In article m,
sarmavsn wrote:
I had a Honeywell room thermostat which controlled the Alpha Combi
boiler in the loft. I tried to replace it with a Drayton Digistat 3.

IIRC, these are available in both battery and mains versions. Which one
have you?

It did not work. Can any one please expalin what is the meaning of the
terms, call for heat, satisfied etc?

If you imagine a switch with an input but two outputs one of which is
live and the other dead when the switch is 'off' and reverses when it is
'on'.
That's what most thermostats have with the 'switch' operated by the
thermostat.

With the thermostat set to higher than ambient temperature one output
becomes live and this is the call for heat sometimes marked 'on'. When the
room temperature exceeds that of the thermostat the switch changes over
and the call for heat becomes dead while the other (satisfied) output (can
be marked off) becomes live.

What do thes wires do in real
terms? When I put an ohm meter across the three terminals of the
digistat, nothing happens as the programme calls for heat. Does this
work by connecting terminal 1 to 3 or does it send a voltage signal? Can
some please explain how the system works?

The top terminal is the common so has the live feed. Next down is the on,
and the third off.

--
*If you can't see my mirrors, I'm doing my hair*

Dave Plowman London SW
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