Viessmann Boiler Fault Codes

Do you own a Viessmann boiler that has developed a few problems? If there’s an issue with your boiler, then on the screen on the front, it should be displaying an error code which typically Letter+number. Each of these codes is completely unique to the issue the boiler is having.

I know it may seem pretty daunting, as in the back of your mind you might be thinking, boilers cost thousands of pounds! Don’t panic, most error codes on your Viessmann won’t be too serious, they can usually just be solved by a simple reset.

In this blog, we’ll go through whether your Viesmannn boiler is any good if you should think about replacing it, what some of the common fault codes mean and how to fix them, popular models and a full list of errors.

It’s quite a large blog, so if you have a specific question, you should click one of the links below to find your answer quicker:

Are Viessmann boilers any good?

You might be concerned if your Viessmann boiler is showing an error code, naturally, and you might be left questioning whether it’s a worthwhile boiler or you should be looking to replace it.

I can assure you, Viessmann makes fantastic, efficient and reliable boilers. They have fantastic efficiency, are one of the heating giants in Europe despite having a lesser-known name than some of the popular Worcester Bosch or Vaillant, and they also are competitively priced.

There are a few things that set Viessmann boilers out from the rest:

  • They have a stainless steel heat exchanger which is better than most highly-priced boilers in the market
  • Built in shock arrestors which stops any whistling or cracking noises
  • They have a hybrid pressure release valve & condensate pipe, which means you don’t need two holes in your wall, just the one
  • They are built very compactly & won’t take up much room
  • They are surprisingly quiet, which can’t be said for all brands

Despite these fantastic positives, however, just like any boilers, they are still susceptible to the odd error but have faith, it’s probably worth repairing your Viessmann are opposed to getting a new boiler.

What does FF mean on a Viessmann boiler?

“FF” is typically followed by a number on Viessmann boilers and to determine the issue that will require the number. If however, you meant FFF which is a common fault, then it means that there is an internal error with the boiler which is typically the fault of the boiler control unit, this error will often require you to call a boiler engineer.

How do I reset a Viessmann boiler?

You may find when looking into your boiler fault code it asks you to reset the boiler, this is pretty common as a lot of issues are fixed with a simple reset. Unfortunately with Viessmann boilers resets aren’t as straight forward, they aren’t all the same. Sometimes the reset will be a dial or it can potentially be a button, and depending on the boiler you may need to hold the button down or the reset dial in position for several seconds.

If you get stuck & can’t quite figure it out, then you can always call the Viessmann boiler team, who will help explain how to reset it if you are aware of the type of boiler you have.

What does F4 on a Viessmann boiler mean & how do I fix it?

Is an F4 code displaying on your Viessmann boiler? It’s common, in fact, one of the most common, and what it means is that there has been an issue with the flame, or the detection of it.

When you are demanding hot water, there’s no flame being detected which obviously means that the water won’t increase in temperature. Along with this code, it’s also very common for your boiler to actually lockout, to ensure there isn’t any danger, and the components aren’t damaged further, it’s a safety mechanism.

This error can be a wide variety of different things including the electronics, flame sensor, gas valve, burner, PCB, spark generator or ignition lead. Unfortunately, this error isn’t one in which you can fix on a DIY basis, and you will need to call a boiler engineer.

What is an F2 code on a Viessmann boiler?

One of the other most common errors on Viessmann boilers, the Vitodens in particular, is the F2 fault code. This fault is an indication that the burner has been locked out, although it doesn’t always mean there is an issue with the actual burner itself.

This is often caused by the pump, which is what is responsible for circulating the hot water due to the risk of it overheating, it will lock the boiler out.

Yet again, like the other common codes, this isn’t one you should try and tackle yourself. It’s an issue with the pump, which is within the boiler casing, which is not something you should remove yourself without a qualified engineer. Unfortunately, the way of solving this issue is to call a boiler engineer.

Popular Viessmann boiler models

Viessmann offer a wide range of boilers for all shapes and sizes of homes, and I’ll cover the fault codes for the wide majority of them in the list next, but here is a list of some of the most common Viessmann boilers in the range:

  • Viessmann Vitodens 100W – 26 to 35kW
  • Viessmann Vitodens 050W – 29 to 35kW
  • Viessmann Vitodens 200W – 26 to 35kW
  • Viessmann Vitodens 111W DHW – 26 to 35kW
  • Viessmann Vitodens 222F – 19 to 35kW
  • Viessmann Vitodens 242F – 18 to 26kW

Typically these boilers will be available in System & Combi ranges.

List of Viessmann boiler fault & error codes

Now the list you’ve been waiting for. I’ve scoured the internet, read countless Viessmann boiler manuals and pulled together a comprehensive list of Viessmann boiler fault codes for you, including a description of the fault & potential solution, you can also use the search bar to find your fault code easier:

Error CodeDescription of FaultPossible Solution
2The safety has been activated and you've been locked out.This is typically due to another fault, but try reset the boiler
10The sensor for the outdoor temperature has short circuited.To get this issue fixed, you will need to call a boiler engineer.
19There's a fault with the communication of the outdoor temperature sensorTo get this issue fixed, you will need to call a boiler engineer.
20This is an issue with the temperature sensor, but it can be in relation to it short circuiting, or the system flow or supply temperature.To get this issue fixed, you will need to call a boiler engineer.
21The sensor for the return water temperature has short circuited.To get this issue fixed, you will need to call a boiler engineer.
25The temperature of the boiler whilst in operation has been consistently high.Reset the boiler.
26When the boiler is operation there has been a continuous relay test.Reset the boiler.
28There is an issue with the supply temperature sensorTo get this issue fixed, you will need to call a boiler engineer.
30The sensor for the water temperature has short circuitedTo get this issue fixed, you will need to call a boiler engineer.
35The boiler is not activatingYou can fix this by turning the emissions switch back to its original setting & resetting the boiler
38There is an issue with the sensor for the water temperatureTry reset the boiler, if the issue persists you will need to call a boiler engineer.
52This error can be one of two things, the temperature supply sensor may have short circuited causing a low loss header, or the flow sensor has shorted outTo get both these issues fixed, you will need to call a boiler engineer.
07 & 09The air pressure isn't correct when it is in standby mode & the boiler has locked out.Try re-pressurise the boiler and reset it.
04, 05, 06 & 08The speed of the fan is either too low or high when the boiler startsTry reset the boiler, if the issue persists you will need to call a boiler engineer.
0AThe speed of the fan is faultyTo get this issue fixed, you will need to call a boiler engineer.
0BThe burner is blockedThis could be a multitude of different things so I would advise calling a boiler engineer.
0CThere is an insufficient power supply or the flame signal was still present after switching the burner onTry reset the boiler, if the issue persists you will need to call a boiler engineer.
0DThe controls have been locked out.This can be because you've reset the boiler too many times, so give it a few minutes.
0FA service or maintenance is requiredYou will need to call a boiler engineer.
10, 14 & F3, F4The flame signal is not presentCheck the gas supply, try reset the boiler & if the issue persists you will need to call a boiler engineer.
18 & D1The outdoor temperature sensor cable is brokenTo get this issue fixed, you will need to call a boiler engineer.
1A & 1BThe flow sensor is faultyTo get this issue fixed, you will need to call a boiler engineer.
1FThe rate of the flow is exceeding the recommendedTo get this issue fixed, you will need to call a boiler engineer.
F80, F81, F83, F88, F89 & 29, 41, 49The sensor for the return water temperature has an open circuitTo get this issue fixed, you will need to call a boiler engineer.
40 & 44The temperature sensor has short circuited on circuit 2To get this issue fixed, you will need to call a boiler engineer.
48 & 4COn the supply temperature sensor there is a cable that is broken.To get this issue fixed, you will need to call a boiler engineer.
50-51 & 58-59There is an issue with the temperature sensor for the DHW tank, it's either short circuited or has an open circuit.To get this issue fixed, you will need to call a boiler engineer.
55-57A service or maintenance is required.You will need to call a boiler engineer.
5A & B7, B8There's a low loss header or lead break with the supply temperature sensor.You will need to call a boiler engineer.
5C, 5D, 5E & 5FThere is a fault with the communication internally within the boilerYou will need to call a boiler engineer.
BD, BE, BF & 60, 68, 70, 78The sensor for the temperature has an open circuited or has short circuited.You will need to call a boiler engineer.
80-83 & FDThe burner control unit or the sensor for the water temperature has short circuited.You will need to call a boiler engineer.
88-89 & E6This is a fault with the burner control unit.You will need to call a boiler engineer.
8C, 8D, 8E & 8FThere is a fault with the communication internally within the boilerYou will need to call a boiler engineer.
90-94, 98-99 & 9A, 9B, 9C, 9E, 9F & ABThere has been a short circuit in the sensor for the temperatureYou will need to call a boiler engineer.
A0-A2 & AA, ACSafety equipment fault or a BUS faultYou will need to call a boiler engineer.
A2KM-BUS faultYou will need to call a boiler engineer.
A3, B0, F1 & FE1-FE2 The gas burner is blocked, often because of the incorrect positioning of the flue.You might be able to move the flue slightly, but if not you will need to call a boiler engineer.
A4In the variable speed heating circuit pump there is an open circuit with the BUS connection.You will need to call a boiler engineer.
A5There isn't too much information about this one, apart from the fact it's an open or shorted circuit.You will need to call a boiler engineer.
A7The programming unit is faulty - you typically only see this right after installation.Get in touch with whoever installed the boiler.
A8There is either air lock in the circulation pump, or the minimum flow rate hasn't been achieved.Try reset the boiler, if the issue persists you will need to call a boiler engineer.
A9, BA, BB, BC & FE0There is a fault with the communication internally within the boilerYou will need to call a boiler engineer.
ADThe isolation valve has an error with it's configuration.If you've recently had work done on your boiler, get back in touch with them.
B1The programming unit has a communication error.Try reset the boiler, if the issue persists you will need to call a boiler engineer.
B2The boiler isn't reading the sensor inputs correctly.You will need to call a boiler engineer.
B3 & E5There is an internal fault and the boiler hasn't stored the data pointsYou usually only see this during a service.
B4 & B5There's a fault with the electronics internally within the boilerYou will need to call a boiler engineer.
B6The hardware is invalidIs it a recent installation? Contact the boiler engineer that installed the boiler.
B9 & FEE, FEC, FEF, FFD, FFF, F0, FE5 & EDThere's a fault internally.You will need to call a boiler engineer.
C1Safety equipment externallyNo action
CD-CF, C2-C38 & DA-DF, DF, D2-D8 & E0The solar control unit & KM-BUS have an open circuit or there is a communication fault.You will need to call a boiler engineer.
CA, CB & C9There has been an issue due to the maximum pressure.Release some of the pressure in the boiler & reset it.
CC & F0There is an open circuit or a differential in the air pressure sensor.You will need to call a boiler engineer.
D4The fixed high limit has responded of F2 has blown.You will need to call a boiler engineer.
D5The cascade control unit is not being logged into when the boiler is started.You will need to call a boiler engineer.
E1, E7-E9, EA, EB, EC & FF2The ionisation is too high during the calibration.Try reset the boiler, if the issue persists you will need to call a boiler engineer.
E2-E3During the calibration the water flow rate has been too low.Try reset the boiler, if the issue persists you will need to call a boiler engineer.
E4There's a fault with the supply voltage.You will need to call a boiler engineer.
EE & EFThe flame signal is missing or too weak.Try reset the boiler, if the issue persists you will need to call a boiler engineer.
F5The switch for the air pressure is faulty.You will need to call a boiler engineer.
F6, F9 & FE1-FE2, FF6 & 58This is an issue with the gas pressure switch, it's showing there's no gas pressure.Is your gas supply working? Test other appliances to make sure. If not you will need to call a boiler engineer.
FA & FBThe burner is in fault mode.You will need to call a boiler engineer.
FB7 & FF2, FF4, FF7-FF9Faulty or not inserted coding cardThis is in relation to the coding card and burner control unit, contact whoever has worked on your boiler recently.
FCFaulty gas valve.You will need to call a boiler engineer.
FEThere is a fault with the main printed circuit board (PCB).This can be quite an expensive one & may even mean replacement. You will need to call a boiler engineer.
FE4The voltage has been too low multiple times.You will need to call a boiler engineer.
FFA, FFB & FRThere is a fault with the fan.You will need to call a boiler engineer.

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Mat

A complete novice trying to navigate in the world of DIY. I bought my first home about 2 years ago & ever since I've been trying to research & learn how best to tackle common household problems.

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