In article ,
Hugo Nebula abuse@localhost wrote:
_____ _____
-|_____|-|_____|--¬
| |_ 3 N (Blue)
|_______________
\|____ 2 H (Yellow)
.
|______ 1 TL (Red)

The new thermostat has connections for Common, Heating Satisfied and
Call For Heat. Which is which? Am I right in thinking H (yellow) is
Call for heat, TL (red) is Common, leaving N (Blue) as Heating
Satisfied?

If it's any help, I've traced the wiring back to the main wiring
block, and the red of the existing thermostat connects to the live
from the programmer, the yellow connects to the white of the 3-way
valve, and the blue to blue wires from the pump, 3-way valve and
boiler.

The blue is likely neutral and not needed on a battery operated stat.
Insulate and tape up out of the way. (It was needed for a heating coil in
the old stat to improve the accuracy and response of a bi-metallic strip;
modern units use a solid state sensor which is vastly more accurate and
reacts near instantly.)

To simply replace the existing one, red to com and yellow to call for
heat. The heating satisified - the normally closed contact - would be for
'special use'. To use it would likely need a total re-jig of your wiring
and IMHO isn't needed to replace a 'standard' thermostat.

--
*The colder the X-ray table, the more of your body is required on it *

Dave Plowman London SW
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