"Phil Addison" wrote in message
...
On Tue, 12 Aug 2003 23:51:40 +0100, "IMM" wrote:

Just to add:

Plumbing Mechanical Service Book 2,
a NVQ plumbing book. This is not a DIY
book so please don't buy. It has a section
on heating, and a sub section on
Mini-bore on page 170. It says:

"If the manifolds can be situated in such
a way that the branch flow and
return to each radiator is approximately
the same length, the frictional
resistance will also be approx the same,
making the system self balancing".

That is plain wrong.

It is plain right!

Making all the pipes the same length will indeed
make the each rad feed have the same resistance. But that is NOT what is
required. Different sized rads require different flow rates otherwise
the small rads will steal flow that is needed by the large ones.
Balancing is the process that adds the extra resistance to the small
rads to achieve this.

Each rad will not have the same pipe sizes. A small rad may only have 8mm
and a larger rad 12mm. The pipe sizes will create resistance in themselves.
Manufacturers did not make lockshieldless valves for nothing.

Sigh....

Yes sigh



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