Vaillant eco TEC plus 418 coming on outside timed hours

[PaulGeyser]

Just to add belatedly, when your Vaillant boiler does something unexpected like this then press the top two buttons to display the status code whilst it's doing it. Mine also runs the fan for a few seconds now and then and the status code is S.108, which from the manual means "
Purging the combustion chamber, fan in operation". Of course whether this is accurate and if so why would it need purging is anybody's guess...

 

[Harry Bloomfield]

Just to add belatedly, when your Vaillant boiler does something unexpected like this then press the top two buttons to display the status code whilst it's doing it. Mine also runs the fan for a few seconds now and then and the status code is S.108, which from the manual means "
Purging the combustion chamber, fan in operation". Of course whether this is accurate and if so why would it need purging is anybody's guess...

The combustion chamber purge, happens every time, just before it fires - it probably does it (runs the air fan) for safety, to ensure there is no gas in there, and to ensure the fan is able to run.

It also runs the fan (and the pump?) briefly, every 24 hours to help avoid them seizing.

 

[PaulGeyser]

Sure, but I meant why would it do this when not firing up and when it has fired up within the last few hours. Just a bug I suspect.

 

[Harry Bloomfield]

Sure, but I meant why would it do this when not firing up and when it has fired up within the last few hours. Just a bug I suspect.

When our Vaillant was installed, I noticed the fan start up, asked Vaillant UK about it, and they simply were not aware that it did it, or why it might do it.

I also thought I spotted the 470f controller, retaining as permanent settings, temporary changes in temperature from the day before, without my pressing the OK button to store the new temperature. I only recently found out I was wrong about this - it was the display which 'hung onto' the last temperature setting it had been called upon to display. Activating the display a second time, caused the display to update with the correct data.