And How To Fix Them
Modern domestic boilers are incredibly efficient, reliable, and safe. This means they have sensors built in to ensure that they are running smoothly. If these sensors detect any kind of issue, the boiler will safely shutdown to avoid any kind of more serious malfunction. When this happens, they will display an error code on the digital read out on their front panel – these codes help you to diagnose what’s gone wrong quickly and easily.
In this article, you’ll find information on the most common error codes from three leading brands: Vaillant, Worcester Bosch, and Ideal. Use the links below to quickly skip to the relevant section and find out what each error code means
As you will see, many of these errors can have multiple causes, and can be difficult to repair. While this is primarily aimed at plumbers and heating professionals, if you are thinking of fixing your own boiler, it’s always best to contact a reputable, Gas Safe registered heating engineer to carry out any work on your boiler.
The table below shows most common error codes on Vaillant boilers, so you can quickly find what you need to fix your customer’s heating. Once you’ve worked out what the fault is, be sure to shop our extensive range of Vaillant Boiler Parts to find official replacements and spares.
These error codes apply for ecoTEC, ecoTEC Plus and ecoTEC pro models. For model-specific advice, be sure to consult the operating manual for that Vaillant boiler.
Fault Name & Description
The water pressure in the boiler is too low. To fix, you need to increase the water pressure by allowing more water into the boiler via the filling loop.
If this error is recurring, it suggests there is a leak somewhere in the heating system.
The temperature differential between water leaving and entering the system has reached its maximum (35°C).
Water circulation fault. The system has detected a temperature rise that is greater than 10°C per second.
Incorrect flame detection. The boiler is detecting that something is not right with its ignition, so as a safety precaution it turns off.
Ignition failure. This means that the boiler could not ignite correctly.
Start-up failure. This means that the boiler flame failed to ignite on start-up. This can be caused by a number of different issues:
Fan fault. The boiler has detected an issue with airflow, typically caused by the fan not working properly.
Gas supply fault. This means that the boiler has detected an insufficient supply of gas for the boiler to function. This error will often be accompanied by f28 and f29 errors, as these deal with ignition failure.
Faulty Gas Valve. This means that the boiler has detected gas flowing through the gas valve at times when it should have been closed. Upon detecting this, the boiler shuts down safely until the issue can be fixed.
No pressure change detected when pump started. This means that the boiler has detected no change in water pressure, but the pump is supposed to be running.
In the table below, you’ll find information about the most common error codes on Worcester Bosch boilers, including how to fix them and which parts could be responsible for the fault. Once you’ve tracked down what’s causing the error, be sure to check our huge range of official Worcester Bosch boiler parts to get what you need.
These error codes apply across Worcester Bosch’s CDI and Greenstar models. For specific information about the boiler you are working on, be sure to check that model’s manual.
Fault Name & Description
Safety Temperature Limiter has tripped. The boiler has detected an issue with its temperature and has safely shut down. The part of the boiler causing the issue will depend on the error code that follows the E9 code:
Flame not detected. This means that the boiler cannot detect a flame after ignition, so it has shut down safely until the problem is rectified. This can be caused by a number of issues:
“False Flame” - flame detected when boiler was shut off. This fault means that the boiler has detected a flame when there should not be one because the boiler is either off or on standby. Upon detecting the flame, the boiler will shut down for safety. This can occur for a number of different reasons:
The table below contains a list of the common error codes that can occur with Ideal Boilers, including the name of the error and which part of the boiler or heating system might be responsible. If the issue is with the boiler itself, we have a huge range of official Ideal Boiler parts, so you can find exactly what you need to get your customer’s heating up and running in no time.
These apply to Ideal’s Logic range of boilers. For model specific advice, be sure to check the relevant manual.
Fault Name & Description
0 or 00
Standby. Not really a fault, this just means that the boiler is idle. If you run a tap or turn on the heating, then the boiler should “wake up”. If the heating should be on, but it is still showing the standby code, check that the heating controls are working properly.
C or D
Central Heating Demands (C) or Hot Water Demands (D). Again, this is not really a fault – it just means that the boiler is responding to demand for either heating or hot water. To clear the screen, you can press reset on the front panel of the boiler.
Low Water Pressure. This means the water pressure in the heating system is too low. To fix, you need to let more water into the system via the filling loop.
If this error keeps recurring, it suggests that there may be a leak somewhere in the heating system that is causing the pressure to drop.
DHW Thermistor Fault. This means the thermistor that the boiler uses for temperature measurement is not giving correct readings. This can simply mean the boiler needs to be reset. If after reset the error continues, typically you will need to replace the thermistor or sometimes the boiler’s PCB.
Lack of Water Flow. The boiler has detected that the temperature of the flow pipe is too high, caused by overheating or a lack of water flow around the system, causing the hot water to back-up in the flow. First, try resetting the boiler. If the error persists, there could be a few different causes:
Flame Loss During Operation/Ignition Lockout. This means the boiler has detected an issue during ignition, or the flame has gone out when it should not have. The boiler will lockout as a precaution.
At Wolseley, we are the trade specialists for both boilers and parts. So, whatever fault you are trying to fix, you can rely on us to have what you nee to get the job done. Register a trade account with us today and get free access to industry leading parts identification tool PartsArena, with exploded diagrams and thousands of images to help you find exactly the right parts.