On Tue, 26 Oct 2004 21:18:40 +0100, Simon Hawthorne
wrote:

Hello again

Wonder if I dare ask another basic question?

Of course :-)


I have 8mm microbore feeding all my rads and I really want to change
them for some new ones (the old ones are looking rough - with the odd
rust patch appearing now). I also want to fit TRVs - and until now,
didn't realise you could get them in 8mm...! The 'Honeywell VT117E
8mm' is available from a few sites, and Plumbworld (when the website
worked a few minutes ago) did a pack with a lockshield valve.

Am I correct in thinking that a nice new rad (I'll do all the kw
calcualtions to make sure I get one that matches), a 8mm TRV and 8mm
lockshield valve, a pack of 8mm couplings (with the solder built in),
a blowtorch and some patience, I could actually pull this off and fit
a new rad?

You could indeed.

A few suggestions.

- Get a small, good quality miniature pipe cutter - don't use a
hacksaw. Plumber's merchants sell them quite inexpensively, normally
made by Rothenberger. Make sure you get one that will cut down to
8mm, some of the large ones won't or mangle the tube.

- Get a small hand held pipebender for microbore tubes. You can get
a cheap one for about about £15 e.g. Screwfix 17898

You may need some 8mm copper tube as well. It's better to get some
that is fairly new because it is then softer to work with - it hardens
as it ages.

Don't forget to get a heat mat to put behind the work when you are
using the torch.


I'm assuming these 8mm couplings (with the solder rings) are 'dead
easy' to use - so long as the pipe is clean.....(any one got any links
to some good websites that can talk me through it - I've read a few
books but am a complete amateur!).

They are. Essentially it's a case of thorough cleaning, smear on some
flux and heat with blow torch, applying solder when the piece is hot
enough. One thing with small tubes like this is not to overdo the
solder. It can run inside the fitting and partially or completely
block the pipe. You only need a small touch - none if you use solder
ring fittings.



Finally, http://www.plumbworld.co.uk/1358-12702 - is a TRV pack that
says it is for 8mm/10mm pipes - how does that work then? How can it
fit both...

It probably comes with alternate compression olives or a reducing
ring.

How long are the pipe runs going to be? For up to a few metres (say
less than 10 total flow and return then you can run a radiator of up
to about 1500W rule of thumb. If it's longer then you will need
larger pipe - e.g. 10mm will do 2500W.




..andy

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