On 29/12/2009 20:59, Andrew Gabriel wrote:
In article1PKdnY6J7NWZ06fWnZ2dnUVZ8qudnZ2d@brightvie w.co.uk,
Tim writes:
Wondering why the living room rad was not getting hot, I remembered I'd
turned off the one in the conservatory - common wall. Looking at that, I
discover these two rads are in series, but there is the possibility to
turn a screw in a pipe a 1/4-turn, opening a valve, and thereby short
circuit the hot-water *around* the conservatory rad. This rad is still
off and the living room one is now nice and toasty.

That's a little bit like a single pipe circuit, except you wouldn't
have any means to close off the "short-circuit" as you call it.
It's not a short circuit actually - the radiator presents less
flow resistance than that pipe, aided even further by the convection
current if the radiator is losing heat to the room.

Even, you mean, when the pipework to/from the rad has some right-angles,
whereas my "short-circuit" is a straight pipe with the isolator valve in
it? Interesting. (I take the point about the convection/cooling).

I wonder if the valve was added by someone who didn't understand a
single pipe circuit?

Certainly whoever installed a lot of this stuff did a gash job. I've got
a rad half-hanging off a wall, a towel-rail rad on another wall at an
angle because the installer should have cut another 1/2" off the pipe
going into the wall, 1/2" pipes going into 1.5" holes ...

I'm gonna have to get a man in - but not til the weather is warmer.

--
Tim

"That excessive bail ought not to be required, nor excessive fines
imposed, nor cruel and unusual punishments inflicted"

Bill of Rights 1689