In reply to gethin_allen:
> Looking at the diagrams in the Siemens manual it appears that be used to supply a current to a boiler or pump, you don't want this, you just want what is effectively a fancy switch that when the room thermostat/controller wants to turn the heating on/off is closed or opened.
> Only do this if you understand what I'm blabbering on about and be very careful with any live connections.
> Connections Lx and L1 on the base unit are shown as being switched and according to the thermostat spec sheet will switch anything from 24-250v.
> To test this, If you wire up terminals L and N to the 230v fused supply and then with the thermostat in the OFF (no heating demand position) test both the continuity and voltage across the Lx and L1 termini, this should show no voltage and an open circuit.
> If you then switch the slider to constant heating demand (slider 16 in the diagram) or press the override button on the base station this should result in a closed circuit between termini Lx and L1 but no voltage.
> If this is the case, check your mechanical clock you removed that when in the off position the circuit between the black termini is open and in the on position the circuit is closed.
> If all is as stated I'd connect the Lx and L1 termini of the thermostat to M5 A and C on the boiler, Lx to whichever of A or C is live and L1 to the one that is return/neutral.
> Saying that I'd do this does not mean that you should if you don't understand my logic for suggesting this. Obviously I can't take any responsibility if you mess things up.
This all makes sense and is similar to what I had thought too - thanks. I want to verify if 0, 24 or 240v is going through the black clock wires when it switches. If 0 or 24 then I do the normal wiring for a simple switch (at 3.26 for 24v wiring in the video). If 240v then I wire as per 3.39 (240v wiring) in the video.
The video shows something that's not included in the wiring manual for the thermostat, so it's adding a layer of confusion.
3.26 (24v wiring) or 3.39 (240v wiring).