Did we touch a wire?

[GillObrien]

Hi all,

We just put a bracket up for a light fitting on our ceiling. The ceiling is thick plaster sheets hung on long screws I think (I.e. there are no battens behind, in the void you see right across and it is just punctuated with metal "screws" or "posts").

We generally have hooks in our ceiling fittings that are attached to the actual concrete ceiling above, but not here.

We checked for wires and metal "screws" then drilled. When I put the tension testing screwdriver (the light up one) against the bracket I get nothing. When I put the tension checking device against it (picture below) it shows the symbol for tension being present.

is it possible that we touched a wire in the void? With a dull ended drill bit? The wires are loose so they would normally just have moved and anyway there shouldn't have been any where we drilled. We were limited in where to put it as the detector was showing the metal posts and wires elsewhere.

Should we worry at this point?

Thank you all!

 

[opps]

You seem to be using the word tension incorrectly.

Your screwdriver is not particularly accurate.

I am not an electrician... you were able to screw the mounting bracket without getting a shock.

spend less than a tenner on a multimeter and you will be able to find out if all is good.

 

[GillObrien]

The electricity was off . I used tension because I am in France and that is what it says on the tool. It translates to voltage I think.

If I had a multimeter would I understand what it was telling me? The tool usually tells me the voltage e.g12v and displays neutral or other depending on what it is touching. In this case it displays nothing except the symbol indicating there is voltage present.

I think I will turn of the electricity and remove it just in case.

 

[flameport]

the tension testing screwdriver (the light up one)

Those devices are useless.

They can show voltage where there is none, and show nothing when there is. Don't rely on it for anything.

 

[blup]

if the volt stick has identified voltage, assume it is present, a flexible inspection camera will show whats there and whether you have drilled into a cable.

Blup

 

[johnny2007]

I would switch electricity off, enlarge the hole slightly with pliers without damaging the cable and put my finger in there to make sure screws have not gone into cables.
Unless you have a flexible inspection camera as suggested above.

 

[Ragnar_AT]

A multimeter isn‘t much better than that screwdriver. Get a two-pole voltage tester that claims it can trip RCDs. One probe goes onto the neutral (blue wire), the other goes onto the bracket.

Multimeters usually have a high internal resistance to make sure they don‘t influence the circuit you‘re measuring. In delicate electronics with low voltages (millivolts or a few volts) that’s crucial. In mains wiring that means they will not only show you actual mains voltage but also phantom voltages from capacitive coupling (two wires close enough to each other act like a small capacitor). As soon as you connect even a small load like that tester the phantom voltage goes away. For the same reason those neon screwdrivers can give false positives. And if you‘re well insulated, e.g. standing on a dry wooden ladder, they can give you false negatives. Their only real purpose is determining if the blue wire is actually the neutral as it‘s supposed to.

Another test would be connecting an LED or incandescent bulb to the neutral and the bracket. If it lights up the bracket is most definitely live.

 

[GillObrien]

Thank you all. I had a look at it this morning. I couldn't see any wires that we could have touched, all the wires were still free in the void and out of the way. The bracket was no longer showing voltage, so I think that I had used the tester wrongly (I admit to not reading the instructions fully before). I was more careful to keep it still on the bracket and put my other hand on the wall as instructed.

I fitted the light and tested it - there is no reading on any part of the light fitting.

Thank you all for you help!

 

[blup]

Those volt sticks flash to show they're working, not because they have detected "tension".

Blup

 

[GillObrien]

@blip That would have avoided a lot of worry if I had known that!