"Andy Hall" wrote in message
...
On Sun, 9 May 2004 20:45:09 +0100, "Vortex"
wrote:

Hi,

Shortly I want to upgrade my gas central heating from "vented" to
"sealed"
(primary reason to eliminate the loft tank to make way for a future loft
conversion.....secondary benefit is that I'll be able to put a rad up
there.)

Both good reasons, and there are several more if you look in Ed
Sirett's FAQ on it.

Yup I've read it. Very useful


You can certainly go larger, and there is no reason not to do so. I
have a boiler with a 10 litre vessel built in, but on calculating the
size, it might have been marginal, so I added another one also of 10
litres.

18 litres it is then. £2.85 more than an 8 litre vessel!!


While I'm at it I want to put in "bleed valve" on a spur off the main
boiler
flow (actually this is where the fill and vent pipes will be removed) for
easy introduction of Fernox. Is this normal practice? Seems to make a
lot
of sense to me.

Yes you can do that, although you may prefer to put it at a higher
point. If you are adding a normal system dose of MB-1 it's 4 litres
and depending on layout and drain arrangements, you might not have
enough capacity below this point.

You will also need vents at high points anyway to let air out. These
can be manual or automatic.

Actually I was thinking of the Fernox Gel so the capacity is a non issue
really.

Now I have a new query. I've just been reading the boiler manual (Potterton
Prima F, 10 years old), and for a sealed system the diagram says the Safety
Valve, pressure gauge and axpansion vessel should be connected on the flow
side of the boiler but before the pump (makes sense). It shows the filling
point as being on the "return" side of the boiler. Why? I can see no good
reason.

David