I thought it was abandoned ...

[slowlybutsurely]

This house has had 2 new combo boilers since these room/zone thermostats were used (so I thought).

[see pics attached]

When I ripped it out and cut the wire when decorating - and then tested them with my multimeter, I found 2v or 3v between various of the 4 wires in that cable.
What and where might this be coming from please?

(where do I look?)

Thanks in advance.

 

[Mikefromlondon]

Having measured voltages between different wires, therefore for added safety, you should also check all wires against a solid known good earthing point or a conductor, for example what if all the wire tails were live then you have no potential difference, or what if one live wire may show slightly lower voltage due to heavier load on it, so again you may only see 2 to 3 volts against each other, but all may be at potentially lethal 230v against an earth. So for safety always measure them against a neutral potential, an earth acts as a neutral for measuring purpose.

On most wires you can get some residual voltage, these are induced voltage and can be induced into dead wiring running parallel to live wires close by, or induced in the dead wiring from any other adjacent live conductors nearby, and other electromagnetic fields, which are always presence in a house due to some electromagnetic radiation from the house ac wiring and should be nothing to worry about, and as a further safety you could bunch all wires together and connected to earth so that should any become live then earth will take care of any deadly currents and blow out a fuse or trip the RCD.