On Sun, 25 Jul 2004 22:52:38 +0100, "Set Square"
wrote:

I've done a Google search on "Fuel Guardian" and "Fuel Economy Systems
South" to no avail! Have you looked inside the control box? My guess is that
there are some relays inside, and that it attempts to provide a poor man's
boiler interlock - to turn the boiler off when the demands are satisfied
(although it can't totally achieve that without valves). If a relay had
failed it would probably prevent the heating from working. Worth
investigating, anyway!

I've looked inside, and there are a couple of relays in there. The
trouble is that I can't find a supplier for this unit (I also tried
Google to no avail!)

If all else fails, you could throw away this box and install a conventional
programmer - but this won't use the cylinder stat unless you also install a
motorised valve. If you *do* include a valve, you can have a C-Plan system
with full boiler interlock. [See
http://content.honeywell.com/uk/homes/systems.htm ]

I do have a conventional programmer - it's connected to the Fuel
Guardian box. That's why I can't work out the purpose of this
mysterious box!