On Sat, 09 May 2009 21:08:26 +0100, Tim S wrote:

Heatmiser, but all their stuff is programmer/thermostats and intend the
unit to be in the zone, with remote control possible via RS485.

How about a time delay relay and push switch just bridging the output
contacts of the programmer (aka flats hall lighting delay relay)?

That would be my favorite solution. I looked at something similar for one
of the local community halls to provide a simple "Press for heat" button.
Plenty of options of off the shelf DIN rail devices with suitable delays
and non-retriggerable ones as well. ie once triggered it ran for it's time
period then off and could not be retriggered by pressing the button again
turing it's run time or for a given period after.

Another solution is hacking into the programmer and extending wire from
across the boost switch in the device. Might have problems with long wires
and interference causing false triggering mind.

Or can't you put the programmer in the zone seeing as you're going to
run wires there anyway?

Two wires for a button (three if you want feedback that the button push
has been registered) or the whole bundle for the power, button and
switched output back to the central point...

--
Cheers
Dave.