Quick guides to boiler and radiator sizing

[mutley racers]

Hi guys, just wondering if any of you have any rules of thumb for the sizing of radiators and boilers.

Dont like all the calculations. So if there is a way i can get by without all the U values and Heat loss calculations. If not, then i shall have to stick with them.

Thanks for all your knowledge.

Mutley

 

[Boyler]

i would normally just measure each room in feet (length x height x width and multiply that by 5 to get the btu's) do that for each room to get the size of each radiator, then add them all up to get the size of boiler. to convert that to kw divide btu's by 3412 or 3142 cant be to sure on that one. well thats what i do anyway. and add about 3 kw for heating of cylinder

 

[mutley racers]

Thanks boyler. That is excellent.

 

[Bernie2]

Yes the rule of thumb Boyler suggests is well known. But if you want to be a bit more scientific "Google" Stelrad "Stars" and download their sizing program. Its nice and easy to use, no maths either and you can muck about with different rad sizes.

Good fun. I have used it for sizing and it works great Its Free by the way.

 

[tamz]

Big room, big radiator

Get yourself a Mears calculator and work out a full house in under 5 minutes.

 

[doitmyself]

As well as using Sterad Stars, you should use the Boiler Size Calculator to check that your calculations are correct.

Don't forget that, if you over-size your radiators, you will be able to run at lower temperatures, which saves fuel. For example, if you run with a flow temperature of 75C and return temp of 55C, you will need to oversize your rads by 20%; and if you run at 65C/55C, you will have to oversize rads by35%. This does not affect the size of boiler.

If you are installing a combi boiler, the boiler size is determined by the hot water requirements. But it's worth checking that the heating requirement is not below the lower modulation limit of the proposed boiler. Ideally the lower limit should be well below the calculated heating requirement as it means the boiler will be able to modulate down when the outside temperature is higher.

If you don't want to go to the bother of using Stelrad Stars, find the boiler size using the boiler calculator. Then divide this between the rooms based on floor area. If you want to you can give more to the ground floor rooms as they tend to need a higher temperature than the bedrooms.