Viessmann vitodens 100

[ndsmith]

Been to a vitodens 100 that is warming up and shutting off quite quick, the pump is spinning and adjusting speed no problem however heat isn't being transferred to rads or cylinder.

This vitodens model is the earlier one without the air vent on off heat exchanger , I'm starting to think it might be air trapped in there , although it's not kettling.

Any ideas on best way forward with it, i.e. Best way to vent the heat exchanger

thanks

 

[ShaunCorbs]

whats temp doing sounds like you dont have any flow through the boiler

 

[ndsmith]

Temp is warming up to where you want it low or max but just not circulating.

 

[ShaunCorbs]

whats the drain at the top of the hx doing when opened?

 

[ndsmith]

There isn't one on this model, I think it is one of early ones

 

[townfanjon]

I gather this is a heat only 100

 

[ndsmith]

Sorry yes. Heat only , open vent

 

[townfanjon]

Silly question nothing daft like a nact 2 ports is it.

The only thing I have ever gone to on one of these was a knact flowswitch, but if the pump stops / starts it shouldnt be that . Any recent works been done ?

 

[ndsmith]

On a 3 port which is working fine.

3 months ago I worked on system bled it all and been working fine since then until yesterday

 

[ndsmith]

I have sorted this now, it was air trapped at the top of the heat exchanger.

Early viessmanns like this one don't have a vent on top, so if possible and have a drain off on the RETURN pipe above the boiler, close off a pump valve and drain off from the return pipe so that the cold feed goes through the boiler and run until air is out, ensuring that the header tank is obviously being filled up so you aren't dragging more air through.

Nice one to remember for you all hopefully.

Thanks