Sizing of a new boiler-is the advice I'm being given correct

[sb13471]

Gents,
During a recent 'Service', our boiler was condemed


We have a medium size 4 bedroom detatched house, with 10 rooms over 3 floors (including 2 bathrooms), 11 Rads (3 of which are doubles) and 11 sash windows plus the conservatory, which is half glass (6 windows and a polyboard roof)


Now I do realise that the old boiler was only about 16 Kw but the heating engineer wants to replace it with a Worcester greenstar 18 RDI...which to me means doing a like for like - no brainer kind of sizing for the new boiler, but from what little research i have done I get the feeling that this is not really adequte for a couple of reasons.

Firstly - I heard the heating engineer who switch off our old boiler tell him that ' for a house of this size- you'd need about a 24kw'er'......and since then I have called a heating supplier who estimated the exact same size over the phone based on the little information I gave them- as above.
i know its not accurate...but ballpark is good enough to confirm my concerns?

I'm concerned that although I have expressed this opinion but that he is still insisting that the boiler will be more than 'adequate' as it's moe powerful than our old boiler.

That may be the case but our old boiler never really gave the house a tropical feel......

I can't help thinking he's offloading a boiler he has in stock as I have said I am willing to pay extra for something a bit more manly. but he won't entertain it.

Any comments/advice on size would be more than welcome

 

[Agile]

I expect an 18 kW would be quite adequate.

However any professional installer would calculate the heat loss of the house with the whole house method and also work out the heat output of your rads.

Now the weather is cold he could also measure the indoor temperature and the boiler input power required to achieve that.

Knowing what I do about the heating industry I would never let someone who had condemed replace it unless I had a second opinion about the need to condem it and the price of installing a replacement.

Why not ask for a quote for fitting a Viessmann boiler which has a five year guarantee when fitted by an approved installer !!!

Tony

 

[kirkgas]

it definately looks as if he has a boiler to offload, as others have said get details of why it is condemned and get a second opinion

 

[D_Hailsham]

However any professional installer would calculate the heat loss of the house with the whole house method

Recommended Boiler Size Calculator

work out the heat output of your rads.

The Stelrad Elite Catalogue is a good starting point for estimating rad output.

 

[sb13471]

Guys,

Advice much appreciated.

Although I have no idea if the boiler was genuinely on its way out, It was the original one that was installed when the house was built over 25 years ago (potterton Netaheat- which I understand was top drawer in its day)
Apparently the heat cell was badly corroded and and he put his finger through it while inspecting it ....when it comes out I will take a look myself.

His wife is a very good friend of my partner and when we have work done in the past they he has always been pretty straight with us and reasonably priced.

I'm a engineer myself (Industrial control systems), so took the precaution of doing a couple of calcs. I have measured up all my rads and used Heat loss calculators off the Net (I know they're not the greatest)...the results were quite telling.
Approx 14 KW of heat loss, and My rads size up to just over 20 KW worth.

I tried to get a second opinion from British Gas.......they cant send someone around until the 7th November

I told him about my calcs this morning and he called me back to say that he can fit a 24KW instead...A greenstar Ri though still, not the 30 CDI which I originally suggested that I'd prefer after a little reading up- as he says that would still be too big.

I feel alot better now we have reached a compromise. the price is in the correct ballpark from what I can tell and as I'm getting it in the neck from the missus about it being 'freezing' it's going to be fitted on Monday.


Thanks again!