On Sat, 4 Sep 2004 21:53:07 +0100, "IMM" wrote:

It is. Even a modulating boiler cycles when demand is below the minimum kW.
With a heat bank, no cycling.
Hi,

How much heat is lost when a modulating condensing boiler cycles? Not
much I would have thought, as the heat exchanger probably has low
thermal mass and operates at a lower temperature.

Another way of doing it would be to connect the lower half of the heat
bank/thermal store in line with a differential bypass valve and 2 port
valve in parallel.

Then as the system gets up to temperature and the TRVs close, the
thermal store would take the excess heat. When that reaches
temperature and the burner switches off, the 2 port valve would open
to release the heat back into the system.

cheers,
Pete.