On Sun, 17 Dec 2006 19:15:29 +0000 (UTC), Ed Sirett
wrote:

On Fri, 15 Dec 2006 22:11:11 +0000, Stuart wrote:

Four of my 7 rads are done in 8mm microbore from a manifold in my hall and the
other 3 rads are fed by 10mm tee'd in to the 22mm before the manifold . As I am
getting a replacement condensing combi boiler and the fitter said 10mm was
preferable to 8 I wondered if cutting the 8mm just after it leaves the manifold
and then replacing it with 10mm would work better or would the couple or three
inches of 8mm still create problems ( if at all) . I had thought all were done
in 10mm and it was only after he left ( thinking they were all 10mm as I was)
that I had a closer look and noticed the difference so lifted a couple of boards
over the manifold and checked what was what .

I don't know why it was done that way ...can you not get 10mm manifolds ?


Looking at the other posts it would appear that you have been introduced
to a range of replies.

Provided:
1) The existing system, when it worked, worked well enough to heat all
the radiators enough to heat the house properly.
&
2) There is absolutely no hint of sludge or scale in the existing circuit

then keeping the existing 8mm and 10mm pipes will be a good choice.

Obviously 8mm pipework is even more prone blockage than larger sizes but
isn't automatically a problem.

The existing system worked on the basis that the difference between the
flow and return temperatures would be somewhat more than a system using
larger pipes. This is all to the good when using a condensing boiler.


Thx Ed ...I'll get the new boiler fitted and see how it goes ..

Stuart .