"Roger Mills" wrote in message
...


The simplest way of controlling the hot water - short of converting to a
fully pumped system - is to put a zone valve in the gravity circuit.
Control
this with a cylinder stat, and use the voltage-free change-over contacts
on
the zone valve to contol the boiler. If you have a look at the C-plan
details in
http://content.honeywell.com/uk/homes/systems.htm you'll get the idea.

Perhaps it's not the correct thing to do, but on my gravity (convection!)
system, I use the 'stat on the boiler to keep the water temperature under
control when the heating isn't on. I normally set it to 'minimum' for the
summer months and raise it a notch or two when I start using the heating
regularly. Seems to work.