Viessmann · Selected Vitodens and Vitotronic ranges
5C / 5D / 5E / 5FCommunication fault with Vitotronic 100 on boiler 5–8
This code applies to Vitodens 100-W, Vitodens 200-W, Vitodens 222-F, Vitotronic 100, Vitotronic 200, Vitotronic 200-H, Vitotronic 300, Vitotronic 300-K, Vitocontrol-S. Fault codes narrow down the likely problem, but they do not replace a model-specific diagnosis.
What you can safely check
- Power-cycle or reset once only if the user manual specifically permits it.
- If the message remains, arrange an engineer.
How an engineer may fix it
Check configuration, coding, communication buses, plugs, wiring, power supply and control boards; configure, repair or replace the failed control component.
Viessmann warns that the same code can have different meanings on different models. The exact manual must take precedence.
Manufacturer source: Viessmann UK — Fault Code Checker. Checked 15 August 2026. The appliance manual and an engineer’s on-site diagnosis take precedence. Never remove the boiler case yourself.