Common Viessmann Boiler Error Codes

A Viessmann fault code makes it extremely easy to tell what is wrong with your Viessmann boiler, but only if you can understand them properly.

Each error code that appears on the LCD display means something different, and being able to identify them can save you a lot of time.

Here are some of the most common Viessmann boiler fault code details you will see and what they actually signify.

What are Boiler Fault Codes?

A boiler fault code is a shorthand name for a boiler fault. Codes like this (such as Code 5C/5D/5E) provide a quick way to identify problems. A boiler fault code doesn't always mean you'll need to get a new boiler, so don't worry!

For example, if the system identifies a "circuit supply temperature sensor cable broken" issue, it will display it as a code instead.

This makes it much easier to look up specific faults and responses like "control switches to lockout", "control mode communication fault" and "damage to temperature sensor".

Vitotronic 300-K models will have different codes to a Vitodens 100-W burner design: codes are sometimes shared, but most models have their own.

Viessmann boilers use Viessmann boiler fault code information to help you diagnose the problem.

If you find a code that is shorthand for "sensor supply temperature issue", for example, W-model users would be able to find codes specific to that line of Viessmann boilers.

This means that they won't get mixed up with the 100 Vitotronics, 300k with Vitotronic or Vitocontrol-S with Vitotronic lines, as an example.

This can be confusing at first, but it becomes useful as you learn the Viessmann boiler fault code lists for your chosen Viessmann boilers.

A Viessmann boiler like the Vitodens 100 w/ burner, the Vitotronic 100, Vitotronic 300-K with Vitotronic 100, Vitocrossal 300, Vitodens 200, and any other boiler are very easy to confuse, but once you learn the important ones for the boiler you use, you can identify issues with the burner control unit or other parts of the system very quickly.

Fault Codes

Viessmann Fault Code 90, 91, 92, 93, 94, 98, 99, 9A, 9B, 9C, 9E, 9F and AB

All Viessmann boilers: the boiler enters control mode due to a temperature sensor short-circuit.

Fault Code F6, 58, F9, F-E1, F-E2 and F-F6

All Viessmann boilers: the burner fault mode has activated or (another emergency operation has begun) because the fan is not at a standstill (or the plug-in connection is not stable).

Viessmann 5C, 5D, 5E and 5F

Vitotronic 300-K with Vitotronic 200: the boiler has entered a control mode due to a control mode communication fault. Vitotronic 300-k models have four error codes for this fault.

Viessmann Fault Code 10

Vitodens 200-W/222-F, Vitotronic 300/200/200-H/050/200-H/300-K and Vitocontrol-S: the boiler is operating at a Constant Mode outdoor temperature, usually because of a short-circuit in the outdoor temperature sensor.

Vitotronic Vitodens models share this error code.

Viessmann Fault Code 18 and D1

Vitodens 100-W: places the burner in fault mode, often with the DIP switch S2 set to "ON".

Vitotronic 050/200-H: activates automatically at 0°C / 32°F outdoor temperature levels, mainly when it finds the temperature sensor cable broken.

Vitotronic 200-H / Vitotronic 300-K, MW1B with Vitotronic 300 / Vitotronic 300-K, MW2B with Vitotronic 200: the boiler controls as if the outdoor temperature is the standard temperature thanks to a lead break/outdoor temperature sensor fault.

Vitotronic / 100 / 200 / 300 / 050/200-H /300-K / Vitocontrol-S with Vitotronic models, MW1 with Vitotronic 100: the boiler operates on a basis of 0°C / 32°F outdoor temperature, regardless of indoor temperature levels, due to a broken sensor.

Viessmann Boiler Fault Code D4

Vitotronic 300 / Vitotronic 300-K with Vitotronic 300: the boiler is forced to cool down due to a fault with safety equipment or a plug-in adaptor.

Vitodens 200: the boiler either switched to emergency mode or cools down due to an internal BUS fault/open BUS connection.

Viessmann Fault Code A4

Vitodens 222-F: burner blocked - boiler water temperature needs to be reduced, and air will be vented automatically. Can also be a burner control unit fault.

Viessmann Fault Code E1, E7, E8, E9, EA, EB, EC and FF2

Vitotronic 300, Vitodens 200-W / 222-F, Vitotronic 300 models: burner control unit/burner in fault mode due to a low flow rate.

Viessmann Fault Code 20

Vitocontrol-S with Vitotronic 100 / Vitotronic 300 / 300-K / 200 / 100: stand-alone control unit has a short circuit in the common supply temperature sensor.

Vitocrossal 300, Vitodens 200-W/222-F: Regulates without supply temperature sensor (low-loss header), often caused by a short circuit in the system supply temperature sensor. Can sometimes impact the common supply temperature sensor.

Vitotronic 050/200-H< / 200 / 200-H / 300: the sensor of mixing valve components have short-circuited or closed.

Vitotronic 300-K, with Vitotronic 100: controls in a stand-alone manner w/o supply temperature strap-on sensors.

Vitodens 200-W: Regulated without supply temperature sensor. Supply temperature faults can include the system shorting out.

Vitotronic 100, Vitotronic 300-K, with Vitotronic 100: MW1S controls in a stand-alone manner w/o strap-on sensor, usually because the supply temperature may not be high enough.

Vitocrossal 300: Regulates without supply temperature sensor (low-loss header).

Viessmann Fault Code 29, 41, 49, F80, F81, F83, F88 and F89

Vitotronic 200/300: normal operation without influence of return water temperature. Sensor of mixing valve circuit M1 may have been opened.

Viessmann Fault Code A9, BA, BB, BC and FE0

Vitodens 200: boiler cools down due to sensor inputs not reading correctly.

Viessmann Fault Code A0, A1, A2, AA, and AC

Vitodens 200: pump runs at maximum speed due to an open circuit and variable speed heating circuit pump.

Viessmann Fault Code 30

Vitocontrol-S with Vitotronic 100 / Vitodens 100-W (CombiPLUS)/ 200-1: burner blocked due to burner control unit issues/boiler water temperature sensor short-outs.

Other models: the burner control unit is started and stopped through an adjustable high limit thanks to a short circuit in the boiler water temperature sensor.

Viessmann Fault Code B9, ED, F0, F-E5, F-EC, F-ED, F-EE, F-EF, F-FD and F-FF

Vitocontrol-S with Vitotronic 100 / Vitotronic 100 / 300 / Vitotronic 300-K with Vitotronic 300: boiler cools down, fault with the maximum pressure limiter 1 2.

Viessmann Fault Code C2-C8, CD-CF, D2-D8, DA-DF, and E0

All Viessmann boilers: fault state - system cools down due to a fixed high limit or blown fuse F2.

How much does a new boiler cost?

Effectively, new boiler cost can be split into two segments: the first is the actual boiler itself (unit price), and the second is the cost of the boiler being installed (set up) in your property by an expert engineer. 

Here at iHeat, we 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 boiler 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 (guide only).