Roger Mills wrote:

"bodger" wrote in message
om...

Hi. Our old Rayburn multifuel cooker/boiler just died, and I need to
replace it with something else. The rayburn used to run a central
heating system of 13 radiators with a total area of approx 12 square
yds; 9.6 square metres.

Can anyone tell me what Btu output figure the replacement stove should
have to run the existing radiators comfortably? Or where on the web I
could find the formula to work it out for myself?!

Many thanks.


In the 1970's, when radiators didn't have fins - like they do today - a
rough figure was 180 BThU/Hr per square foot of surface area.

I'm not sure whether your 12 sq yds is just one side of each rad, or both
sides. If it is just one side, you need to double it to get surface area -
and the above formula then gives a heat output of just under 40,000 BThU/Hr.
If any of the radiators are doubled, or finned, they will have a higher
output and you will need to take this into account when sizing a replacement
boiler. Does your boiler also need to provide domestic hot water? If so, add
a further 15,000-20,000 BThU/Hr.



NOTE: This does not compute if you have a hot water tank. You need very
little to heat a tank - maybe 500-600W. You DO need a lot of its a
comnbi system trho, since it has to het the water onthe fly,..but most
of these seem to chop the heating whilst the bath is running anyway...


Roger