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Last updated: 7th May, 2024


What is a Boiler PCB?

What is a Boiler PCB?

Key takeaways

  • A boiler PCB is the central control unit responsible for efficient and safe functioning.
  • Understanding and identifying PCB faults can prevent costly repairs or replacements.
  • Professional intervention may be necessary for complex issues or safety concerns.

Our helpful PCB blog provides a comprehensive explanation of the Printed Circuit Board (PCB) in boilers, detailing its function as the control centre for boiler components and offering insights into its importance for efficient boiler operation.

A boiler PCB, or Printed Circuit Board, can be thought of as the brain of your central heating and hot water system. 

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This vital component is responsible for maintaining the correct temperature, pressure, and current flow, ensuring that all electronic components in the boiler work together efficiently and safely. 

The PCB plays a critical role in synchronising the various elements of your boiler, helping it to function continuously without interruption.

Understanding the intricacies of a boiler PCB is essential for identifying potential faults and addressing them accordingly. 

A malfunctioning PCB can lead to issues with the temperature, pressure, and overall performance of your boiler and central heating system. If left unchecked, a faulty PCB could result in costly repairs or even the need for a complete boiler replacement.

In some cases, it may be necessary to seek professional intervention to ensure the safety and functionality of your boiler, particularly when dealing with complex components like the PCB. 

Knowing when to call in a professional, and being well-informed about the various factors that could influence the decision to replace a boiler or PCB, can help you keep your home warm and comfortable with minimal disruption.

Understanding the Boiler PCB

A boiler Printed Circuit Board (PCB) is an essential component in a modern boiler system. Often referred to as the brain or nerve centre of a boiler, the PCB plays a critical role in ensuring that the boiler functions optimally. It consists of an electrical board with interconnected components that form an electric circuit, responsible for controlling, protecting, and monitoring various aspects of a boiler's functioning.

The purpose of a boiler PCB is to sync all boiler components in the system. This synchronisation allows for seamless communication between various parts of the boiler, ensuring the created hot water and central heating run efficiently. Without a functioning PCB, the entire boiler may fail, leading to costly repairs and inconvenience.

In a boiler system, electrical components such as sensors, timers, and thermostats rely on the PCB to function. The PCB processes information from these components while sending signals to control different parts of the system, ensuring proper activation or deactivation of components as required.

Given the significance of PCBs in a boiler system, it's essential to identify possible issues at an early stage and rectify them. Common PCB faults include erratic behaviour of thermostats, boiler failing to switch on or off, or continuously running without heating. These faults may indicate the need for a PCB repair or replacement.

Boiler PCB faults can stem from various factors, like power surges, electrical component wear and tear, or corrosion caused by moisture exposure. Preventative maintenance and regular servicing can help keep the boiler and its PCB in optimal condition, extending their lifespan and ensuring a safe, functional heating system.

In conclusion, the boiler PCB is a vital component that manages and synchronises the workings of an entire boiler system. Ensuring the boiler PCB remains in good condition is necessary for maintaining a reliable and efficient hot water and central heating system.

Identifying PCB Faults

The primary role of a PCB in a boiler is to act as the control hub for all its components, ensuring smooth communication and synchronicity. Any issue with the PCB can disrupt this communication, resulting in irregular boiler operation.

One common sign of a faulty PCB is an intermittent display panel operation. In this case, the display panel may work erratically, making it difficult to monitor the boiler's performance accurately. Generally, flashing lights on the display panel could also indicate a PCB fault. Depending on the boiler's make and model, these lights may be green, red or blue. It is essential to be cautious and avoid making assumptions until a professional can confirm the issue.

In some cases, a boiler may experience a total power outage due to a PCB issue, resulting in no display or boiler operation. This is an obvious indication of a fault and requires urgent attention from a Gas Safe engineer. The absence of power signifies that the boiler's PCB is unable to function correctly, thus affecting the entire system.

Another potential sign of a PCB fault is sporadic boiler operation. The PCB may not send appropriate signals or commands to other components, hindering the boiler's overall functionality. Errors may also be detected by the PCB, which will emit a specific error code and halt further operation until the issue is addressed. These error codes can be useful in diagnosing the problem and seeking professional help for repairs.

In conclusion, identifying PCB faults in boilers is of utmost importance for maintaining their efficiency and safety. Carefully observing the display panel, monitoring the boiler's functionality and performance, and understanding the potential error codes can aid in timely detection and resolution of any issues that may arise due to a faulty PCB.

Indications of Malfunctioning PCB

A malfunctioning Printed Circuit Board (PCB) in your boiler can cause a range of issues. Being aware of the signs and symptoms can help you take preventative measures and avoid costly repairs. Here we discuss the common indications that signal a possible PCB fault.

A burning smell emanating from the boiler can be a clear sign that the board's components are overheating or burning. This issue should not be taken lightly, as it could potentially lead to a more serious problem or even a fire hazard.

Error codes displayed on the boiler panel may directly indicate an issue with the PCB. Different boilers have various codes, but it's crucial to consult your boiler's manufacturer guidelines and recognise any fault codes related to the PCB.

Loose connections on the circuit board can result in erratic behaviour of your boiler. Wires may become loose over time due to vibrations or poor installation. Periodic inspection of the connections can help prevent the loose wires from causing any damage to your PCB.

A water leak in the boiler can be detrimental to the PCB, as moisture can seep into the board and cause short circuits. Identifying and rectifying the source of the leak is vital to avoid further damage and maintain boiler functionality.

Unusual noise from the boiler can indicate a malfunctioning PCB. If you hear any odd sounds like clicking, buzzing, or humming, it may be related to electrical components on the PCB and should be inspected by a professional.

Lastly, persistent or multiple fault codes displayed on the boiler panel is another indicator of a possible PCB issue. Although some fault codes may signal other potential problems within the boiler, continuous fault codes pointing to the PCB could mean that it requires immediate 

Understanding Boiler Components

A boiler is a complex system consisting of various components working together to produce hot water and central heating. Let's delve into the primary components:

The Printed Circuit Board (PCB) serves as the motherboard, controlling and synchronising all electronic components within the boiler. It ensures the system functions effectively and safely. In case of malfunction, the PCB triggers a boiler lockout, preventing further damage or potential harm.

The fan is designed to expel combustion gases generated within the boiler through the flue. This component is crucial for maintaining a safe environment within the home.

The pump circulates heated water from the boiler to radiators, providing central heating. It plays an essential role in maintaining a comfortable temperature within the property.

The heat exchanger transfers heat from the burning fuel to the water in the system. This component is responsible for heating the water that is later pumped through the radiators.

The gas valve controls the supply of gas to the boiler's burner. It operates in conjunction with the PCB, ensuring that gas flows into the burner only when deemed safe.

The pilot light refers to the small flame that remains lit to ignite the main burner when heat is required. In modern boilers, this has been replaced by electronic ignition systems.

The thermistor is a temperature-responsive sensor that sends data to the PCB. It helps regulate the heat output by optimising boiler functioning, ensuring efficient energy use.

An NTC thermistor operates similarly, but it differs in design. The NTC thermistor's resistance decreases with increasing temperature, allowing the PCB to make calculated decisions based on this information.

These various electronic components, such as the fan, pump, heat exchanger, gas valve, pilot light, thermistor, and NTC thermistor, all communicate through the PCB. Accurate communication is essential to maintain optimal efficiency, safety and performance of the boiler. It is vital to have a comprehensive understanding of these components to address potential faults and ensure seamless functioning of your boiler system.

A boiler's Printed Circuit Board (PCB) acts as the central control centre for your hot water and central heating system. It connects and controls various parts of the system, including the central heating pump, valves, and other sensors. The PCB manages the transfer of heat to the central heating system and ensures that hot water is supplied to the property.

In a typical setup, the boiler heats water and sends it through pipes to radiators or underfloor heating systems, enabling homes to maintain a comfortable temperature. The hot water flows under high pressure, ensuring an efficient and effective distribution of heat. The PCB plays a crucial role in controlling the temperature of the water and maintaining the entire system's balance.

Such a sophisticated system is not without its challenges. Issues can arise with PCBs such as no power, lockouts, or inability to maintain the correct pressure. These problems can cause discomfort for homeowners and even leaks in the heating system.

When the PCB is functioning properly, indicator lights provide useful information on the operational status of the boiler and central heating system. These lights help identify common issues, such as overheating, low pressure, and electrical faults. They also enable technicians and homeowners to evaluate and respond to problems quickly, preventing further complications and potential system damage.

Regular maintenance of your heating system is essential for spotting any potential issues with your boiler PCB. A skilled technician can assess the functionality of the PCB as part of a thorough inspection, ensuring that your central heating system remains in optimal working order.

Professional Intervention and Safety

When dealing with a boiler PCB, it is paramount to prioritise safety and seek professional assistance. A faulty PCB can pose various hazards, from electrical dangers to potential gas leaks. It's crucial to have a qualified gas safety engineer diagnose and address such issues, as they are well-equipped to handle these delicate situations.

A gas safety engineer, commonly referred to as a gas safe engineer, holds the necessary qualifications and certifications to perform maintenance, repairs, and installations involving gas appliances. These professionals possess the technical expertise to assess the workings of a boiler PCB, ensuring clear communication with other boiler components. Additionally, they can provide valuable insight into possible faults, preventing further damage to the system.

Apart from assessing communication, a gas safety engineer can efficiently diagnose faults within the PCB. They have the knowledge to identify any electrical glitches or disruptions in the boiler's gas valve sequence, preventing severe consequences associated with these issues. Additionally, they have access to crucial information, including manufacturer specifications and guidelines, which aids in providing accurate and reliable repairs.

Factors Influencing a New Boiler or PCB Replacement

When considering a new boiler or PCB replacement, there are various factors to take into account. One of the primary elements is the cost, as buying a new boiler or repairing a faulty PCB can be a significant expense. The brand and model of your boiler can impact the price, as different models may require specific types of PCB boards or entail varying repair costs.

Another factor to consider is the extent of the damage to the PCB, as this could affect the repair or replacement cost. If the problem is a minor wiring issue or a malfunctioning air pressure switch, it may be more cost-effective to address the issue directly rather than replacing the entire PCB. Yet, if the boiler experiences a lockout or if crucial parts of the circuit board have burnt out, it may be necessary to install a new PCB.

The cost of labour in your area can also influence your decision. In some regions, professional services might be more expensive than in others. As a result, it's wise to obtain multiple quotes from reputable heating engineers to ensure you receive competitive pricing for the repair or replacement.

In addition, it's essential to consider whether the boiler is still under warranty. If the warranty covers the necessary repairs or replacement, it could greatly reduce the out-of-pocket cost. However, carefully review the terms of your warranty to determine whether it covers PCB issues or if certain repair work may void it.

Lastly, evaluate the boiler's overall maintenance history. A well-maintained boiler is less likely to require frequent repairs, increasing the likelihood of a cost-effective PCB repair. Conversely, an older or poorly maintained boiler may experience continuous issues, rendering a new boiler a more economical long-term solution.

Boiler Brands and Their Compatibility with PCBs

When discussing boiler PCBs, it's essential to consider the compatibility of various boiler brands and their respective appliances. A well-known and respected boiler manufacturer is Worcester Bosch. Their boilers are considered a smart investment due to their high quality and reliable performance.

Compatibility with boiler PCBs differs among boiler manufacturers. Some brands design their appliances for ease of integration, while others may require specific make and model pairings for full functionality. It's crucial to research and compare the best boiler brands when looking to upgrade or maintain your current system.

Labour costs are a variable component when determining boiler and PCB compatibility. While some brands offer user-friendly installation and replacement processes, others may incur higher labour fees. Consequently, it's worthwhile to investigate the technical aspects of a boiler's PCB integration when making a purchase decision.

Another point to consider is the availability of refurbished or reconditioned parts. Some boiler manufacturers supply reconditioned PCBs, which can significantly reduce costs and prove more economical in the long run. Nevertheless, it's essential to consider the potential risks associated with purchasing refurbished components and weigh the benefits against the initial investment.

In conclusion, careful analysis of the compatibility between boiler brands and their respective PCBs ensures optimal performance while minimising costs and future complications. By thoroughly researching boiler manufacturers and PCB integration requirements, homeowners can make well-informed decisions that ultimately provide efficient and reliable heating solutions.

When to Get a New Boiler

Boilers play a significant role in the functioning of a home, providing heating and hot water. A boiler's PCB (Printed Circuit Board) acts as the brain or nerve centre, controlling each component and ensuring proper communication between parts. If you encounter problems with the boiler's PCB, it could lead to a costly repair or even replacement. Understanding when to get a new boiler is essential to avoid unexpected expenses and inconvenience.

The first sign to consider a new boiler is an increase in energy bills. As boilers age, their efficiency tends to decrease, causing more energy consumption. If you notice that your energy bills have spiked, it might be a good time to invest in a new boiler. More advanced models offer improved efficiency and lower running costs, which can save you money in the long term.

Regular breakdowns or repairs are another indicator that a new boiler might be necessary. If you find that your boiler requires repeated fixes, especially in relation to the PCB, replacing the entire unit could be a more economical and time-saving solution. It's also worth noting that spare parts for older boilers can be more challenging to find, and the costs of frequent repairs can pile up, making a replacement a wiser choice.

The age of your boiler is another crucial factor in determining whether it's time for a new one. Most boilers have a lifespan of around 10 to 15 years, but factors such as maintenance and usage can impact this. If your boiler has reached or surpassed this age range, it's advisable to start considering a new unit. The latest boiler models come with better technology, offering a more energy-efficient and environmentally friendly solution.

Safety concerns should also not be overlooked. When a boiler becomes faulty due to issues with the PCB or other components, it can pose safety risks such as gas leaks or carbon monoxide poisoning. In such cases, getting professional advice and considering a new boiler is of utmost importance.


Here at iHeat, we want to remove all of this undue stress and make the decision making process of upgrading to a new central heating system, as easy as possible.

Boiler costs can vary depending on a number of factors including their brand, model, fuel, output, warranty, labour and installation type. Typically a new boiler will cost between £1,845 and £3,500, below is a list of average boiler installations offered by iHeat.

Installation Type

Price (inc VAT)

Combi to combi swap


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System to combi conversion


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New boiler install


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Back boiler to a combi


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System to system


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A boiler PCB, or Printed Circuit Board, is a vital component within a boiler, acting as its control centre and overseeing the actions of various electronic elements. The PCB facilitates communication between these parts, ensuring seamless operation of the central heating system and maintaining optimal temperature levels.

Boiler vibrations can sometimes cause damage to the PCB, specifically cracks or fractures in the solder joints. These weak points in the circuit board can then result in sporadic operation of the boiler or even electrical faults. Another common issue with PCBs is miscommunication between the programmer and other components in the boiler. This may be caused by damaged solder joints, water damage, or weak electrical connections.

When it comes to fixing boiler PCB issues, a professional engineer should be consulted to diagnose and address the problem. They can identify any fractures or cracks and repair the solder joints accordingly. However, if the PCB is beyond repair, it may be necessary to replace it with a new one.

Preventative measures can help to avoid boiler PCB damage. Regular maintenance checks can detect any potential issues before they develop into more significant problems. This includes ensuring that the boiler is secure in its location to minimise vibrations, inspecting electrical connections, and checking for water damage.

In conclusion, boiler PCBs play a crucial role in the functionality of a central heating system. Familiarising yourself with the basics of PCBs and common issues will ensure that you are prepared to take swift action if needed, maintaining an efficient and functioning system.

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Frequently Asked Questions

What is PCB on a boiler?

PCB stands for Printed Circuit Board on a boiler. It functions as the motherboard or control centre of your boiler, connecting all the components, sensors, and controls to ensure smooth and efficient operation. The PCB plays a vital role in regulating your hot water and central heating system.

How much does it cost to replace a PCB?

The cost to replace a PCB in a boiler varies depending on the make and model of the boiler. Typically, the cost ranges from £250 to £450. This includes both the cost of the new PCB itself and the labour charges for a professional engineer to complete the work.

Is it worth replacing the PCB on a boiler?

It depends on the age and overall condition of your boiler. If your boiler is relatively new and in good shape, replacing the PCB might be a cost-effective solution for fixing issues related to the circuit board. However, if your boiler is older and has other faults or issues, it could be more economical to invest in a new boiler altogether.

What is PCB in a Vaillant boiler?

Vaillant is a popular boiler brand, and like other boilers, its systems also use a PCB. In a Vaillant boiler, the PCB acts as the heart and mind of the boiler, managing communication between various components and ensuring the smooth function of the heating and hot water system.

How do I know if my PCB is damaged?

Some signs that your boiler's PCB may be damaged include inconsistent display panel operation, flickering lights, unresponsiveness, and irregular boiler function. Additionally, if you notice problems with your central heating or hot water supply, it could also indicate a faulty PCB.

How do I know if my PCB is not working?

Similar to identifying damage, if your PCB is not working correctly, you may experience issues such as an unresponsive boiler, inconsistent heating and hot water supply, or malfunctioning display panels. If your boiler displays any of these symptoms, it is essential to seek professional advice from a qualified engineer who can diagnose and fix the problem.

How do you fix a PCB problem?

Fixing a PCB problem on a boiler should always be left to a qualified and experienced engineer. They will inspect the boiler, diagnose the issue, and recommend the most suitable course of action, which may involve repairing or replacing the PCB. It is crucial not to attempt to fix a boiler PCB problem yourself, as it can lead to severe damage to your heating system and pose safety risks.

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Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.