Viessmann Boiler Problems, Common Causes & How To Fix

Common Viessmann boiler problems & how to fix them

Viessmann is well known for the high quality of its heating systems. They even claim on their website that they produce the ‘UK’s most reliable boilers’ so hopefully your Viessmann boiler problems can easily be fixed and rectified

If your looking for Viessmann fault codes, skip right to the part of the blog near the bottom for the full list. If you want to know more or if your issue is fixable or common, then read on.

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Who are Viessmann

Viessmann recently celebrated one hundred years in business, and they have sales offices in eleven different countries. This German boiler company has rapidly become one of the best boiler brands in the UK and renowned for reliability.

So, while Viessmann boiler problems may not happen often, there will be times when a fault develops that needs attention after the boiler installation

In this article, we’ll take about which problems are most common. Then we’ll look at which issues you can fix yourself and which need a visit from a Gas Safe engineer.

Whether you have Viessmann Vitodens 200 problems or need help with Viessmann Vitodens 100 troubleshooting, we can help!

What Are The Most Common Viessmann Boiler Problems?

Many of the common problems are quick and easy to identify. Radiators not warming up and having to take a cold shower are likely to be spotted pretty quickly!

Some problems, though, start small and get bigger over time, especially with cheap boilers. That tiny leak from the radiator will become a bigger issue if not quickly fixed. Fixing it is much better than paying what a new boiler cost.

Some of the most common boiler problems include:

• No hot water but the heating works.
• Boiler not firing up.
• Low boiler pressure.
• Faulty fan
• Faulty PCB
• Faulty flow switch
• Burner blockage
• Radiators not getting hot.

New Viessmann boiler not starting up

From time to time a new Viessmann boiler may not start up, if this is the case you are covered under the warranty, however, you may want to know why to ensure that you are covered. Here are some of the reasons why a new Viessman boiler may not work:

Faulty fan

If the fan is faulty in a Viessmann boiler then it will not work as it is unsafe due to the fact that the fan will not be able to ensure that harmful gasses are removed from your home properly. This safety feature will is known as a lockout and your Viessmann boiler won’t start until the faulty fan is fixed.

As this is a mechanical problem with the boiler it is the fault of the manufacturer to fix and if your boiler is under 10 years old will be covered by the warranty.

Fault PCB

The printed circuit board or PCB is the boilers brain and tells it what to do and when, therefore if you have a new Viessmann boiler with a faulty PCB will often not work at all. There is not a lot that can be done here other than replace the PCB or the whole boiler itself, as a faulty Viessmann PCB could be costly to replace.

A faulty PCB in a Viessmann boiler is a defect that is covered under the boiler warranty, therefore if this is the case you should contact Viessmann to either replace the PCB or the boiler. This should be of zero cost to you too.

Faulty Flow Switch

A faulty flow switch is a serious problem as the flow switch ensures that gas is flowing correctly through the pipes in and around your boiler. This means that if the Viessmann flow switch is faulty, then gas could be flowing incorrectly which could be dangerous, which in turn will cause the boiler to lock out as a safety precaution. Your boiler will not turn back on until this is fixed.

How To Fix A Leaking Viessmann Boiler

A leaking boiler is usually a sign of a serious problem. It can lead to other components rusting or the shorting of electrical components in the boiler. This is something that needs immediate attention.

Boiler Pressure Valve Fault

When the pressure valve is the source of the leak, first check if the boiler pressure is too high.

If the gauge on the boiler is in the red, then you can bleed the boiler to reduce it.

Sometimes this can be caused by sludge or an obstruction in the system. In that instance, you’ll need to call out a Gas Safe engineer.

Leaking Pipe Fittings

If the boiler leak is coming from pipe fittings, a ¼ turn of the fitment might do the trick. If that doesn’t work, then an engineer will need to check the PTFE tape inside of the Fitting.

Seals in The Boiler Pump

Over time, the rubber seals can become damaged, which is a common cause of leaks in older types of boilers. Often the level of corrosion means that it makes more sense to get a replacement boiler than attempt repairs.

Fixing Viessmann Boiler Problems Yourself

If you’re having problems with your Viessmann boiler, troubleshooting may mean that you can sort out simple issues yourself & stop you needing to pay the boiler replacement cost.

Our fault-finding tips help you to fix three common problems.

Frozen Condensate Pipe

The condensate pipe drains the small amount of wastewater produced by condensing boilers. In cold spells, the water freezes and blocks the pipe.

To sort out this one just pour hot water over the blocked area until the ice has melted.

Low Boiler Pressure

If your boiler has low boiler pressure, then your central heating system won’t work correctly.

1. Switch the boiler off at the mains

2. Now, wait for the system to cool down.

3. Locate the filling loop and if not already attached, secure it tightly.

4. Open the valves of the filling loop, and you’ll hear the water entering the boiler.

5. Once the pressure gauge reaches 1, turn off the valves and release the filling Loop.

Radiators not Heating Up

The most common reason for a radiator not heating up is trapped air.

1. To release the air, use a radiator key to open the bleed screw.

2. When you hear a hissing sound and water starts coming out, close the screw.

3. The radiators should now start to warm up.

Which Viessmann Boiler Problems Require An Engineer

Some boiler problems, especially those related to a gas boiler, are strictly the territory of an engineer. These include:

Burner Blockage

The burner supplies the correct amount of fuel and air to generate heat. If it gets blocked, the boiler won’t function.

Pilot Light Goes Out

If the gas supply to the boiler is being interrupted, it might be caused by a broken thermocouple. This safety device turns off the gas supply when the pilot light goes out.

Once replaced, the seals on the system need to be checked to ensure the system is safe.

Viessmann Boiler Warranty – Which Problems Are Covered?

The length of the warranty will vary with the new boiler model chosen. However, while in force, it will cover your system against manufacturing and material defects.

Usually, both parts and labour are covered. Full details of the warranty available on each model can be found here.

Do be aware that problems associated with installation are not covered. There are several other exclusions so do check you’re covered before you request a Viessmann engineer.

How Do I Reset My Viessmann Boiler?

If there’s a fault code displayed or there’s a risk from operating your boiler, it will lock out. Once repaired, you then need to reset your boiler for it to work again.

To reset the boiler, push the reset button for ten seconds. Then wait a few minutes for the boiler to light.

The location of the reset button varies between models. If it’s not obvious, check your manual or contact Viessmann Customer Service.

Do be aware that calls to the Viessmann technical team are routed to a call handling service out of hours. So we recommend getting in touch between 08.30 and 17.00.

Maintaining Your Viessmann Boiler

The Viessmann boiler service is the most important part of keeping a maintained system.

The engineer will ensure that your boiler is operating safely and check all parts for wear and tear. If you’re installing the best system boiler you want to ensure you look after it.

Maintenance tasks to keep your boiler working throughout the year include:

• Keeping air grilles clean and unobstructed.

• Keep the boiler pressure between 1.2 and 1.5 bars.

• Bleed radiators to get rid of trapped air.

When To Replace Your Viessmann Boiler

Most boilers have a lifespan of 10-15 years. But if you have to call out an engineer on a regular basis, then it may be better to opt for a new boiler.

Other signs which suggest a replacement is needed are noisy boilers or radiators, and leaks. Even the best combi boiler has to give in one day.

Energy bills are higher for older, less efficient, boilers so a replacement may not cost too much more over its lifespan.

Summary

Regular boiler servicing is the best option to avoid problems. It also reduces the risk of a carbon monoxide leak or finding yourself without heat and hot water.

If the time has come to find a new boiler, our fixed price service means you get the boiler you need with the risk of unexpected costs. check out the fantastic Viessmann 050 combi now!

Here is the Viessmann boiler fault code list

If you have a fault code one your Viessmann boiler then it is likely that you can find out what the issue is here. if you want to see the most common viessmann fault coeds then take a look at some of our guides where we have dived deeper into the issues as to help homeowners be aware of what the issues could be prior to a Gas Safe engineer attending.

• Viessmann F1 Fault Code
• Viessmann F2 Fault Code
• Viessmann F4 Fault Code
• Viessmann F5 Fault Code

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

Boiler model	Boiler fault	Diagnosis
Vitotronic 300-K with Vitotronic 200	Control mode	Communication fault, Vitotronic 100 of boiler 5-8

Viessmann Fault Code 10

Boiler model	Boiler fault	Diagnosis
Vitodens 200-W / 222-F / Vitotronic 300 / 200/ 200-H / 050/200-H / 300-K / vitocontrol-S	The boiler operates based on an outdoor temperature of 32°F / 0°C	Short circuit – Outdoor temperature sensor
Vitotronic 300-K, MW2S with Vitotronic 100 / Vitodens 100-W (combiPLUS) / 200-w / Vitocontrol-S, WB2B with Vitotronic 100	Controls as if the outdoor temperature / Constant Mode	The outdoor temperature sensor shorted out

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

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Burner in fault mode / Emergency operation	Fan not at standstill / plug-in connection

Viessmann Fault Code D4

Boiler model	Boiler fault	Diagnosis
Vitotronic 300 / Vitotronic 300-K with Vitotronic 300	Boiler cools down	Fault, safety equipment at ” X2 / X3 / X7″ of plug-in adaptor 2 for external safety equipment
Vitodens 200	Boiler operates in emergency mode (after approx. 30 min. BUS fault) OR Boiler cools down	Internal BUS fault OR Open circuit – Internal BUS connection

Viessmann Fault Code 18 and D1

Boiler model	Boiler fault	Diagnosis
Vitodens 100 / 200-W / 222-F / Vitotronic 300-K With 100 / Vitocontrol-S	The boiler operates based on the outdoor temperature of 32°F / 0°C / Constant Mode	Outdoor temperature sensor cable broken
Vitotronic / 100 / 200 / 300 / 050/200-H /300-K / Vitocontrol-S, MW1 with Vitotronic 100	Operates on basis of 32°F / 0°C outdoor temperature	Open circuit – Outdoor temperature sensor
Vitotronic 200-H / Vitotronic 300-K, MW1B with Vitotronic 300 / Vitotronic 300-K, MW2B with Vitotronic 200	Controls as if the outdoor temperature	Lead break, Outdoor temperature sensor
Vitotronic 050/200-H	Activates after 0°C / 32°F outdoor temperature	Cable break – Outdoor temperature sensor
Vitodens 100-W	Burner in fault mode	DIP switch S2 is set to “ON”

Viessmann Fault Code A4

Boiler model	Boiler fault	Diagnosis
Vitodens 222-F	Burner blocked. The venting program is started automatically	Air lock in the Internal circulation pump or minimum flow rate not achieved

Viessmann Fault Code 0C

Boiler model	Boiler fault	Diagnosis
Vitodens 100-W	Burner blocked	Insufficient power supply
Vitodens 200	Burner control switches to lockout	Flame signal still present after switching off

Viessmann Fault Code C1

Boiler model	Boiler fault	Diagnosis
Vitodens 200	Burner control unit switches to lockout (due to large line voltage fluctuations)	Differential air pressure sensor / open circuit

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

Boiler model	Boiler fault	Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitotronic 100 / 300 / Vitotronic 300-K with Vitotronic 300	Boiler cools down	fault: Maximum pressure limiter 1 2

Viessmann Fault Code 41

Boiler model	Boiler fault	Diagnosis
Vitotronic 300	Operation without accounting for return water temperature	Short circuit – Return water temperature sensor of mixing valve circuit 2

Viessmann Fault Code 88, 89, and E6

Boiler model	Boiler fault	Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitotronic 300-K with Vitotronic 100 / 200	Control mode	Communication fault, Vitotronic 100 of boiler 1-4

Viessmann Fault Code AD

Boiler model	Boiler fault	Diagnosis
Vitodens 200	Setting via service level not possible	Data points are not stored; internal fault VR20

Viessmann Fault Code F5

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Gas pressure switch shows no gas pressure / Electrical connection fault	Gas shut-off valve closed; gas pressure switch faulty; multiple problems with gas supply

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

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Boiler cools down	Fixed high limit has responded or fuse F2 has blown.

Viessmann Fault Code B4

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Normal operation / fault around burner control unit	Internal fault (PCB)

Viessmann Fault Code 80, 81, 82, 83 and FD

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Burner control unit in a fault state; system cools down; burner control unit locked out	Short circuit – Boiler water temperature sensor, burner control unit

Viessmann Fault Code B5

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Control Mode	External safety equipment

Viessmann Fault Code 19

Boiler model	Boiler fault	Diagnosis
Vitotronic 300	Activates after 0°C / 32°F outdoor temperature	Communication fault, Wireless Outdoor temperature sensor

Viessmann Fault Code B2

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Control mode	Internal electronics fault

Viessmann Fault Code 21

Boiler model	Boiler fault	Diagnosis
Vitotronic 200 / 300	operation without influence of return water temperature	Short circuit – Return water temperature sensor

Viessmann Fault Code 0b

Boiler model	Boiler fault	Diagnosis
Vitodens 200	The burner control switches to lockout. The fan does not idle after auto reset (incorrect fan rpm).	Severe wind conditions in the vent system
Vitodens 100-W	Burner blocked	Insufficient water flow. Incorrect flow direction. Defective flow switch.(Blockage)

Viessmann Fault Code FE

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Burner blocked or in fault mode	Strong interference (EMC) field nearby, or Faulty main PCB

Viessmann Fault Code 20

Boiler model	Boiler fault	Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitotronic 300 / 300-K / 200 / 100	Stand-alone control unit without supply temperature sensor (possibly supply temperature not high enough)	short circuit – Common supply temperature sensor
Vitocontrol-S with Vitotronic 100 / Vitotronic 300-K, with Vitotronic 200	Vitocontrol-S, controls in a stand-alone manner w/o supply temperature sensor (supply temperature may not be high enough)	Common supply temperature sensor shorted out
Vitocrossal 300	Regulates without supply temperature sensor (low-loss header)	Short circuit – System Flow temperature sensor
Vitodens 200-W / 222-F	Regulates without supply temperature sensor (low-loss header)	Short circuit – System supply temperature sensor
Vitotronic 050/200-H< / 200 / 200-H / 300	Mixing valve closes/ closed	Short circuit – Supply temperature sensor / mixing valve circuit M1
Vitotronic 300-K, with Vitotronic 100	Vitotronic 300-K, MW1S controls in a stand-alone manner w/o strap-on sensor (supply temperature may not be high enough)	Short circuit – Strap-on temperature sensor
Vitodens 200-W	Regulates without supply temperature sensor (low-loss header)	System supply temperature sensor shorted out

Viessmann Fault Code 55, 56 and 57

Boiler model	Boiler fault	Diagnosis
Vitotronic 300-K, with Vitotronic 200	Control mode	Maintenance or fault on Vitotronic 100 of boiler 5-8

Viessmann Fault Code EE and EF

Boiler model	Boiler fault	Diagnosis
Vitodens 100-W / 200 / 0 / Vitotronic 300	Burner blocked	Faulty Air pressure switch. Air damper (flap) stuck

Viessmann Fault Code FC

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Burner in fault mode	Gas valve faulty or faulty modulation valve control; or vent system blocked. Check fan, fan cable, PCB

Viessmann Fault Code FE4

Boiler model	Boiler fault	Diagnosis
Vitocrossal 200	Burner shuts down	Multiple detection of undervoltage

Viessmann Fault Code 10, 14, F3, and F4

Boiler model	Boiler fault	Diagnosis
Vitodens 200	Case A: Burner control unit in a fault state; system cools down; burner control unit locked out. Case B: Type of coding card	Case A: Coding card not inserted in the burner control unit; incorrect or faulty coding card. Case B: Coding card does not match burner control unit.

Viessmann Fault Code F-B7, F-F4, F-F2, F-F7, F-F8 and F-F9

Boiler model	Boiler fault	Diagnosis
Vitocrossal 200	Case A: Burner control unit in a fault state; system cools down; burner control unit locked out. Case B: Type of coding card	Case A: Coding card not inserted in the burner control unit; incorrect or faulty coding card. Case B: Coding card does not match burner control unit.

Viessmann Fault Code 50, 51, 58 and 59

Boiler model	Boiler fault	Diagnosis
Vitodens 200-W / 222-F	No DHW heating/ Fault with DHW	Short circuit/open circuit – DHW tank temperature sensor or lead break

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

Boiler model	Boiler fault	Diagnosis
Vitodens 200	Boiler cools down	Sensor inputs are not read correctly

Viessmann Fault Code 48 and 4C

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Mixing valve closes / Closed	Heating circuit 2 with mixing valve supply temperature sensor cable broken / open circuit

Viessmann Fault Code 40 and 44

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Mixing valve closes	Heating circuit 2 with mixing valve supply short circuit on temperature sensor

Viessmann Fault Code E2 and E3

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Burner blocked	Fault, supply voltage 24V

Viessmann Fault Code F-FA, F-FB and FR

Boiler model	Boiler fault	Diagnosis
Vitocrossal 200 / 400-620 / 186-311	Fan runs without demand; Burner control unit in a fault state	Fan has not stopped; cable [100A] faulty; fan faulty; burner control unit faulty

Viessmann Fault Code 60, 68, 70, 78, BD, BE and BF

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	– No output reduction – Return control open – Boiler with maximum temperature	Short/open circuit – Temperature sensor [17A]

Viessmann Fault Code 8C, 8D, 8E and 8F

Boiler model	Boiler fault	Diagnosis
Vitotronic 300	Burner control unit in a fault state	Lead break, Boiler water temperature sensor, burner control unit

Viessmann Fault Code D5

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Burner blocked	Flue gas temperature sensor not properly positioned / Check Sensor External pump fitted on the system(100-w) A-3 fault.

Viessmann Fault Code B6

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Control mode	Open circuit – KM BUS to solar control unit / Extension AM1 / DE1-DE3 M1 / communication fault

Viessmann Fault Code CC and F0

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Burner in fault mode	Ionisation current too high during calibration Boiler temperature limiter responded(F2) air or blockage in system/pump failure

Viessmann Fault Code 52

Boiler model	Boiler fault	Diagnosis
Vitotronic 300	Control mode	Short circuit – Supply temperature sensor low-loss header
Vitodens 100-W CombiPLUS	Burner blocked (with CombiPLUS only)	Flow sensor shorted out (in CombiPLUS)

Viessmann Fault Code 5A, B7, and B8

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Control mode	Lead break, low-loss header Supply temperature sensor
All Viessmann boilers	Burner blocked / control mode	sensor cable broken

Viessmann Fault Code 38

Boiler model	Boiler fault	Diagnosis
Vitodens – 200-W / 222-F / COMBIPLUS	Burner blocked	Boiler water temperature sensor cable broken
Vitotronic 100 / 200 / 300 / Vitocontrol-S with Vitotronic 100	Burner is switched on and off by the adjustable high limit	Open circuit – Boiler temperature sensor
Vitotronic 300-K with Vitotronic 300 / Vitotronic 300-K with Vitotronic 300	The burner is started and stopped via a temperature controller	Lead break, Boiler water temperature sensor
Vitodens 100-W	Burner blocked	Boiler water temperature sensor lead broken

Viessmann Fault Code A7

Boiler model	Boiler fault	Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitotronic 100 / Vitotronic 300-K with Vitotronic 300	Control mode	Isolation valve configuration fault: Coding OC:2, OC:3 or OC:4 set, and coding 4E:1 not set

Viessmann Fault Code C9, CA and CB

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Boiler drives up to electronic maximum limit	Boiler does not log in at the cascade control unit

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

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Control mode	Short circuit – Temperature sensor

Viessmann Fault Code 0F

Boiler model	Boiler fault	Diagnosis
Vitodens 222-F	Control mode	Code ”0F” is only displayed in the fault history(service required)
Vitotronic 300 / Vitotronic 300-K, with Vitotronic 300 / Vitodens 200-W / Vitocontrol-S, with Vitotronic 100	Control mode / Controlled operation	Service required. ”0F” is only displayed in the fault history.
Vitotronic 200 / 300	Normal operation	Service required
Vitocontrol-S, MW1 with Vitotronic 100 / Vitotronic 300-K, MW1S with Vitotronic 100	Control mode	Maintenance ”0F” is only displayed in the fault history

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

Boiler model	Boiler fault	Diagnosis
Vitodens 200-W / 222-F / Vitotronic 300	Burner in fault mode	Heating water flow rate too low during calibration; flow switch caused shutdown

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

Boiler model	Boiler fault	Diagnosis
Vitotronic 200 / 300	Normal operation without influence of return water temperature	Open circuit 1 or 2 – Return water temperature sensor (of mixing valve circuit 1)

Viessmann Fault Code A3, B0, F1, F-E1 and F-E2

Boiler model	Boiler fault	Diagnosis
Vitocrossal 300 / Vitodens 200-W / 222-F / 300	Control mode (stays in factory default setting)	Faulty Programming unit

Viessmann Fault Code 28

Boiler model	Boiler fault	Diagnosis
Vitocontrol-S with Vitotronic 100	Vitocontrol-S, VD2/CT3/CM2 controls in a stand-alone manner w/o supply temperature sensor (supply temperature may not be high enough)	Open circuit – Common supply temperature sensor
Vitocontrol-S with Vitotronic 100 / Vitotronic 300-K,with Vitotronic 100	Vitocontrol-S, WB2B controls in a stand-alone manner w/o supply temperature sensor (supply temperature may not be high enough)	Common supply temperature sensor cable broken
Vitocrossal 300 / Vitodens 200-W / 22-F	Regulates without supply temperature sensor (low-loss header)	System supply temperature sensor cable broken
Vitotronic 050/200-H	Mixing valve closes	Cable break – Supply temperature sensor
Vitotronic 050/200-H	Mixing valve is closed	Open circuit – Supply temperature sensor of mixing valve circuit M1
Vitotronic 200-H / Vitotronic 200 / 300	Mixing valve is being closed	Lead break, Supply temperature sensor, heating circuit with mixing valve M1 (heating circuit 1)
Vitotronic 300 Vitotronic / 300-K with Vitotronic 300 / 200	Stand-alone control unit without supply temperature sensor (possibly supply temperature not high enough)	Lead break, Common supply temperature sensor
Vitotronic 300-K with Vitotronic 100	Vitotronic 300-K, MW1S controls in a stand-alone manner w/o strap-on sensor (supply temperature may not be high enough)	Open circuit – Strap-on temperature sensor

Viessmann Fault Code B1

Boiler model	Boiler fault	Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitotronic 100 / 200 / 300 / Vitotronic 300-K with Vitotronic 100	Emissions test mode	Internal electronics fault
Vitocontrol-S with Vitotronic 100 / Vitodens 200-W	Regulates as if the outside temperature was 32°F (0°C)	Internal fault
Vitotronic 200 / 300	Normal operation	Service required
Vitotronic 050/200-H	Undefined control characteristics	Internal electronics fault

Viessmann Fault Code E4

Boiler model	Boiler fault	Diagnosis
Vitocontrol-S with Vitotronic 100 / Vitocrossal 300 / Vitodens 200-W / 222-F / Vitotronic 300	Burner in fault mode	At burner start, flame signal is missing or too weak

Viessmann Fault Code A8

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Control mode	Communication fault, Programming unit

Viessmann Fault Code FA and FB

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Control mode	Communication fault

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

Boiler model	Boiler fault	Diagnosis
Vitodens 200	Pump runs at maximum speed	Open circuit – BUS connection with variable speed heating circuit pump

Viessmann Fault Code B3 and E5

Boiler model	Boiler fault	Diagnosis
All Viessmann boilers	Constant mode	Invalid hardware recognised

Viessmann Fault Code 30

Boiler model	Boiler fault	Diagnosis
Vitocontrol-S, with Vitotronic 100 / Vitocrossal 300 / Vitodens 200-W / 222-F / Vitotronic 100 / 200 / 300	Burner is started and stopped via an adjustable high limit	Short circuit – Boiler water temperature sensor
Vitocontrol-S with Vitotronic 100 / Vitodens 100-W (CombiPLUS)/ 200-1	Burner blocked	Boiler water temperature sensor shorted out