In an earlier contribution to this discussion,
geoff wrote:

In message , Roger Mills
writes
In an earlier contribution to this discussion,
geoff wrote:

In message , Roger Mills
writes
In an earlier contribution to this discussion,
Dave Osborne wrote:


Well, I'd be willing to bet that there are many millions of
systems out there wired to a classic Sundial plan. Mine is, for
one... :-) However, I'm quite happy to do additional drawings for more
modern
installation arrangements.


From my limited reading, the following ideas come to mind:-

1. Wiring diagram for S-plus with one and two extra heating zones.

Yes - good idea.


2. Conventional (i.e. not system) boiler with pump-overrun timer
(as you have suggested above).

Yes - although it's not necessarily a *timer* per se. My boiler
simply keeps the pump running until the output temperature falls
below the boiler stat setting.

What boiler is that ?

It's a Mk I Baxi Solo powered flue jobby - c1990 vintage.

Ah - simply switched from the stat then, the solo2 the pump overrun
would be time, not temp controlled

Yes, that's right. There's an extra set of change-over contacts on the
boiler stat which connects the pump either to boiler demand or to permanent
live depending on whether the boiler is below or above the set temperature.

Unfortunately, this doesn't always have the desired effect! There are some
cases where the demand is cut when the stat is just below the set point, so
the pump is immediately cut. The residual heat then sends the temperature
up, and the stat switches so that the pump comes on again - but too late to
prevent the over-heat stat from tripping. So I have re-engineered mine by
using an external timer (intended for bathroom fans) which keeps the pump
running for about 4 minutes after the boiler has switched it off - thus
avoiding the above problem.
--
Cheers,
Roger
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