On Sat, 12 Jan 2008 13:27:10 +0000, fred wrote:

In article , Sam
writes
On Sat, 12 Jan 2008 11:20:40 GMT, fred wrote:

In brief, on the subject reducing pipe sizes, thing of the pipework as
the a tree with a main trunk and smaller branches coming off the main,
once the trunk is split there's no need to have a full size branch all
the way to the top just to support a few leaves at the end.

Thanks. I could understand that but the reduction is size occurs before
the branches. The 28mm goes from the boiler to the airing cupboard but
before it gets to the cylinder changes to 22mm; there are no branches on
that it runs to the cylinder only. The CH goes from the boiler in 22mm
to the landing and splits into 15mm before that branches. My other worry
is that once it's branches, posts here said 15mm supports only 6kW.
Surely one big rad could use all that up?

Do you mean a single 22 reduces to a single 15, I ask as you say splits
into 15mm which suggests 22 splitting into 2 (or more) 15mm.

28mm dropping to 22mm for a short length is ok as (say) 8m of 28mm plus
2m of 22mm has less resistance to flow that 10m of 22mm.

The reduction to 15mm before the branches doesn't sound right but it may
still be a serviceable design, try the balance and if that doesn't sort
the problem then an upgrade to 22mm may be in order for a further part
of the run.

Gravity fed H/W is not my forte but the heating comments should still be
valid, I assume there is a separate pump and zone valve for the heating
circuit.

No one's mentioned, yet, what the temperature from the boiler is.
There are such lot of basic simple stuff before we get into the subtle
stuff.
1) Is the primary flow form the boiler touchable?
2) Are all the radiators hot?
3) Are all the radiators hot all over?


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html