How much insulation to strip off?

[James_H]

In a situation with two 2.5mm T&E cables entering a 25mm back box for a ring socket:
How much grey sheath should be visible beyond the grommet (although depends on which entry hole is used)?
What length of exposed red and black (or brown & blue) insulation should there be?
Do you fold half the bare wire back to double the amount in the terminals?

I've searched for the lengths but can't find anything. My thoughts are that there should be enough for the socket to be removed a reasonable distance from the wall but not too much that the back box is crammed full or the cables have too tight radii when the socket is screwed to the wall.

Thanks,

James

 

[andy]

take it back to where it enters. gives you the most flexability to work with it. normally, i cut the cable enough to go to any position so the socket can easily be changed. if there is only 1 cable going in then you should double the ends to give a better surface area, otherwise leave it

 

[securespark]

This much.

 

[ebee]

take it back to where it enters. gives you the most flexability to work with it. normally, i cut the cable enough to go to any position so the socket can easily be changed. if there is only 1 cable going in then you should double the ends to give a better surface area, otherwise leave it

I disagree.
Most sockets etc will allow 2 x 2.5 doubled over and often a third (spur) . Sometimes the spur is just a single . In that way you approach the ideal ie to fill the hole with conductor to make the best surface contact.
Never twist `em (except perhaps earths) and leave plenty of length to manouvre/cut back damaged bits and fold neatly (avoiding screws) into box.

 

[Steve]

Never twist `em (except perhaps earths)

why not? I would think twisting ensures that if one core breaks loose of the screw's grip, the twisting holds it in place . . .

 

[ebee]

Twisting puts undue stress on conductor (makesit more likely to snap and makes it difficult to seperate for I & T. Doubling is better

 

[Qedelec]

And don't put both earth's in the same sleeving, it is false economy. I have come across several instances where this was done at the CU only to find they were not both on the same ring. Separates make it easier to see where they come from.

 

[James_H]

This much.

I suppose this was a partly a 'how long is a piece of cable' question

Thanks for the other posts, it seems there is no standard practice when it comes to folding back/twisting/neither. Only thing I might want to do with the repositioned socket is leave a little more length of exposed red/black.

James

 

[Qedelec]

As a rough guide anything from 2.5mm down should be doubled to give the terminal screw something to 'bite' into. If two or more wires are into the same terminal post then there is no need to double no matter what size cable is terminated.
No copper of live cables is to left exposed.
Screw must not clamp onto insulation.
All cpc's (earth's) must be identified with green/yellow sleeving or tape.
All switch wires on lighting circuits most be identified as such with red/brown sleeving or tape.