"Phil Addison" wrote in message
...
On Wed, 13 Aug 2003 11:01:15 +0100, "IMM" wrote:


"Phil Addison" wrote in message
...
On Wed, 13 Aug 2003 00:36:41 +0100, "IMM" wrote:

"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.

Why on earth fiddle with different
sized pipes to (attempt to) balance
the rads. Just use one size and balance
with the LSV. calculating what
length of what resistance would be
needed to correctly balance is quite
beyond a c/h fitter, wheras turning a LSV is not.

You are supposed to size up the pipe sizes correctly.

Obviously!! And I did not suggest otherwise.

You did. You said "Why on earth fiddle with different sized pipes".

If you had knowledge of
flow physics

If you knew anything about CH you would keep quiet.

you would know that
the 'correct' size is a bore that is
large enough to pass the required flow rate,
OR BIGGER.

No. The right size is the right size. not bigger or smaller.

Sizing up for each
rad on a manifold system is very easy.
Attempting to do it on a 22/15mm
small bore system is far more complex.

The calculations are identical,

The method is not. In a manifold system, you size uop the pipe from the
boiler to the manifolds. easy enough. Then from the manifold to the rads.
In a small bores it twists and turns with bores and tees.

Those that can't do the calculations,
and it appears that includes you,

snip you are a fool, I go no further


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