DIYbanter - View Single Post

wrote in message . ..
On Thu, 19 Feb 2004 12:52:40 -0800, "John Stumbles"
wrote:

Some systems with thermal stores are arranged rather as the reverse of what
you're suggesting: the thermal store has a heat exchanger from which the
space heating is run. This arrangement tends to be implemented more where
the space heating is true radiators i.e. radiant emitters e.g. underfloor
heating which require lower temperatures of circulating water than so called
'radiators' which are mostly convectors and want higher temperatures. (You
with me so far? :-)

Other conventional ('radiator' based) systems dispense with the always-on
bathroom rad in various ways (which have been discussed at length not to say
ad nauseam in uk.d-i-y, as Mr Google will no doubt tell you if you ask
nicely :-)

I'm not familiar with the systems Mr Stumbles describes, but it sounds
interesting. I may look it up later.

From your initial question it sounds like you are trying to apply the
logic of compressed air systems to heating systems. No doubt you are
aware that when rotary air compressors began to be introduced into
industry the theory was that there would be no need for a central
storage unit. The theory was that the piping in the system would act
as the storage, and since the the compressor would be running
constantly in either loaded or unloaded state, the pressure in the
system would be constant. In practise it didn't really work out that
way.
All the shops I have worked in prefer rotary to reciprocating
compressors, but they all eventually incorporated a central storage
tank such as comes with a reciprocating compressor. It just works
better.

Applying this to heating, I would suggest that even with the water
being circulated constantly through the system with a pump you are not
going to be able to get away from a central storage system.

This is true it seems from the replies, however, since the tax isn't
going to be at any pressure there's a further possibility.

Someone would make a tank that is the shape of the underside of a bath.

This way it would take up useless space, and there'd be no need for
an airing cupboard.

In fact the tank could be any shape.

Every
large system I've ever seen has a circulating pump (or several) in the
system so that the water at the tap is hot as soon as you turn it on.
The problem with that is the inevitable heat loss through the pipes,
even when they are insulated. It just wouldn't be practical or cost
effective trying to keep the water hot with just the pipes to store
it. Just like they told you in 8th grade biology, the nearer a bodys
volume to area ratio is to 1:1, the faster that body loses heat. A
central storage (or multiple storage) system works better for the
purpose, and the bigger the better.

In a situation where you use the radiators in a heating system as
storage this problem would be compounded. I get the impression that is
what Mr Stumbles was driving at. I've only ever worked on the one
floor heating system, but that also had a separate storage tank where
the glycol was heated.

Does that help at all?