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!