seconds or adjusting the light at the end of the temperature dial until it reaches the ‘reset’ position and maintaining it there for 3 seconds.

This process should be followed even if the issue is related to not using the flow temperature sensor correctly.

Guide to Diagnosing Worcester Bosch Fault Codes

Now that you have gained more of an understanding of the basic Worcester Bosch boiler error codes, the subsequent step involves learning the techniques for diagnosing these faults.

The boiler uses visual cues such as flashing lights to indicate faults. Here are some common error codes and their meanings:

  • Long flashes: issues with the minimum burner load
  • Short flashes: issues with the maximum burner load
  • Alternating long and short flashes: issues with the fan speed
  • Rapid flashing: issues with the ignition

By understanding these visual cues, you can diagnose and troubleshoot the faults in your Worcester Bosch boiler.

The boiler error codes come in two varieties: blocking error codes and locking error codes. Blocking error codes refer to temporary issues that cause the boiler to cease functioning without showing a specific fault code.

On the other hand, locking errors are identified by a flashing fault code and a triangle symbol. A boiler reset is required once the problem has been addressed. These issues can include problems with the modulating gas valve.

If a blocking error occurs, you can access the cause code by pressing the return button. This can help identify the reason for the error and provide valuable information for troubleshooting. If a locking error occurs, the screen should flash the cause error code intermittently. This will help identify and address the issue effectively.

These cause codes can help identify issues with components such as the flow and safety sensor, and it’s important to check pressure sensor connection as well. To clear a locking error, one must press the Worcester boiler reset button for 3 seconds.

The appearance of the error code ‘hot water temperature sensor faulty’ signifies a fault in the hot water temperature sensor. In some cases, the pressure sensor might also be involved in the error detection process.

Addressing Blocking Worcester Error Codes

Blocking error codes typically signal transient issues that can often be resolved once the cause is identified and dealt with. These errors can stem from a variety of factors, such as:

  • Fan speed errors
  • Heat control module (HCM) issues, including when the module HCM is defective
  • Absence of a flame signal often caused by blockages or internal leaks
  • Blocked pumps

One common cause of blocking errors is a blocked condensate pipe, which can be identified by listening for gurgling noises or unusual sounds from the flue. Another potential issue could be a gas valve leak. To troubleshoot these issues, you can:

  • Gently remove visible blockages
  • Use a pipe brush or compressed air to dislodge stubborn debris
  • Flush the system with distilled vinegar to remove mould or algae
  • If the blockage is stubborn, it may be necessary to undo the white nut below the solvent weld elbow to clear trapped water.

In some cases, the condensate pipe might be frozen, causing a blockage. In such situations, you can pour warm water over the external part of the pipe or apply heat using a hot water bottle until the blockage is melted. If these methods do not resolve the blockage, it is advisable to seek professional assistance.

To resolve a blocked condensate pipe, you’ll need tools like a pipe brush, compressed air for persistent blockages, and possibly a hot water bottle to thaw any frozen blockages in the pipe.

Fixing Locking Worcester Bosch Fault Codes

Unlike blocking errors, locking fault codes serve as indicators of more chronic and grave issues impacting the boiler’s functionality.

These often necessitate professional assistance for resolution. The ‘Flame not detected’ code indicates that the boiler’s sensors are not detecting a flame when it should be present, potentially pointing to an issue with the ignition.

A ‘Burner control error’ signifies a malfunction in the control mechanism that manages the burner’s operation, potentially impacting the boiler’s capacity to heat water and the home.

Thermistor-related locking fault codes like ‘DHW NTC defect’ and ‘Tank NTC defect’ signify a malfunction with the domestic hot water thermistor and the thermistor in the storage tank, respectively.

These issues can affect the boiler’s ability to store hot water at the proper temperature and may lead to temperature detection and regulation issues, potentially requiring a safety temperature limiter to prevent further complications.

Other locking codes, like ‘Condensate pump failure’ or ‘EMS communication error’, indicate more complex issues. The former signifies that the pump responsible for removing condensate from the boiler is not functioning properly, potentially leading to water damage if not resolved.

The latter is an issue with the boiler’s communication system, which may hinder efficient operation and necessitate more intricate troubleshooting.

Worcester Bosch Error Code Breakdown

Having developed a fundamental understanding of Worcester Bosch boiler error codes and their diagnosis, we can now examine some of the most frequently occurring error codes and their implications in more detail.

The EA error code can indicate various issues, such as:

  • Insufficient gas supply
  • Malfunctioning ignition electrode or lead
  • Problem with the flame sensor
  • Abnormal flow temperature rise

When this error code is displayed, it is advisable to contact a qualified gas-safe engineer to address the issue. It is vital not to reset the boiler when this error code is present, as doing so may lead to additional damage.

Another common error code is the Worcester C6 fault code, which indicates that the boiler fan is not functioning properly, potentially necessitating a fan replacement or further assessment by a qualified professional.

Worcester EA 227 Error – Frozen Condensate Pipe

An EA 227 error code is a clear sign of a frozen condensate pipe. This might seem daunting at first but don’t worry. You can take steps to resolve this issue.

You can thaw the pipe using warm water or insulation. Yes, you read that correctly! Homeowners can address the frozen condensate pipe issue themselves by following the provided guide.

Thawing out your frozen condensate pipe can be done via two different methods: pouring warm water over the pipe or using a hot water bottle. For the warm water, you should heat some water up in the kettle, but make sure it isn’t boiling, as this could damage the pipe.

Carefully pour the warm water over the frozen condensate pipe to unfreeze it, then restart your boiler.

When using a hot water bottle, fill the bottle with hot water and hold the bottle up against the frozen pipe. This should slowly unfreeze or unclog the condensate pipe without damaging it.

Worcester Bosch A21 Fault – Faulty Thermostat

An A21 fault code is another common error that homeowners might encounter. This code signifies a loss of radio frequency (RF) signal between the thermostat and the boiler, commonly associated with a thermostat issue.

Indications of a faulty thermostat in a Worcester Bosch boiler may include:

  • Atypical noises such as banging
  • Unresponsiveness to thermostat settings
  • Inaccurate temperature readings
  • Water boiling in the expansion tank

A malfunctioning flue gas thermostat can disrupt the communication between the boiler and thermostat, leading to inadequate temperature regulation.

This can result in uneven heating or cooling within the home, causing discomfort and potential energy inefficiency.

Worcester C6 Fault Code – Boiler Fan Not Working

The C6 fault code signifies an anomaly related to the boiler fan, such as:

  • irregular fan speed, either being too low or too high
  • abnormally low fan speed
  • loose connections
  • damages from leaks
  • a non-responsive fan
  • issues with the circuit board

These are indications of a malfunctioning Worcester Bosch boiler fan, which could be related to a gas valve relay issue.

A malfunctioning fan can cause potential boiler malfunction or failure, reduced energy efficiency, and safety hazards such as the accumulation of carbon monoxide. If you suspect a fan issue, there are several troubleshooting steps you can take:

  1. Inspect the PCB for moisture.
  2. Listen to the fan during startup.
  3. Examine any loose connections.
  4. Inspect for damage caused by leaks.
  5. Check for faults in the fan and control board.

If the issue persists, it is advisable to seek assistance from a professional technician. If a fan replacement is required, there are steps you can follow:

  1. Turn off the power.
  2. Remove the front cover.
  3. Disconnect electrical connections.
  4. Remove the fan.
  5. Install the new fan by reversing these steps.

Preventing Worcester Fault Codes

Hopefully, with the aid of this guide, your Worcester Boiler problems have been solved, and your boiler is back up and running. That means you can look to prevent these issues from happening in the future.

The old adage ‘prevention is better than cure’ rings true when it comes to Worcester Bosch boilers. Regular maintenance and servicing of the boiler can help prevent the occurrence of fault codes.

Routine servicing contributes to the prevention of fault codes by maintaining the boiler in optimal condition.

Through maintenance checks, potential issues can be identified and resolved before they lead to fault codes, ensuring the proper functioning of the boiler.

However, it’s not just about regular servicing. There are signs that warrant the involvement of a professional installer for a Worcester Bosch boiler. These include:

  • frequent breakdowns
  • unusual noises
  • visible leaks or water damage
  • inconsistent heating
  • rising energy bills
  • recurring fault codes on the display

Additional preventive measures to mitigate Worcester boiler error codes involve:

  • Implementing regular boiler maintenance
  • Ensuring system cleanliness
  • Monitoring water pressure
  • Bleeding the radiators
  • Checking for leaks.

Worcester Bosch Boiler Service

Servicing your Worcester Bosch boiler annually is a great preventive measure that can help extend its lifespan and maintain its optimal condition.

Regular maintenance of a Worcester Bosch boiler offers various advantages, such as increased energy efficiency, prolonged boiler lifespan, and improved safety.

Servicing a Worcester Bosch boiler typically involves a series of tasks, including:

  • Cleaning and inspecting components
  • Checking for faults or leaks
  • Testing performance
  • Ensuring safe operation

A typical service will involve checking the boiler in accordance with the manufacturer’s instructions and replacing any parts that have failed due to manufacturing issues.

Call a Professional Installer

Though homeowners can tackle some minor issues, there are instances when they must call upon a professional installer. Engaging a professional for Worcester Bosch boiler repairs is essential due to their specialised expertise and ability to accurately diagnose and resolve boiler issues. DIY Worcester Bosch boiler repairs can present various risks, such as:

  • safety hazards
  • warranty nullification
  • substandard repairs
  • the potential for carbon monoxide exposure

To verify the qualifications of the installer, it is recommended to check for Worcester Bosch accreditation, which signifies that they have completed expansive training at Worcester Bosch HQ.

The process for locating a certified Worcester Bosch installer near you involves visiting the Worcester Bosch website and utilising their search feature to find installers in your area.

The typical cost of hiring a professional Worcester Bosch installer is approximately £2,200.

Troubleshooting Techniques for Worcester Faults

A lot of the issues can actually be solved by you rather than having to call out an engineer every single time a fault code is displayed.

Homeowners can deploy a range of troubleshooting techniques to tackle Worcester faults, which include:

  • Resetting the boiler
  • Inspecting for visible issues
  • Verifying the boiler pressure
  • Examining for any signs of leaks

To reset a Worcester Bosch boiler, it is necessary to press and hold the reset button located on the control panel for a duration of approximately 3 to 5 seconds.

Typical reasons for malfunctions in Worcester Bosch boilers include issues with the diverter valve, condensate or flue pipe blockages, problems with fuel supply, irregular boiler pressure, and dysfunction of the fan or pump.

To identify these issues, it is recommended to check the availability of hot water, inspect the condensate or flue pipes, ensure the fuel supply is consistent, monitor the boiler pressure, and be mindful of unusual noises or signs of overheating.

Worcester Bosch Boiler Replacement

At times, despite all your best attempts, a Worcester Bosch boiler might still require replacement. Indications that a Worcester Bosch boiler may require replacement include:

  • Overheating
  • Unusual noises (such as hissing, banging, or whistling)
  • Extended heating times for water or radiators
  • Leaks
  • Frequent breakdowns

Worcester Bosch boilers typically have a lifespan of 12 to 15 years before requiring replacement.

Upgrading a Worcester Bosch boiler can potentially enhance efficiency by:

  • Replacing an older, less efficient model with a newer, more efficient one
  • Newer A-rated condensing boilers can provide efficiency ratings as high as 92%
  • Resulting in reduced energy consumption and heating costs
  • The replacement of an older Worcester Bosch boiler with a new one has the potential to yield energy cost savings of approximately 20-30%.

When to Upgrade Your Worcester Boiler

It’s vital to recognise the right time to upgrade your Worcester boiler. Indications that a Worcester Bosch boiler may require replacement consist of:

  • frequent breakdowns and the necessity for frequent repairs
  • unusual sounds emanating from the boiler
  • water leakage from the boiler
  • the boiler surpassing 10 years of age
  • escalating heating expenses
  • noisy boiler or radiators

Worcester Bosch boilers generally have a lifespan of 12 to 15 years before requiring replacement.

Potential factors that may necessitate a prompt upgrade of a Worcester Bosch boiler include changes in water consumption, a faulty diverter valve, and common boiler issues like frequent shutdowns or a malfunctioning thermostat.

Replacing an older Worcester Bosch boiler model with a newer one can yield significant benefits such as enhanced energy efficiency, decreased heating expenses, and a prolonged lifespan of the boiler.

The financial outlay for replacing a Worcester Bosch boiler may vary between £1,500 and £4,500, contingent upon the specific requirements of the task and any supplementary labour or add-ons.

Worcester Boiler Faults – Final Thoughts

We’ve covered a lot of ground in this guide, from understanding Worcester Bosch boiler error codes and how to diagnose them to preventive measures and when to consider a boiler replacement.

Understanding your boiler and knowing how to handle minor issues can help you maintain an efficient and reliable heating system.

Remember, while it’s important to be familiar with your boiler and its error codes, don’t hesitate to call a professional when necessary. After all, your comfort and safety are paramount.


Where are the error codes on the Worcester boiler?

You can find error codes on a Worcester boiler by pressing the spanner/return button, which will reveal a 3-digit cause code.

Why is my Worcester boiler flashing?

A Worcester boiler flashing indicates low pressure and should be re-pressurised with water to get it working correctly again.

What does the flashing radiator symbol mean on a Worcester boiler?

The flashing radiator symbol on a Worcester boiler indicates that the boiler pump is circulating to disperse leftover heat after the boiler has reached its set temperature.

Why is my Worcester boiler firing but no hot water?

It appears that the issue may be a faulty diverter valve, which is responsible for controlling the flow of hot water to your outlets and heating. Consequently, this could explain why your Worcester boiler is firing but no hot water is being produced.

How do I clear the SE code on my Worcester boiler?

To reset your SE code on your Worcester boiler, press and hold the Spanner button until it becomes orange, press and hold the Eco button until 5A displays, press and release the Eco button, press and release CS, then hold Until brackets appear before releasing, and finally press the spanner button.

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