Boiler Size

[sh4d0w]

Hi All.

I was just about to order myself a Vaillant Eco 637 boiler for the new house but as i was about to checkout i noticed the heat output was 120,000 BTU, by my calculations and over measurements of each room i require 50,000 BTU, that is based on me rounding up to the nearest 1000 per room and adding a bit more. In total ill have 16 Rads.

I have 2 bathrooms and will be splitting into two zones etc.

Using the Vaillant online calculator it recommends the 637 with the 630 next in line.

Is there any benefit in my having the 637 when on paper i dont require it so to speak?

PS, im no plumber, my bother is a gas safe installer and is doing the fit for me but i need to make sure i buy the right kit.

 

[Dan Robinson]

A 637 would be bonkers.

a 628 would be the biggest I would consider but would probably plumb for either a 618 or 624.

 

[sh4d0w]

Hi,

thanks for the response, can you tell me why a 637 will be bonkers?

for a rough idea, the house a large 4 bed 2 bath semi-det house.

 

[D_Hailsham]

I was just about to order myself a Vaillant Eco 637 boiler for the new house

I assume you mean new to you not a new build.

Use Baxi Whole House Boiler Size Calculator to find out what size boiler is required. (It uses standard data produced by the Building Research Establishment.)

 

[muggles]

A 637 will cost much more to run, as well as being more expensive to buy. You should get a boiler that is the right size for your house. You'd probably also be better off letting your installer get it for you as they'll almost certainly be able to obtain it at a better price than you can

 

[Dan Robinson]

You said you only needed 50000btu

that's 14kW.

And that is when is is sub zero outside.


Why pay more for a boiler that is over sized.

It will spend more of its life turning on and off. Causing wear and tear.


Several posts recently where people are unhappy with the performance of their Vaillant because it is not sized correctly.


My 4 bed detached house with bathroom and ensuite using LOTS of hot water only has a 15ishkW boiler fitted and despite having one of the cleverest control systems on the market installed I still can't stop the bugger cycling on and off.

 

[sh4d0w]

thanks guys. I will go over that calculator again, i did it briefly before and it came out at 17.4KW, but it was a really rough guess. I just thought a larger boiler would need to run less equaling lower running costs... well, thats what thinking did for me! lol.

Ill be going with an Albion 210l Cylinder

 

[Dan Robinson]

I have a 300 odd litre thermal store for hot water.

You logic is not uncommon, but totally arse about face. Don't feel bad though.

 

[sh4d0w]

its now looking more like the 624! that is still a little over sized based on my calculations but will allow for expansion in the future.

As for buying the boiler, ill buy it offline as it appears that its miles cheaper than my brother can get it via Plumbase.