"BAHADIR" wrote in message
om...
Hi everyone,
i have a final project about single pipe central heating systems, and
heating a building with the system...
i am studying mech. eng. and i need detailed information about this
subject...
it would be glad if there are anyone can help me...
it may be your own knowledge or experience about the system or may be
a link to a site about system...
Thanks For everyone who will answer me.....

With a one pipe system the pump speed can't be too fast otherwise the water
just bypasses the radiators and leaves them cold. They are used in large
commercial systems where the loop pipe is oversized, so the loop is no too
cool at the end. The are used in large system as running two 1.5" pipe in
parallel is not practical and visually looks appalling. The designer will
size the loop pipe and the radiators along the loop; the end rads will
probably be much larger than those at the beginning of the loop.

They were used in domestic systems in the 1950/60s to keep costs down when
copper pipe was more expensive. Some would have a two pipe system on the
ground floor and a one pipe on the first, where temp were lower and in those
days the bedrooms were deemed to only have only background heat. When
someone changed a pump and left it on the highest speed, the bedrooms went
cold. I have seen a one pipe system ripped out to great expense because the
pump was set too high, the "plumbers", not heating engineers, didn't know
what was happening.

A one pipe system with a condensing boiler is a no, no, as it keeps the
return temp far too hot. A condenser needs the return pipe temp as low as
possible. One pipe systems are difficult to balance the rads.

In short a one pipe system is the worst case. A two pipe flow/return system
is the best, as then you have far more control and balancing is far easier.
An extra copper pipe is not expensive in a domestic system.