In an earlier contribution to this discussion,
Murdo MacKenzie wrote:

The central heating system in my house (a bungalow with a floored
loft) has been plumbed entirely with 15mm plastic barrier piping.
While I've never had a problem with the pipes, I wonder about the use
of 15mm for the heating loop. The loop comes from the boiler and is
immediately dropped from 22mm to 15mm and this feeds 6 radiators of
varying sizes. There is also a medium sized radiator upstairs, in
the loft, which is fed directly from the boiler. I'm about to get the
boiler moved from the kitchen to an upstairs cupboard, but wondered
if I'd get better performance from the radiators if the loop was
replumbed to be 22mm all the way.

Any thoughts appreciated.

Thanks,

Murdo

A lot depends on how it's plumbed. If you have a *single* 15mm loop, with
*all* the radiators dropping off it, that's not likely to be very good. On
the other hand, if you have a "manifold" at the 22mm end - with an
individual 15mm flow and return pipe for each radiator connected into it,
it's probably ok.

There are rules of thumb (which I've forgotten) about how much heat you can
reasonably carry in a 15mm pipe (is it 6kW?) - based on flow and temperature
drop. I suggest that you find them, and check your system for compliance
with them.

If you *have* got a manifold, you will need to use 22mm pipe to extend the
flow and return pipes to it from the new boiler position.
--
Cheers,
Set Square
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