Viessmann vitodens 050 error f4
The error code F4 is an indication of the time lost between cycles.
In general, a water heater’s heat exchanger can be clogged with mineral deposits or lime, resulting in higher-than-normal heat loss and decreased efficiency of the water heating unit. Common causes for clogging are: using the wrong type of water in the tank; not properly maintaining the tank according to manufacturer’s specifications (nearly empty tank); improper installation (gas connections not sealed); prolonged use without cleaning.
Steps to troubleshoot:
Turn off the power to the water heater.
Disconnect the gas supply and drain as necessary.
Remove and clean/replace components as needed until the problem is resolved.
There are many possible causes for the error F4. However, most of them can be eliminated by ensuring that the heating system is operating and that the board is properly positioned in its slot.
The problem is not a failure of the thermostat.
The problem is the failure of the boiler.