Which boiler

[Reltub]

Hi guys I have been asked to quote for new radiators in a very large house - 6 beds 1 main bathroom 1 on-suite and 1 downstairs toilet.
There are currently 13 rads on the system and will be 15 with the 2 they want adding on. The boiler thats currently in is a main 30kw combi.
Ive worked all the rads out to have a combined output of roughly 32kw. (Some very big rads)
Ive been looking at the worcester 42kw cdi with a ch output of 30kw.
What i want to know is will this size boiler be able to cope with the demand, if no recommendations for what will would be appreciated.
Also will 22mm pipe runs be sufficient.

Thanks

 

[Simon F]

the issue is demand for hot water

 

[Reltub]

The hot water output from the 42kw boiler for be fine for the customers needs I just want to confirm that this boiler will be able to handle the central heating demand.

 

[Mike Jackson]

If the rads need 32kw and the 42Cdi gives 30 then it's not enough. look at Atag boilers they do a 51 Kw combi.


Sent from my iPad using Tapatalk HD

 

[Reltub]

£2750!? Doubt they'll go for that mate

 

[Barry98]

What they need , want and can afford are all differny things

 

[Reltub]

They sure are I think ill just gor for the 42kw Bosch.

 

[SafeGasInstall]

go for wb heat only 40CDi and install a UHWC , they will love you for the rest of there live

 

[ecowarm]

Size the house not the existing rads as will be over sized anyway

 

[Reltub]

Haha i know mate its just the £ issue and they only originally budgeted for swapping the rads.

 

[Reltub]

I have sized the house and all existing rads are massively undersized the 32kw is the rads im going to be fitting I think i should be ok with the 42kw boiler as the 3 top floor rads are rarely used, if i did fit it will i get away with just connecting onto the exisiting 22mm htg pipes.

 

[ecowarm]

existing rads Masively undersized? With an output of 32KW and you want to put in a boiler with a max output of 30kw? Something not quite right there. How did you do the whole house sizing

 

[Reltub]

No mate with the correct size rads for the house it's 32kw and the top floor rads are rarely useds so with out them its roughly 28kw output.

 

[Mike Jackson]

I hope that you are going to put in writing that you are supplying a boiler that will not cope with the maximum demand of the system. If not when they get guests you will have an irate customer on the phone telling you that the system you've put in doesn't work.

 

[doitmyself]

How did you do the whole house sizing

Could we have an answer please?

 

[Reltub]

Measured rooms and put calcs into Radiator Sizing Calculator in KWh and BTU which gave me the kw of each rad.

 

[Howsie]

I've said it once and I'll say it again. Read the Domestic Heating Design Guide and you'll be fine.

 

[Howsie]

Domestic Heating Design Guide.

 

[Howsie]

Bloody phone !!

 

[doitmyself]

Measured rooms and put calcs into Radiator Sizing Calculator in KWh and BTU which gave me the kw of each rad.

Wouldn't trust that site as it does not give any information about the basis of its calculations, such as assumed U values, size and type of windows etc.

Use the Whole House Boiler Size Calculator to find out what size boiler is required. Then compare this to the total output of the existing rads.