Viessman any good

[rhinosaw]

I have heard good things about the above, is that correct?
I currently have an old vented 12 kw boiler and have been quoted for a 19kw Vitodens , 100 system boiler.
Would going for the 11kw be ok as they don't seem to do anything in between
Thanks

 

[John the plumber]

I have heard good things about the above, is that correct?
I currently have an old vented 12 kw boiler and have been quoted for a 19kw Vitodens , 100 system boiler.
Would going for the 11kw be ok as they don't seem to do anything in between
Thanks

You will always get mixed answers regarding boilers,some will say viessman boilers are good some will say they aren’t.

 

[Notch7]

Ive heard parts are dear and support isnt terribly good in the UK

intergas boilers used to be highly recommended on here, not sure if they are now.

 

[JohnD]

At the time I bought mine, they were praised here. I particularly wanted the stainless heat exchanger.

people say parts are not widely stocked but sent out from the main depot when needed. I would be more suspicious of a boiler that broke down so often that parts were sold on every high street.

I have not needed any parts in 15 years, though I had a free replacement air flap fitted under warranty.

A more powerful boiler can modulate down (flame size reduced), but a less powerful boiler can't be made more powerful, so I'd prefer the 19.

 

[rhinosaw]

Thanks John
Is the 19kw as likely to run on a 15mm feed as the 11kw? No other gas appliances in flat by the way

 

[Mottie]

I would have thought a modern 11kw boiler as a replacement for an old 12kw one in a flat would be more than capable. As said, if going for a 19kw, check what it modulates down to. We have an 18Kw in a 3 bed semi and I only run that at 15kw max. Did you have a heat loss calculation done to determine what size boiler you actually need?

 

[MeldrewsMate]

Thanks John
Is the 19kw as likely to run on a 15mm feed as the 11kw? No other gas appliances in flat by the way

No...or maybe no.
The pipesize needed is a function of its length, the number if bends, and the expected maximum gas flow. A 19kW boiler will need almost twice the gas flow an 11kW boiler needs.

Empirically speaking, does your present 12kW boiler get each and every radiator up to full temperature?
Is this enough to heat the flat to your requirements?
When hot, what proportion of each hour does the boiler run? 100%? If less than 90% then it is highly likely that an 11kW boiler will be adequate...

I'd still urge you to buy a boiler that's made in Britain though.

 

[rhinosaw]

No Mottie.
No heat loss calculation done, not sure what that involves.
Just thought that 19kw in a flat may not be needed as 12kw was ok before

 

[rhinosaw]

MM thanks
Flat used to be hot enough on 12kw , didn't really want to change feed to 22/28 unless really necessary

 

[muggles]

I'd still urge you to buy a boiler that's made in Britain though.

You'll struggle to find one though. Assembled here from components made elsewhere is the closest you'll get, and their owners aren't based here

 

[muggles]

MM thanks
Flat used to be hot enough on 12kw , didn't really want to change feed to 22/28 unless really necessary

If your flat does fine with an ancient 12kW then a modern 11kW Viessmann will work just fine. Stick an OpenTherm roomstat on it for best efficency

 

[Gasguru]

No boilers are truly "manufactured" in this country but several models are assembled from parts sourced globally.
So you should ignore boiler manufacturers websites regarding their manufacture...they are largely a work of fiction.
A huge amount of re-badging goes on with boilers being manufactured/assembled abroad and imported directly here.
For example Baxi were once re-badging Chaffoteauxs and Ideal re-badging Biasis. Baxi are currently re-badging Remehas (they are part of the group).
One of the more immoral manufacturers is also a member of a "UK manufacturing" organisation to promode the "Made in Britain" boast whilst offshoring most of the manufactured parts and onshoring the assembly.

 

[rhinosaw]

Thanks GG
Still trying to work out 11kw v 19kw .
If the 11k works from a 15mm feed will the 19kw or not necessarily. Installer says 19kw the right one to fit.
Technical at veissman said both the same, is that possible

 

[muggles]

Thanks GG
Still trying to work out 11kw v 19kw .
If the 11k works from a 15mm feed will the 19kw or not necessarily. Installer says 19kw the right one to fit.
Technical at veissman said both the same, is that possible

No. Higher power needs more gas, so often needs an increase in pipe size. Suggest your installer is wrong, but a proper heat loss calculation will confirm

 

[rhinosaw]

thanks Muggles

Its the technical dept at Viessman that r saying no difference in 11kw and 19kw so both will work off 15mm feed.

the installer is insisting that 19kw is the correct boiler size regardless of the fact that my current vented boiler is 11k and no heat loss calc done