"Pete C" wrote in message
...
On Thu, 2 Sep 2004 19:18:52 +0100, "IMM" wrote:

"Pete C" wrote in message
.. .
On Thu, 2 Sep 2004 15:05:07 +0100, "Christian McArdle"
wrote:

Hi,

Just a general point, I wonder if it would be better to run the
radiator return through the heatbank lower coil, with a pipestat and
bypass valve across it.

Then as the return temperature from the radiator rises, the valve
would open so excess heat is dumped into the heat bank, reducing the
flow temperature to the boiler to promote efficiency.

If there was a sudden demand on the radiators, the lower temperature
would close the valve so the boiler sees a lower return temperature.

Otherwise the return temperature to the boiler would slowly rise until
the boiler cuts out but the heat stored in the lower part of the heat
bank would help keep the radiators hot and delay the time until the
boiler fires again.

There's probably some more potential in this idea if I could think of
it

The rads directly off the heat bank. The return of the rads runs through
a
plate heat exchanger and then back to the heat bank. The return from the
heat bank back to the boiler runs through the plate heat exchanger. The
returning rad water would cool the returning boiler water lower the
temperature. They may be case where this may not occur, but these
occurrences would be few and far between.

Hi,

I might be getting mixed up with a
thermal store. The rads would be
connected directly to the boiler
and return through the lower coil of
the cylinder. Basically the lower half
of the cylinder would act as a
buffer to reduce cycling when central
heating demand is low.

So a normal direct rads from boiler and a quick recovery cylinder with an
extra coil at the bottom?

I could improve matters. You are using the bottom half of a cylinder as a
hot water store to prevent boiler cycling. May as well sue a proper heat
bank/thermal store. It will lower the rads return temperature going back to
the boiler, but how much is well ..err...not known. My gut feeling is not
by much. Then you have a stat and a 2-port valve as well and the extra
expense of the coil in the bottom of the cylinder. A plate heat exchanger
is passive and will drop the return temperature quite sharply