Viessmann boilers covered
Viessmann is a German manufacturer, and its Vitodens wall-hung condensing boilers are fitted in a growing number of UK homes. The guidance on this page applies to the main ranges you are likely to find:
- Vitodens 050-W, the entry-level combi, often fitted in flats and smaller houses.
- Vitodens 100-W, the most common range, available as a combi and as a system boiler.
- Vitodens 111-W, a combi with a built-in hot water store for stronger hot water flow.
- Vitodens 200-W, the premium range, with a wider output range and more advanced controls.
Fault codes are broadly shared across these ranges, but the display, buttons and some codes differ between models and generations. Always check a code against the manual for your exact boiler.
How fault codes appear on a Vitodens
On most Vitodens models a fault shows as a warning symbol on the display with a two-character code next to it, such as F4 or F2. Some codes are numbers, such as 30 or 38, and some mix letters and numbers. On the Vitodens 100-W, a flashing fault symbol with the letter R means the burner has locked out and needs a manual reset. On some models the code may show in lower case, so FD can appear as "Fd".
Write the code down exactly as it appears before you do anything else. The engineer will ask for it, and it tells them which part of the boiler to look at first.
How to reset a Viessmann boiler safely
The reset method depends on the model. On the current Vitodens 100-W you press and hold the R button for about two seconds. On some Vitodens 050-W models you press two buttons at the same time, as shown in the user manual. Newer boilers with a larger display may use a menu option instead.
- Deal with any obvious cause first, such as low pressure, no gas or a frozen condensate pipe.
- Reset once and give the boiler a few minutes to try to light.
- Stop after two or three attempts. If the code keeps coming back, call a Gas Safe registered engineer.
Never remove the casing. Everything behind the front panel is a job for a qualified engineer.
Checking the pressure
Vitodens boilers have a pressure gauge, either a dial on the underside or a reading on the display. With the heating cold, most sealed systems should sit at around 1 to 1.5 bar, although your installer may have noted a specific figure in the manual. Low pressure can stop the boiler and lead to overheating faults such as F2. Our guide on how to repressurise a boiler explains how to use the filling loop.
Common winter faults
A frozen condensate pipe is the classic cold weather problem. Water backs up inside the boiler and the burner cannot run properly, which on Vitodens boilers often shows as F4, the no flame signal fault. Viessmann lists the condensate drain among the checks for F4. Thaw the pipe with warm (not boiling) water or a hot water bottle, then reset. Our frozen condensate pipe guide covers this step by step.
Viessmann fault codes we cover
- F4: no flame signal, often a gas supply or condensate problem.
- F2: temperature limiter has tripped, the boiler has overheated.
- F9: fan speed too low during burner start.
- FD: burner control unit fault.
When to call an engineer
If you smell gas, turn off the supply at the meter if it is safe to do so, open doors and windows, and call the National Gas Emergency Service on 0800 111 999. Do not use electrical switches.
Call a Gas Safe registered engineer if a code returns after two or three resets, if you need to top up the pressure often, or if water is leaking from the boiler. A yearly service catches many faults early, and our boiler service cost guide explains what it typically costs.