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I was trying to fix a nail on my wall and it seems that I may have ran the nail into a wire. Pulling the nail back causes the lights in my room to go dark. I pushed it back in and my room seems fine, and, I plan on getting it fixed soon.

However, should I take any precautions before the time it actually gets fixed? The nail I was using was about 5-7 cm.

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Shut the circuit off. Leave off til fixed.

You took a chunk out of the wire, if not severed the whole wire. That means it's thinner, or out of contact entirely.

If it's thinner, that means current is squeezing through a narrow part. This will make the wire hot there. It could get hot enough to ignite a fire on the wrong side of the walls.

Of if the wire is cut entirely, or passing through the nail, it is bound to start arcing. Arcing makes a tremendous amount of heat - it will heat up much, much faster than a nicked wire, and could start a fire going in less than a minute.

Drywall is a fire-stop. That means, fires which start in between the walls are hard to detect. They can become "fully engaged" (turned into a pretty big fire) before you even detect it.

And then what? It's almost impossible to fight a fire on the wrong side of the drywall, unless you are a pro fireman who hatchets drywall every day. By the time they arrive, the fire will be so engaged that they'll have to wreck the place to save the structure at all.

How to avoid it?

Obviously, this is a common risk. Every country has an electrical code (really, although it is sometimes not enforced pre-accident) and many electrical codes provide provisions for how to resolve the conflict between wire damage and nailing things to walls. For instance some countries require metal plates to guard cables, or that wires be placed a certain depth in the wall - that creates a "safety zone" where one can nail with confidence as long as your nail is short, and you don't power through a guard plate.

It's best to learn the convention in your country, and follow it.

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  • 12
    The OP gives 5 to 7cm for the length of the nail that is 2 to 2.5" in old money....
    – Solar Mike
    May 29 at 5:08
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    Given the OP used cm not inches, it’s possible they’re outside the US, and there would be different requirements for wire depth.
    – Tim
    May 30 at 16:34
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    I would not make ANY assumptions on regulations in other countries. I am in Europe and aware of at least a few countries' DIFFERENT practices, and I have not seen anything like a minimum depth applied. In some cases, other rules keep you from putting nails in the wrong places, some use other technical means to prevent damage, and generally, you better check beforehand. In fact, even rules for maximum depths (<40mm!) in carrying walls exist. So I can fully support your first paragraph, but the second one should be considered false unless you specify whose rules you are talking about.
    – jerry
    May 31 at 8:08
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    ... and BTW, the OP is from India.
    – jerry
    May 31 at 8:09
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    @jerry: E.g. I'm in Germany, and AFAIK (I'm no electrician) we do have maximum depth into the wall, which in some cases can be as shallow as allowing <= 10 mm slit depth. We do have normed zones where invisible electrical intallation is supposed to go (3 horizontal stripes 15 - 45 cm and 100 - 130 cm above the floor and 15 - 45 cm below the ceiling, vertical stripes 10 - 30 cm beside doors, windows, corners). However, I'd always recommend to check with a cable finder, and the older the installation the more important that recommendation. These norms have not been around forever. May 31 at 8:52
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It needs to be fixed now. That nail has contact with electricity and anyone touching it that and is also grounded can die. It can also heat up the wire and cause a fire. Turn off the breaker for that circuit until it is fixed.

Do not leave until it is fixed. It is dangerous to you and your house. Turn off the breakers one by one until the light goes off. Do not trust the switch.

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  • +1 for the point about using the circuit breaker. May 30 at 11:54
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    It's worth stressing that the nail might be in a wire between the circuit breaker and the switch, in which case turning the switch off won't disconnect the nail. The circuit breaker MUST be turned off. May 30 at 19:17
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Something no one else said, placed here for future readers;

Yes, you should worry. Do not do this ever again. If you need to put pointy metal things in walls, get a cable tracker/wire finder/wire tracer device and find out where the cables are before you start. Mark them on the wall. Draw a diagram. Photograph it. Write it down.

As a rule cables installed by qualified electricians in well-regulated countries run tidily vertically and horizontally so you know where to start. The house I am living in right now was a self build, and the builder ran the cables diagonally to save money. May he burn in perdition.

Edit: where I live - yes, Germany - walls tend to be solid masonry. Your cables cannot just dangle around behind the plaster. Though I have seen pre-fab houses where the space is full of insulation, not air, and the cable running inside the wall may not be fixed 100% securely, but it's clipped in place, and yes, it runs orthogonally.

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    "As a rule cables run tidily vertically and horizontally so you know where to start" Sorry, but again I need to comment on dangerous generalizations. This is indeed a rule - IN GERMANY where RedSonja lives.
    – jerry
    May 31 at 8:54
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    @jerry It is also the rule here in the UK, but rules can and do get broken. I've seen cables run diagonally before.
    – OmarL
    May 31 at 12:54
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    @OmarL: Yes, but neither German nor UK rules apply to the OP in India nor many others reading this. I have often seen cables just loosely thrown behind plaster walls - and, as scary as this sounds, that is pretty effective against damage from nails with the cable happily moving aside - unless you use a nail gun. Not saying I like it but that's how it is.
    – jerry
    May 31 at 13:13

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