View Single Post
  #4   Report Post  
Posted to uk.d-i-y
Dave Liquorice[_2_] Dave Liquorice[_2_] is offline
external usenet poster
 
Posts: 14,085
Default Back boiler: friend or foe?

On Mon, 4 Oct 2010 22:12:08 +0100, Phil L wrote:

Heat has a tendency to rise, so it's unlikely that hot water will 'fall'
down the pipes into the cold back boiler


Heat moves from hot places to colder places in any direction.

Hot objects expand, thus they become less dense than colder parts of
the same object. If the object can flow like in a fluid or a gas the
hotter, (less dense) will be pushed up an away by coldler (denser)
flowing in underneath.

So the hot water in the cylinder above the colder water in the back
bolier is going to stay up in the cylinder. Well the heated water in
the primary coil rather than the cylinder contents. It might be worth
checking how the gas boiler is plumbed into this system. It might be
that the flow (gravity or pumped) through the gas boiler also
introduces an unwanted and wasteful flow through the back boiler.

--
Cheers
Dave.