Wiring RF Stat to Unica HE 32

[ntl142]

I mean that every connection on M5 was 240v. Power to clock, and the black wires. When I removed the switching leads between M5 and the clock and tested the remaining red and black wire on the underside of M5 (PCB to M5 connection), they were 240v. Perhaps I'm not using the right terminology, but that's what I'm calling the "switching circuit", and it was indeed 240v. Not 24v.

 

[stem]

If you look at the diagram below from your boiler manual.

Counting from the left of the M5 strip of terminals, 1 & 3 are the 24v switching circuit from the boiler. [the loop between them is only fitted if the room stat or timeswitch isn't present]

Terminals 4 & 5 are simply linked to the 230v supply from the mains supply to the boiler, as a convenient way to supply the 230v power to operate the boilers optional integral timeswitch.

See below. 24V for the switching circuit!

I don't know how you manged to get a 240v reading on your multimeter. Unless the manual is wrong.

 

[ntl142]

M5 and M3 are in the 240v section on the RHS. The "optional devices 24v" section is M4 and M3a, the LHS. This is clear in the 2nd photo you just posted.

24v is the blue box in this photo. 240v is the red box. The photo shows the same field of view as the 2ne photo you just posted.

http://tinypic.com/view.php?pic=sw39k2&s=9#.Wdeqg8ZrxKI

 

[stem]

Ah OK then, I thought M5 was in the 24v section. In that case, it could be 230v. There isn't a voltage shown on any of the wiring diagrams in the boiler manual for those connections that I can see, and all the installation variants show it using 'volt free contacts' which is the way that 24v systems are wired (ie they are not connected to the 230v supply)

However, the voltage is not really important in this case, the two boiler switching wires are shown going to a potential free contact, and contacts don't know what voltage they are switching. And of course this was the way that the original timeswitch was connected.

So to answer your question then. If it is 230v you could wire the Siemens up as a 230v, but you would have to know which wire was the 'live' and which was the 'switched live' in the M5 terminals to do this and this information is not provided. Also as the manufacturer recommends wiring it up using the two switching wires and a potential free contact as you have I wouldn't recommend altering it.

Just to revert to an earlier topic. Previously you said:

I've wired in another external source for the receiver so I'll use that - the Siemens manual recommended it. Couldn't see the point, but done it now anyway. Thanks.

I assured you that this would not be the case. Your boiler manual diagrams show the same mains supply used for the boiler and controls. In fact, notice what your boiler manual states about this, and it's even highlighted for you in capitals:

Having watched the video again I noticed why you might have come to the conclusion that you did.

Whilst the text is correct in principle, in that fitting a multi-pole isolator on the cable to the boiler that isolates all of the wires going into it a good idea, the isolator should be supplied from the same fused connection unit that supplies both the boiler (via said isolator) and also supplies the associated controls. (as per your boiler instructions)

The above diagram is therefore wrong in that it shows a switched fused connection unit in the supply to the boiler instead of a multipole isolator, and an unswitched fused connection unit instead of a fused connection unit. Quite worrying if the video was produced by Siemens.