"Andy Hall" wrote in message
...
On Sun, 26 Oct 2003 12:01:28 -0000, "mike.james"
wrote:

The point is that the boiler heat exchanger is rated to give 20
degrees temperature lift at full burner output - that's it. At
lower outputs it may operate with lower temperature differentials.

Right - now I've got it.
Many thanks.

I'm focusing on the return temperature thinking that the boiler can take
care of the flow temperature and bring it up to the higher level needed by
the smaller rads.
You're saying that I have to have a higher return temp to ensure that the
smaller rads are kept as hot as they need to me. So if I do drop the return
temp I'm effectively opting for the lower flow temp.

I need to think about this.
(and read the technical stuff on the Keston)

mikej