Veismann vitodens boiler problem

[Chablis]

We have a newly installed Veismann boiler, our central heating works OK, but we cannot have hot water at the same time. It will only heat water but will not switch over to run the radiators. When our installer has tried to run the sytem as it is designed he can't make it work. We get Error messages saying F2. He has tried to get rid of the air in the system by venting the boiler several times but this does not solve the problem.
For the last couple of months we are using the boiler to run our radiators and we rely on the emmersion heater to heat our domestic hot water.
Can anyone suggest a solution please?

Thank you Simon for responding. It is a sealed system 4 pipe - Vitodens 100

 

[simond]

Rather a lot of options here........

Vitodens 100, 200?
Combi, system or open vent? I guess its going to be a system or open vent (Compact WB1B) because you have an immersion heater.

Are you really saying that your installer put this thing in two months ago and you still don't get hot water??????

I'd love to know what made you choose him in preference to everyone else?

 

[Chablis]

Thank you Simon, I have amended my original message as I am a new user . The Boiler is a sealed system / 4 pipe Vitodens 100.
Any furthe advice please?

 

[simond]

In the 100 there is an internal diverter valve that selects heating or hot water.

F2 is an overheat which means there is no circulation of water, presumably in HW mode only. Therefore there is an airlock, or an obstruction.

One presumes the old boiler was a 4 pipe with a gravity HW circuit?

The old cold feed and open vent would have been removed?

Is there an auto airvent on the cylinder primaries at the highest point?

 

[Chablis]

Thank you Simon.
You have presumed correctly regarding our old boiler and that the old cold feed and open vent have been taken out.
The cylinder has been fitted with an air vent.
Our fitter is planning to call Vitodens on Monday to discuss how to address the airlock/obstruction. He has tried this several times.
I asked him if it is anything to do with the wiring of the time clock as the electrician reinstalled our existing Horssman clock, we would not have objected to the fitting of a new clock. He appeared unsure.
When he has attempted to solve the problem we have difficulty getting the central heating working again as the boiler is too hot.
He has now got our heating back at the expense of hot water. But with snow forecast for next week we want to be warm and as I said we can use the emmersion heater. We are trying to help him to solve the problem but it is a worry when things dont work as expected.
Thank you so much for taking the time to offer advice.

 

[Kev F]

It works on hot water priority, so when hw is called for it concentrates solely on that, if it's a sealed system you shouldn't have an air issue, try turning the stat up to max for hw or take out the probe if used instead and let it run, also he needs to make sure the air vent on the pump is open whilst bleeding. Never get many issues with these.

 

[mysteryman]

If you have a 2 port valve on the cylinder primaries, check that it is always open when the boiler is heating the cylinder. Wiring errors are possible here.

 

[Kev F]

If you have a 2 port anywhere that's where your going wrong on the 4 pipe, no controls apart from prog stat and cylinder sensor needed

 

[Agile]

Is an unvented permitted WITHOUT a spring return motor valve on the primary activated by an o/h stat on the cylinder?

 

[Kev F]

Viessmann allow it as the boiler on max won't run above 90c

 

[ALEC1]

Yes Tony, two port valves on UVHWSS are not necessary with modern condensing boilers that have an over heat stat on the boiler..

 

[Razor900]

I thought they only allowed it with a Veissman cylinder??

 

[Kev F]

There's a little debate at the minute where they say it doesn't make any differance which cylinder, let's be fair all unventeds are the same

 

[Kev F]

You can actually still wire it so the over heat stat kills the power to boiler, then you cover all g3 without zone valves

 

[doitall]

But is it all wRas approved and why not.