"Pete C" wrote in message
...
On Mon, 20 Sep 2004 17:29:36 +0100, "Ed Sirett"
wrote:

- Because the cylinder will be in the garage I want a recirculating
pump on
the DHW but how can this work when the water is just being recirculated
around pipework and not through a heat source?

From the furthest HW tap (that you want enhanced) or HW
usage point take a small (10mm hep? 8mm microbore?) pipe back to near the
heat bank. Insulate every piece of DHW to very best standard you can
manage,
including the return pipe.
Obtain a BRONZE circulating pump (this is like the CH pump but made of
bronze and 5x cost). Put small DHW pipe into the pump inlet. The pump
outlet into the mains cold water inlet. Put pump on very lowest setting,
also only open one of the pump isolating valves a tiny bit. You want a
trickle of water to flow out of the DHW supply form the heat bank but
enough to make the DHW pipe warm/hot but not so much that the returned
DHW
is actually warm.
Some poeple say you should put a non return valve in the return circuit,
I think that length of small pipe work and the restriction on the pump
isolating valve should be enough to stop much mains cold being drawn back
and mixed with the HW.
Consider putting pump on timer or PIR so that it only operates at peak
times.

Hi,

Or, use a pipe stat as well to run the pump so it only circulates DHW
when the pipe has cooled down.

This will help to keep the DHW in the heat bank stratified,

No DHW in the heat bank, only primary water.

and has
the advantage that it is more responsive to timer or PIR control.

Another option is to save on an expensive pump is to put a microbore
pipe alongside the heavily lagged DHW pipe or even inside an oversized
DHW pipe.

This would have it's own pump and pipe stat and be connected across
the DHW coil of the heatbank.

Heat has a plate heat exchanger, no coil.

When the DHW pipe cools the pump would
circulate water through the DHW _coil_ of the heatbank, so using a
small amound of DHW heat (but not the DHW water itself) to keep the
DHW pipe hot

cheers,
Pete.