Date   : Wed, 01 Mar 2006 00:52:29 +0000
From   : jgh@... (Jonathan Graham Harston)
Subject: Re: OT: Central Heating

"Colin" <cwhill@...> wrote:
> That sounds like a broken pump as the hot water is rising ok (as it does)
> but not circulating except by convection.
 
Odd as it's a new pump, replaced about five years ago. The new
pump seems to be stronger than the old one, as when it starts
running water trickles from the expansion pipe into the header
tank for a few minutes.
 
> The hot water stays in the basement when the bedroom is "off" ( nowhere to
> go except up the pipes which don't hold much) but once the valve is open in
 
The pump and boiler are higher than the rads, so the water is
flowing down.
 
> the bedroom, the warm water rises and displaces the cold which drops to the
> bottom of the system leaving the cold water in the basement.
 
Radiators are a resistance network:
 
           /
       +--*  *---/\/\/\/\-----+
       |                      |
       |   /                  |
       +--*  *---/\/\/\/\-----+
 
When the bedroom is "off" and the basement is "on", then the water
flows through the basement. It has no choice. When the other way
round, the water flows through the bedroom - it has no choice. The
problem is when both are one. Each radiator is to high a
"resistor" to get sufficient flow.
 
> Could still be an airlock somewhere though stopping the circulation as heat
> will still conduct through the airlock but the water won't flow.
 
I can hear the water flowing, and feel the heat spreading through
the radiator as it flows.
 
I got some good advice on empty building condensation by posting
on Sheffield Forum, so I'll try them with the rad problem.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
Our chief weapons are 'who', 'ps -aux', 'kill -9', and a fanatical devotion
to 'reboot -q'.