"dennis@home" wrote in message
.uk...

"Doctor Drivel" wrote in message
eenews.net...

It operates at a wider temperature differential.

But the temperature differential is determined by the size of the
radiators
and the flow rate and not by the boiler.
I still don't see why there is a difference between the two types.


You can increase the efficiency of a non-condensing boiler. Insert a
blending valve on the boiler return set to 60C (it doesn't go below
dew-point inside the boiler). This is common practice with commercial
boilers using a motorised mixing valve. This mixes system return water
with
flow water from the boiler. Design the system to run at 80C flow and
60C
return, and balance the system to achieve 20C across the heat loads. I
would only do this with a one-piece heat exchanger. You can then
downsize
the pipes. Note: the makers would always say runs at 80C flow and 10C
temp
differential. If you know what you are doing you can greatly improve
efficiencies



Increaseing the temperature difference reduces the efficency of the
radiators.
(The top would be at 80C the bottom 60C assuming no losses in the pipework
(insulation).)

No, not at all. The radiator has to be sized for that room though at 80 -
60C..

Incidently mine runs at 85C flow and 75C return but its sized to maintain
temps down to -15C not -1C like most are.

Don't do this with normal radiators they will burn at that temperature.
(Skirting heating works well at that temperature.)

I think you will find that is the reason they use mixing valves and low
tempreture flows in business.
It is better to have large radiators at 60C than be sued by running them
at
80C+.

Nothing at to do with suing. It is to do with efficiency. Scandinavian
countries have had 60-40C for many years.