In an earlier contribution to this discussion,
Stephen wrote:

On Fri, 5 Sep 2008 22:53:45 +0100, "Roger Mills"
wrote:

A radiator's output at dT=40 is only 60% of the output at
dT=60.

Thanks, so I actually need a larger radiator that it first appears
from their catalogues. For example if I needed a 4.7kW rad, I ought to
be looking for a 4.7/0.6=7.8kW rad according to their stats. How
confusing!

If the output is quoted at dT=60 and you're going to run it at a dT of 40,
then yes - that's right.

However, many manufacturers are now quoting the output at dT=50. The output
at dT=40 is about 76% of that at dT=50. So, if you're looking at a catalogue
based on dT=50, you'll need 4.7/0.76 = 6.2kW for the example which you
quote.

Hopefully you won't *actually* need an output of 4.7kW, unless you've got a
very large room with very poor insulation and draft proofing! [I've got a
large L-shaped lounge with quite a lot of glass, and my calculated heat loss
for that is less than 3kW]
--
Cheers,
Roger
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