Replacement boiler - help needed

[RedBus]

Hello all, this is my first post.

I have a four bedroom house on two floors. Three toilets, 1 bath and two showers (1 electric, the other on mains supply), oh and four children. The current boiler is an old Vaillant 24kw combi (about 20 years old) that has now passed away to boiler heaven.

I have 13 radiators all with TRV's.

I have 4 bar of pressure with a flow rate of 14 to 15 Litres per minute.

I see my basic? option of changing the existing Combi for a newer bigger model, top three listings are:-
Viessmann Vitodens 200W-35kw Combi.
Worcester Bosch Green star 37 CDI.
Vaillant Ecotec Exclusive 838.

I also want the Weather compensator controls and all three of the above, you can spec with an option for this.

IF I choose the correct installer for either the viessman or the Worcester Bosch, the Boiler warranty goes from 3 to 5 years.

So basic question is, for the details above, which one would I be advised to buy more?

The next level gets a bit tricker as I have also been advised to put a System boiler in with a pressursied tank. Can the advantages of this over the above Combi's for my house above be explained by any one?

Thank you in advance.

 

[doitall]

If a combi serves your needs now, it should be fine with the new more powerfull one.

From your list I would Go.

1st Broag Avanta.

2nd WB CDi