Hi all

I am trying to improve the operation of my central heating system and would
appreciate the opinions of the more experienced group members.

The story is:

Originally 3 bed detached 1970s house.

Additions since built:

1 Kitchen extension with 1 rad single panel rad 1200 x 600
1 Back room extension with 1 double panel rad 1000 x 600
1 Bedroom/En suite with rad and towel rail (see link)

http://www.thesculls.freeuk.com/Radpipes.jpg

Referring to image (which shows upstairs piping and radiators only), the
problem is little heat to new bedroom rad 7 and almost nothing to towel rail
6.
Downstairs main runs are 22mm, but upstairs is all 15mm.
Not sure if it is significant, but the new part that hardly works is piped
in plastic - see link for plastic/copper joint location.

Another factor that may affect the towel rail operation is the height.
Somewhere I seem to remember reading that a certain distance was required
between the top of a towel rail and the underside of the loft CH header
tank. In my case this distance is approx 650mm.

I have tried major throttling of the downstairs rads to improve flow
upstairs, but do not seem to be able to get acceptable performance of
upstairs and downstairs rads to include items 6 and 7.

So the question:

Looking at the pipe runs and radiator sizes involved upstairs, are 15mm
mains simply not up to the job?

Thanks to anyone who has even managed to read this far!

Phil