Viessmann Boiler Fault Codes: Troubleshooting Guide to Fix
Who is Viessmann?
Viessmann is a German manufacturer of heating, cooling, and industrial systems, including boilers. The company was founded in 1917 and is headquartered in Allendorf, Germany. Viessmann is known for its high-quality and efficient heating products, including gas-fired condensing boilers, oil-fired boilers, biomass boilers, heat pumps, and solar thermal systems.
What is a Viessmann Boiler?
Viessmann boilers are widely used in residential, commercial, and industrial applications around the world. They are known for their advanced technology, energy efficiency, and reliability. Viessmann offers a range of boiler models and sizes to suit different heating needs, including combi boilers (combination boilers that provide both heating and hot water), system boilers, and regular boilers.
Viessmann has a strong presence in the UK market and is a popular choice among homeowners, installers, and heating engineers for their quality products and comprehensive after-sales support. The company also emphasises sustainability and has been actively involved in developing eco-friendly heating solutions to reduce carbon emissions.
Viessmann Boiler fault codes and what they mean - In layman’s terms
Understanding the language used in the fault codes
Boiler mode in the below fault codes refers to the specific operational state or behaviour of the boiler when a fault code is encountered. This shows information on how the boiler is behaving under certain conditions related to the fault code. This helps diagnose the issue and understand the symptoms associated with the fault code.
System Behaviour in the below fault codes refers to how the boiler or heating system responds or behaves when a specific fault code is detected For example, in the fault code description for code F6, it states "Burner in fault mode / Emergency operation" under the "System behaviour" column.
This means that when fault code F6 is triggered, the burner of the boiler enters a fault mode or emergency operation, indicating a problem with the burner operation.
Example: Fault code 10 below, the boiler mode suggests ‘Boiler operates based on outdoor temperature of 32°F / 0°C’. This means that when fault 10 is shown, the boiler is expected to operate in a specific mode that is dependent on the outdoor temperature being at or below freezing point.
The information below is listed to help you understand what is happening with your system. The system behaviour and boiler modes are to help you communicate with a qualified gas safe engineer what the issue is you’re experiencing. The will be able to take this information to repair your boiler.
Fault Code 18
Boiler mode for fault code 18
The boiler operates based on the outdoor temperature of 32°F / 0°C or in Constant Mode.
System behavior for fault code 18
This fault code indicates that there is a problem with the outdoor temperature sensor or its associated wiring.
Layman's explanation of fault code 18
The boiler is not able to accurately measure the temperature outside, which can affect its performance. It may be caused by a broken or disconnected outdoor temperature sensor or damaged wiring leading to the sensor. As a result, the boiler might not be adjusting its operation correctly based on the outdoor temperature.
Common fix for fault code 18
Inspect the outdoor temperature sensor and its wiring. Look for any signs of damage or disconnection. If the sensor or wiring is faulty, repair or replace them accordingly. Ensure that the sensor is correctly installed and exposed to the outdoor conditions. If the fault persists, it may require further diagnosis by a professional technician to identify the exact cause of the issue.
Fault Code D1
Boiler mode for fault code D1
The boiler operates based on the outdoor temperature of 32°F / 0°C or in Constant Mode.
System behavior for fault code D1
This fault code points to an issue with the outdoor temperature sensor or its wiring.
Layman's explanation of fault code D1
Similar to fault code 18, fault code D1 indicates a problem with the outdoor temperature sensor or its wiring. It means that the boiler is unable to accurately measure the outdoor temperature, which can impact its performance. This issue could be due to a broken or disconnected outdoor temperature sensor or damaged wiring leading to the sensor. As a result, the boiler may not be able to adjust its operation correctly based on the actual outdoor temperature.
Common fix for fault code D1
Check the outdoor temperature sensor and its wiring. Ensure that the sensor is properly connected and undamaged. If there is a wiring issue or a broken sensor, repair or replace it as necessary. It's also important to verify that the sensor is correctly positioned and exposed to the outdoor environment.
Fault Code 10
Boiler mode for fault code 10
The boiler operates based on the outdoor temperature of 32°F / 0°C.
System behavior for fault code 10
This fault code indicates a short circuit in the outdoor temperature sensor.
Layman's explanation of fault code 10
The boiler is not able to properly measure the outdoor temperature due to a short circuit in the sensor. This can affect the boiler's ability to adjust its operation based on the temperature outside, potentially leading to inefficient or inconsistent heating.
Common fix for fault code 10
Check the wiring and connections of the outdoor temperature sensor. If there is a short circuit, repair or replace the sensor and ensure proper wiring connections. If unsure or unqualified, please call or book a boiler service technician to complete this task for you.
A graphic showcasing the simple descriptions of Viessmann Boiler Fault codes 18, D1, 10, and A4
Fault Codes ‘F6, 58, F9, F-E1, F-E2, F-F6’
Boiler mode for fault code F6, 58, F9, F-E1, F-E2, and F-F6
The burner is in fault mode or emergency operation.
System behavior for fault code F6, 58, F9, F-E1, F-E2, and F-F6
These fault codes suggest a problem with the fan, such as it not operating properly or issues with the plug-in connection.
Layman's explanation of fault code F6, 58, F9, F-E1, F-E2, and F-F6
These fault codes indicate that there is an issue with the fan in the boiler. It could be due to the fan not functioning correctly or problems with the connection to the boiler. As a result, the boiler enters a fault mode or emergency operation to prevent further issues or damage.
Common fix for fault code F6, 58, F9, F-E1, F-E2, and F-F6
Inspect the fan for any obstructions or mechanical issues. Ensure that the fan is operating smoothly. Check the plug-in connection for any loose or damaged wiring. If necessary, clean or replace the fan and repair any faulty connections. If unsure or unqualified, please call or book a boiler service technician to complete this task for you.
Fault Codes ‘5C, 5D, 5E, and 5F’
Boiler mode for fault code 5C, 5D, 5E, and 5F
The control mode of the boiler.
System behavior for fault code 5C, 5D, 5E, and 5F
These fault codes point to a communication fault between the Vitotronic 300-K control system and the Vitotronic 100 of boiler 5-8.
Layman's explanation of fault code 5C, 5D, 5E, and 5F
These fault codes indicate a problem with the communication between different control systems within the boiler. Specifically, there is an issue with the communication between the Vitotronic 300-K control system and the Vitotronic 100 of boiler 5-8. This can lead to disruptions or errors in the boiler's control and operation.
Common fix for fault code 5C, 5D, 5E, and 5F
Verify the communication between the Vitotronic 300-K control system and the Vitotronic 100 of boiler 5-8. Ensure all connections are secure and undamaged. If communication issues persist, it's recommended to contact a Viessmann Trained Installer for further diagnosis and resolution. If unsure or unqualified, please call or book a boiler service technician to complete this task for you.
Fault Code ‘A4’
Boiler mode for fault code A4
The burner is blocked, and the venting program is started automatically.
System behavior for fault code A4
This fault code suggests an air lock in the internal circulation pump or a failure to achieve the minimum flow rate.
Layman's explanation of fault code A4
This fault code indicates that there is a problem with the internal circulation pump, resulting in an air lock or inadequate flow within the boiler. This can lead to blockages and inefficient operation of the burner.
Common fix for fault code A4
Check the internal circulation pump for any airlocks. Bleed the pump or consult a professional to resolve any circulation issues. Additionally, ensure that the minimum flow rate required for proper operation is being achieved. If unsure or unqualified, please call or book a boiler service technician to complete this task for you.
Fault Code ‘OC’
Boiler mode for fault code OC
The burner is blocked.
System behavior for fault code OC
This fault code indicates an insufficient power supply or the presence of a flame signal even after switching off the burner.
Layman's explanation of fault code OC
The boiler has detected a blockage in the burner, which could be caused by insufficient power supply or a malfunction in the flame detection system. This fault code alerts you to a potential issue with the burner and the need for further investigation or repair.
Common fix for fault code OC
Inspect the power supply to the boiler and ensure it meets the required specifications. Check for any loose connections or faulty wiring. If there is a persistent flame signal even after the burner is switched off, it may indicate a malfunctioning flame detection system that requires professional attention. If unsure or unqualified, please call or book a boiler service technician to complete this task for you.
An infographic explaining in simple terms what the Veissmann boiler fault codes F6, 58, F9, FE1, FE2, F-F6, 5C, 5D, 5E, 5F and OC mean
Why you should call a professional to fix your Viessmann Boiler
Safety: Boilers involve complex systems and potentially hazardous components such as gas lines, high-pressure water systems, and electrical connections. Dealing with these components without proper training and expertise can be dangerous and pose a risk of injury or property damage.
Expertise: Professional boiler engineers have extensive knowledge and experience in diagnosing and repairing boiler issues. They are familiar with specific boiler models and their fault codes, allowing them to accurately identify the underlying problem and implement the appropriate solution.
Manufacturer Recommendations: Boiler manufacturers often specify that only authorized or trained professionals should perform repairs and maintenance. Attempting DIY repairs may void the boiler warranty, leaving you responsible for any future repairs or replacements.
Correct Diagnosis: Boiler fault codes can indicate various problems, and it's crucial to diagnose the specific issue accurately. Professional engineers have the necessary tools and diagnostic equipment to identify the root cause of the fault code and address it effectively. DIY attempts may lead to misdiagnosis, resulting in ineffective repairs or further damage to the system.
Proper Repairs: Professionals have access to genuine manufacturer parts and know the correct procedures for repairing or replacing faulty components. They ensure that repairs are performed to industry standards, maintaining the boiler's performance, efficiency, and reliability.
Compliance with Regulations: Boiler installations and repairs are subject to local regulations and safety standards. Professional engineers are familiar with these requirements and can ensure that the repairs adhere to the necessary codes and regulations.
For more detailed and up-to-date information about Viessmann boilers, their product range, and specific models available in the UK, I recommend visiting the official Viessmann website or contacting Viessmann directly.
