On Wed, 28 Sep 2005 13:43:02 +0100, Mr Fizzion wrote:

Can you have such a thing or is this one of Doctor Evil's fantasies?

If you can...how would you do it?


For me this is just plain nonsense.

1) I doubt very much whether any manufacture would permit the boiler to be
used in this way.
2) The boiler is not designed to take luke warm let alone hot water as
it's input.
3) All the while the 2ndry pump is going the boiler is in DHW mode. When
does the house get heated?
4) The whole system would rely on the boiler shutting down because the
primary is at or over its maximum temperature for DHW mode. This will only
happen when the DHW temperature is very hot. Ergo the heat losses on the
2ndry loop will be huge.
5) Whilst the burner is shutdown the fan will still be going so that the
primary will be losing heat at a rate comparable with the burner rating
i.e. tens of kW. This is going straight out the flue!
6) The water bylaws
forbid the permanent connection of the mains to a closed circuit.

If a house needs a secondary loop it also needs a grown up heating system
that will include a stored HW of some type (vented, unvented or thermal
store).

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html