Microbore pipe length help

Hi,

I've got a bit of a sticky problem. I've just bought a house and need to install a rad in my lounge. Previous elderly occupant only had a gas fire in there (bizarrely). I've worked out i'll need a rad putting out 3500 BTU. No problem, i've installed rads and pipe before. Trouble is, I have a purely 8mm microbore system, with just one combined manifold. I've got spare feed/returns on the manifold for 8mm pipe. However, the manifold is at the front of the house, and the closest I can get the radiator means a very long run in microbore - 18m in total there and back. It's an open vent system, with a 5m head pump. I can't find a decent set of tables to work this out, and in any case would like to be sure before I try it!

Will I be able to get 3500 BTU out of such a long run in 8mm?. The only other size pipe i have is 22mm to manifold from boiler. I don't really want to do anything with that if I can possibly help it. It's a small system, only 6 other rads, all of less than 3500 BTU output, and within 6m of manifold -i'm pretty sure this new run will be the index.

Thanks in advance!

It must be a very small lounge or very well insulated for such a small rad.
Have you allowed for bends in your pipe length.

I would be inclined to use at least 10mm pipe. It can still be connected to the manifold via a very short length of 8mm if necessary.

If it was my house.... these days I would probably run 15mm from a reducing tee into the 22mm supply pipe near the manifold, to make it a bit more future proof along with a nice big lounge radiator.

Cheers,

It isn't a small lounge as such - it's actually part of an L shaped lounge diner. Working out in two sections, the other half already has a rad slightly oversized, and the 3500 BTU is actually slightly oversized as well. I've found a different way to route pipe - so i'll do it in 10mm and step down at manifold. Managed to get total pipe run down to about 13m, which sounds much better.

Thanks again.

djr1 said:

Cheers,

It isn't a small lounge as such - it's actually part of an L shaped lounge diner. Working out in two sections, the other half already has a rad slightly oversized, and the 3500 BTU is actually slightly oversized as well. I've found a different way to route pipe - so i'll do it in 10mm and step down at manifold. Managed to get total pipe run down to about 13m, which sounds much better.

Thanks again.

Click to expand...

are you sure your measurement shouldn't be 3500 watts, not btu's, the rad i have in my bathroom is bigger than 3500 btu's (3412 btu's = 1kw)