Here we have an example of one of the problems of our shallow light-switch boxes (this is the standard depth of 1/2 inch).

The arcing which has taken place here could have been due to a loose wire or skinned insulation, but from the location of the marks, my money is on a conductor being trapped and nicked as the switch was jammed into the box.

Oh, and there's also a code violation here as well.

Paul,
whats that stray 6491x doing in that box?

Britspark

Hmm,
I'm guessing that the Code violation has something to do with either the box not being Earthed or if that 3-Core is a 2-Way switch wire, the green wire should be a different colour.

I wish we could get ahold of cable with colors like that here for 240v circuits and switch loops. No more recoloring white wires!

Funny you don't have it there in the USA, but they do make a 12/2 Red/Black NMD-90 for the Canadian market, and it is rather common in the home centers I've been in. It was I think originally made for wire in 240V heaters, but I have seen it used for other 240V loads and switchloops.

Larry you can get it here, just no one stocks it, and rarely ever uses it because tape or 3-wire is much faster, and cheaper than special order wire.

The violation has to be the single red wire going up. What was it for? Added three way?

The green was actually connected to the earth terminal on the box -- I'd already removed it before taking the pictures (it's actually the bare earth conductor with green sleeving on the end).


For the benefit of non-UKers:
6491X = Single-insulated cable of the type normally pulled into conduit.

You've got it! The added single was on the switch common with the red/black in the cable used as travelers.


Strictly speaking that black wire should have been remarked red, as black is (was) our neutral color.

We have cable with two red conductors, intended specifically for use on switch loops, although in my experience it's very rarely used.

Unfortunately neither red/black nor red/red will be available for much longer as we change over to the new brown/blue color code.

That single 6491x cable should be a double insulated single. If that was used, and the box was wired neatly and laid in carefully the job would of been ok.

The real problem, of course, is stamped on the inside of the box:


j/k!

LOL!

"Made in England" is the warning label on Lucas electric components.

I've had light switches where some genius had split a length of zip cord in half, wrapped one wire in elektric tape and embedded it in plaster to provide a neutral for a receptacle... right next to a straight run of conduit...

Paul,
I thought that you use residual current devices at the main over there. If that is true how was there enough current to do that damage?
Don

resqcapt19,

We only have RCD's protecting socket outlets & it's good practice to have an RCD on the electric shower circuit too. It is common practice now to fit a 'split load' board, which means you have the sockets & anything else needing an RCD on the RCD side of the board and the lighting and other stuff such as immersion heater, boiler etc on the non RCD side. Most older installations did not have an RCD at all. On installations where the earth is provided solely by an earth rod or 'electrode' then the whole installation needs to be covered by a 100mA time delayed RCD with the sockets having additional protection via a 30mA RCD. At a guess the installation in question here was via an older style "Wylex" brand rewireable fuse box & probably has no RCD covering the installation.
The switch looks like it was badly terminated, the outer sheath was brought too far into the box (messy) and the conductors were stripped off too much causing the copper to touch the case. I don't like 16mm back boxes as there just too tight, I would rather spend 2 more mins and get a nice 25mm box in there.




[This message has been edited by Out Of Phase (edited 11-06-2005).]