slight disaster

[flashbanger13]

I was attempting to tighten up a loose backbox in a house today. It's located in a lathe and plaster wall. I drilled a screw through the centre hole and noticed something behind it. Upon removing the backbox i discovered a cable running behind it with a nice new screw sized hole in it!

What can i do to remedy the situation? Is it acceptable to cut out the damaged part, strip the cable and crimp it behind the backbox?

please help!

 

[JACKC]

Yes if its crimped and with the correct size crimps, blue 2.5 and red 1.5. sleeve the earths and then can be plastered over. If you use a terminal box, has to be accessable to recheck tightness etc. I wrap crimps with self amalgamating tape so water from plaster does not get in.

 

[Adam_151]

Sink a deeper backbox in, and make crimped connections in the back of it?

 

[tim-spam]

Why should the terminal in a JB come loose and a crimp remain tight?
I recently came across a JB under a bedroom floor that has been there for around 30 years, and the terminal screws were all tight. I have now secured this juction box to a piece of wood secured to the joists (it was just resting on the plasterboard when I found it) and clipped the cables to this piece of wood. According to the books I've read, this is supposed to protect the wires from being pulled out of the terminals. The only problem with this is that it effectively adds nothing to the security of the joint, because the force required to pull the cables from the clip is vastly less than that to pull the wires from the terminals - I did a little trial on a spare JB and length of wire. I've still clipped the wires as it looks neater.
By the way, the house was wired by the MEB, and the previous owners were absolutely not DIY'ers in any sense, so I guess that means that this JB was their work - just goes to show.....

 

[JACKC]

Regs state access for maintenance, need to be able to get to screws etc, so not ideal to plaster over. Crimps were developed by NASA for secure way of joining. No need for maintenance so can plaster over.

 

[PompeySparks]

A crimped connection crushes the crimp and conductor together under emmense pressure (use proper ratchet crimpers!) and cannot be undone where as terminals were designed to be undone - be it on purpose for testing (one advantage) or accidentally over time with expansion and contraction of brass due to current flow, general vibration or shoddy workmanship (left loose!)

I hate this idea that there is something 'not proper' about crimping and the accompanying view that connector block (rubbish stuff!) is somehow equal/better!?

I will admit that crimping is not a perfect solution, but it is realistically the best available. It is only a hazard if you a.) use dirty joints b.) use a cheap set of manual crimpers that don't make a tight enough connection!

 

[tim-spam]

I didn't say (or mean) that there was anything improper about a properly made crimp joint, but was merely pointing out that there is also nothing wrong with a properly made screwed joint either. The coefficient of thermal expansion copper and brass is virtually identical, and in a house the amount of movement likely to cause loosening of a screwed joint is insignificant, so a properly tightened joint should stay that way. In addition, I doubt whether a crimped joint is made under any more pressure than a screwed joint - both types of joint make indents on the wire cores if properly made.
My guess is that the requirement to inspect screwed joints has more to do with the fact that you can, rather than for any other reason.