On Wed, 3 Dec 2003 10:20:32 +0000 (UTC), "Colin M" wrote:

Yes, one is all that is needed.

With the IR device I could tell within a few seconds that the boiler had
switched off as the inlet temp dropped by a couple of degrees between
measurements. I doubt you could see that with the mechanical devices and
their inertia.

Colin

Great thanks guys that's one for my Christmas Present list :-)

Sad but true...