Unknown Cable

I get the impression from what you're saying that you haven't found either end of this cable.

That is not going to help you know what voltage(s) it carries, nor to test it for dead, nor to know what will happen when you cut it.
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The only hope I have is that is terminates in the airing cupboard in either the boiler or the telephone. The other end disappears into the wall somewhere. This was only discovered when I took the ceiling down. As far as accessibility goes, I can make it accessible through a box or something in the plasterboard.
Not best practise, but needs must….

If teh wire is only 5mm, whay not notch put the underside of the joist?, remembering where it is so you don't screw it woith a plasterboard fixing.
Here are some pics, should be able to work out the size from the 20p piece alongside.
I have traced it back and it goes into a power switch near the boiler (i guess this is on and off) There is thick twin core and earth (I assume) going into this power switch also so i think that it is the cable that goes to the thermostat which is downstairs in the kitchen. The cable in question is the cable on the far right of the power switch

If this is the case then what cores are likely to be inside this cable and how can i cut and reconnect, i have crimps and also WAGO connectors and i can put this is somewhere that i can get to if need be (obviously i will be turning power off etc).


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Does it definitely go into that switch, rather than just passing behind it?

Maybe have a look inside the switch (after turning the power off) - that will show you what conductors there are.

It looks rather thin for a mains cable to me, but I suppose it's not impossible.
I have traced it back and it goes into a power switch near the boiler (i guess this is on and off)
Don't you know?

Do you also not know that people can die from trying to do electrical work on the basis of guesses?

Stop guessing and find out the facts.

There is thick twin core and earth (I assume) going into this power switch also so i think that it is the cable that goes to the thermostat which is downstairs in the kitchen.
Stop guessing and "thinking" and find out the facts.

If this is the case then what cores are likely to be inside this cable
The number you can see at the ends where the outer sheath is removed. Don't ask people here to guess what you have - find the ends and establish the facts.

and how can i cut and reconnect
Depends on what you find the cable is, what voltage it carries, etc.

(obviously i will be turning power off etc).
If you don't find the ends of the cable how will you test that it is dead?
is round or flat, we have gathered its floppy. Is it white, cream, brown or black? Could be a bit of TV coax. Its a bodge, but just put a pin hole through the plaster boards where you are letting the cable to cross the joist and either notch the underside of the joist or groove out the plasterboard. The pin hole is so you can avoid it when fitting the plasterboard with screws. Or put reference marks on the walls.
OK finally got to the bottom of this one thanks to you guys. It appears that this is a telephone cable. I still have to do a bit more investigation but it appears that this cable goes through the back of the power switch (as someone suggested) and ends up in the back of the telephone extension socket. My next step is to either bite the bullet and cut it and see if I still have phone line as it is an old house and I have an overhead cable going into the house but I am sure that this runs down the outside of the house into the master socket which is in the hall. This cable appears to run towards the back of the house which I can only assume used to go to an extension socket somewhere at the back of the house which is not there anymore. My home telephone is connected to the master socket (not sure how) and then its wireless all the way so if it is for an extension it is not needed.
Anyway, bit more work to do on tracing it, I think that I will probably cut it and see what happens as this is going to have to happen anyway at some point.
Many thanks for all the help I have had from here, really appreciate it.
Don't just chop it through!

If it is connected, you could do some damage.

If it is running through an electrical accessory pattress, then that is wrong.

Carefully cut enough of the outer sheath away so you can cut the inner conductors separately.

Isolate the power and then remove the cable from the pattress.

Then terminate the cable in a telecoms JB:


and hold the cable in place with a couple of clips.

This way, it is safely terminated and you can use or extend it in the future if necessary.
I will get hold of a telecoms junction box and tool as suggested, as far as i can see, this isn't going through any power at all, this one is actually just running behind the patress (not connected to it), what are telephone cables powered by? Want to make sure that if i turn the power off this will turn the power off to this cable
Phone wires are powered from the exchange. Turning off your electricity will not affect them.

The voltage is high enough to give you a surprise, but not enough to cause an injury (unless maybe you're on a wobbly ladder).

If you have reasonably modern phone wiring, you can open up your "master socket" to disconnect all the secondary wiring from the exchange. If you don't have that sort of master socket you may choose to "work live"; I probably would. Slice into it with a knife and remove an inch of the outer insulation, then spread out the individual wires and cut them individually so that they don't touch. Then strip the ends and join them in some sort of junction box.

Have you traced how this connects to your other phone wiring? if your internet box is beyond this point you should be more careful about doing a neat job as it may affect the signal quality.
I would be very suspicious of any wire passing through a pattress, though. You never know if some half-wit might have decided to use a spare bit of telephone cable to carry mains voltage. Stranger things have happened. Turn off the power and have a good look inside. You really ought to find out where it comes from and where it goes to. Telephone cables are twisted in pairs to resist picking up interference when they pass close to other cables, but it would be infinitely preferable to separate them by a foot or so. Possibly removing it and running a new piece in a better position.
This one doesn't go into the pattress, just runs behind it in the corner of the cupboard. I can certainly see where it comes from but I have no idea as to where it goes, there are only 3 extension in the house (this one, the master socket in hall and in living room) and this cable goes nowhere near those although that.

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