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Ask The Trades › DIY Forum › Plumbing Questions › Boiler size

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Boiler size (Read 3108 times)

ckelly0172

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Boiler size
May 24^th, 2014, 12:12pm

Hi, appreciate a little advise please.

I'm in the process of replacing my central heating system and am a bit confused with calcualting the boiler size. I have 4 bed detached with 1 bath, 3 shower (2 electric), BTU calcs equate to approx 38,000BTU (+2000 for water)

To calculate what boiler is it a case of coverting the BTU to W, in that case it's 11KW which just appears too low.

Any help really appreciated.
Thanks
Craig

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thescruff

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Re: Boiler size
Reply #1 - May 24^th, 2014, 2:45pm

A lot depends on the insulation properties, double/triple galzing etc, the more heat you can keep in the better.

If you numbers are correct go for an 18kw or maybe slightly larger if you plan any work in the future, all modern boilers can be range rated down to suit the actual load. Plus if you consider open therm, weather compensation etc the boiler/system will be infinitely controllable

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ckelly0172

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Re: Boiler size
Reply #2 - May 24^th, 2014, 3:21pm

Thanks scruff, I calculated my radiator BTU's using standard requirements on online calculators, all rooms equated to 40K btu. Have cavity insulation and 270mm in the loft, all relatively new double glazed.

All advice online for a 4 bed detached seems to point towards 35-42 KW bolier, and that's why I'm confused as my BTU totals to 12KW?? Will have 13 radiators by my reckoning. Kitchen, Lounge x2, hall, Dining, Family, x4 bed, x2 ensuite, bath.

Just to make sure I'm correct, when using the online calculators, i do match the results for each room with that of the radiator output?
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thescruff

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Re: Boiler size
Reply #3 - May 24^th, 2014, 4:55pm

Add the total kw/Btus of all the rads will give you a rought idea.

Post the external length and width of the property plus ceiling heights and I'll check it out.

Are they wooden suspended floors or concrete.

Another factor is location, the further north the colder it gets, supposedly.

I'm out tonight but will check it later if you post the information.

« Last Edit: May 24^th, 2014, 4:56pm by thescruff »

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ckelly0172 Junior Member Offline Posts: 45 Total Thanks: 0 For This Post: 0 Gender:	Re: Boiler size Reply #4 - May 25^th, 2014, 7:01pm Cheers, 11m x 10m wih internal garage 2.4m ceiling downstairs, 2.2 upstairs Suspended wooden floors In Huddersfield, so not that far north, but far enough some will say..!
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thescruff Global Moderator Trade Member Author Offline Who said plumbing was easy. Posts: 6037 Total Thanks: 147 For This Post: 0 Gender: Trade: Plumber	Re: Boiler size Reply #5 - May 25^th, 2014, 11:00pm Hi, Comes out at 13.4 Kw. Go for 18Kw and range rate it, your RGI should be able to do that, and give you a bit more for the hot water. Note; the above allowed for 40²m of glass
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