Re: [CAD_CAM_EDM_DRO] Re: OT: Intro + Q:Selecting workshop heater

----- Original Message -----
From: "Tony Jeffree" <tony@...>

> In practice, the flow through each circuit will be affected by the length
> of pipe run in each flow/return - twice the length of pipe will give twice
> the resistance to flow; similarly, if you mix the 6, 8 and 10mm diameters
> in the same installation - this is straight "Ohms Law" stuff. But it is
> easier to balance flows than with a small bore or large bore installation.
>

You are partially right here but, if the system is designed right, the pipe
sizing should be directly related to the size and output of the radiator and
the run length - it can be an awkward calculation but, fortunately, tables
are available to help. If the sizing is correct, all the rads should heat up
equally.

>
> Hmmm. Nice theory, but I can show you an installation here in my house
> (NOT installed by me) that can and does create horrendous airlocks if you
> don't re-fill the system carefully after draining it down. Had a plumber
> in to do some mods on one occasion - it took him the whole of a morning to
> bleed out all the airlocks.
>

I'm afraid this sounds like a fundamental design problem - do you have air
venting valves on each of the manifolds? If so, and the primary pipe runs to
the manifolds are rising all the way to the manifold, there should be no
problem at all. I suspect that the primary pipes go downhill a bit before
reaching the manifolds (not the initial vertical drop from the boiler but a
'hump' in the horizontal part). This would create an airlock in the
large-bore pipe which could be very awkward to get rid of. If you could
identify such a 'hump' it is possible to drill a hole in the highest point
and install a vent valve there (an automatic type would be best) which would
get over the problem. I've never known an airlock in the microbore part and
some of the ones I have installed snake all over the place - one even went
up and over a doorway hidden behind the door casing and skirting boards
where an extra radiator was wanted in a solid floored extension and the only
alternative would have been to dig up recently laid floor tiles (the heating
was an oversight on the part of the architect!)

Ian
--
Ian W. Wright
Sheffield UK
www.iw63.freeserve.co.uk