Drilled through cable in wall

[Maggie30]

Hi I'm wondering if someone can help. I wanted to put up some shelves in my kitchen so I used a wall voltage tester to see if there was any live cables behind a wall before drilling and it showed none (I know the tester definitely works).

When I was drilling a spark came out of the hole and tripped an mcb in the comsumer unit which powers the fridge, washing machine, dishwasher and hob. I dug into the wall and found I had gone straight through a cable twin and earth cable. So I repaired it using a maintance free box. When I turned the tripped fuse back on everything in the kitchen works again.

However the cable I repaired has no live coming through it as I tested it with both my wall tester and my TIS 851 Voltage & Continuity Tester. It has continuity between the neutral and earth but doesn't if I turn off the main consumer unit switch.

What I'm trying to figure out is, is it possible that it is not live and tripped because when drilling the neutral and earth like this guy explains in this YouTube video...

Any help or advice would be very much appreciated. Thank you!

 

[Harry Bloomfield]

What I'm trying to figure out is, is it possible that it is not live and tripped because when drilling the neutral and earth like this guy explains in this YouTube video...

If you mean the RCD /RCBO tripped, they can trip do to an imbalance of current flow, comparing L to N. The N often has a small amount of voltage on it, when compared to the E, short the N to the E then current will flow, enough to trip an RCD.

RCD's usually protect several circuits, RCBO's are a combined RCD and MCB, protecting a single circuit.

 

[EFLImpudence]

When I was drilling a spark came out of the hole and tripped an mcb in the comsumer unit which powers the fridge, washing machine, dishwasher and hob. I dug into the wall and found I had gone straight through a cable twin and earth cable. So I repaired it using a maintance free box. When I turned the tripped fuse back on everything in the kitchen works again.

Ok. Did you have enough wire to pull and join?

However the cable I repaired has no live coming through it as I tested it with both my wall tester and my TIS 851 Voltage & Continuity Tester.

But you say everything is working again.

It has continuity between the neutral and earth but doesn't if I turn off the main consumer unit switch.

Well it wouldn't. You are disconnecting the Neutral by turning off the main switch.

Have you tested for voltage between L & N and L & E?

What I'm trying to figure out is, is it possible that it is not live and tripped because when drilling the neutral and earth like this guy explains in this YouTube video...

I would say NO if I understand correctly.

 

[Maggie30]

Ok. Did you have enough wire to pull and join?


But you say everything is working again.


Well it wouldn't. You are disconnecting the Neutral by turning off the main switch.

Have you tested for voltage between L & N and L & E?


I would say NO if I understand correctly.

Not enough wire to pull and join as I drill twice into same cable (First hole drilled through the cable didn't trip anything). I actually used 2 x maintance free box plus extra length of twin and earth to join.

I'm guessing that cable isn't powering the kitchen items which is why I'm trying to figure out how it tripped the kitchen fuse.

Tested for voltage between both L & N and L & E and no voltage at all. Only continuity between N & E

Are you saying that NO you don't think it ever was live?

Is it possible that the live isn't connected to the consumer unit and what Harry said could be happening?

Thank you for your quick reply BTW!

 

[EFLImpudence]

Not enough wire to pull and join as I drill twice into same cable (First hole drilled through the cable didn't trip anything). I actually used 2 x maintance free box plus extra length of twin and earth to join.

Ok.

I'm guessing that cable isn't powering the kitchen items which is why I'm trying to figure out how it tripped the kitchen fuse.

Tested for voltage between both L & N and L & E and no voltage at all. Only continuity between N & E

Ok.
You said it was an MCB but a fuse reacts the same. I.e only on the circuit involved will be disconnected.
However, if it was an RCD that tripped, then several circuits could be switched off.

Are you saying that NO you don't think it ever was live?

No, I was saying it is not possible for an MCB (which you said) or Fuse to trip by touching N & E; that would be an RCD if that is what happened.

Is it possible that the live isn't connected to the consumer unit and what Harry said could be happening?

Anything is possible.

 

[Maggie30]

Ok.


Ok.
You said it was an MCB but a fuse reacts the same. I.e only on the circuit involved will be disconnected.
However, if it was an RCD that tripped, then several circuits could be switched off.


No, I was saying it is not possible for an MCB (which you said) or Fuse to trip by touching N & E; that would be an RCD if that is what happened.


Anything is possible.

I've attached photos so you can see the exact one that tripped when I drilled the holes.

Before I opened up the wall to locate the cable I drilled I was able to turn it back on without anything tripping.

 

[EFLImpudence]

I've attached photos so you can see the exact one that tripped when I drilled the holes.

Before I opened up the wall to locate the cable I drilled I was able to turn it back on without anything tripping.

Ok. That is an MCB so would not have tripped by just touching N & E with the drill, so you must have touched L & E thus causing the spark.

SO now you have repaired the cable do the appliances you mentioned stop working when you switch off that MCB?

 

[Maggie30]

Ok. That is an MCB so would not have tripped by just touching N & E with the drill, so you must have touched L & E thus causing the spark.

SO now you have repaired the cable do the appliances you mentioned stop working when you switch off that MCB?

I found where the continuity is coming from now. I have a fused plate in my kitchen which has one called washing machine. However my actual washing machine has its own fused switch elsewhere in my kitchen.

I tested the fuse and it's dud so I turned off the switch and there's no continuity in the cable but when I turn it back on there is. I have no idea where that cable runs to as its never been used. Should I just leave it unused or put in the fused and test for live just to see?

 

[Maggie30]

Ok. That is an MCB so would not have tripped by just touching N & E with the drill, so you must have touched L & E thus causing the spark.

SO now you have repaired the cable do the appliances you mentioned stop working when you switch off that MCB?

OK so I put the fuse it just to see and now the cable is live.

My wall voltage tester is also picking it up which means that the fuse in the kitchen was blown before I even drilled into the wall.

Now question is do I just leaving the washing machine on the plate with no fuse or go looking for where the cable could be going?

 

[EFLImpudence]

OK so I put the fuse it just to see and now the cable is live.

Ok.

My wall voltage tester is also picking it up which means that the fuse in the kitchen was blown before I even drilled into the wall.

Perhaps - but you said it sparked.

Now question is do I just leaving the washing machine on the plate with no fuse or go looking for where the cable could be going?

Not sure what that means.

SO now you have repaired the cable do the appliances you mentioned stop working when you switch off that MCB?

 

[Maggie30]

Ok.


Perhaps - but you said it sparked.


Not sure what that means.

Yes I said it sparked and now I've done some more tests with the wall voltage tester you are most likely right it must or could have been live as its not always picking up the voltage.

The photo of the washing machine (label) switch I posted, I previously thought the fuse wasn't working which now after doing more tests I can't be 100% sure. However if it did blow after drilling I haven't noticed anything not working within the house.

When I switch off the MCB it turns off the fridge, washing machine (the separate fused switch not not the plate) and everything on the plate (the photo I sent).

So the cable which I drilled through is going from the washing machine (label) on the plate upstairs somewhere which is very strange (to me anyway).

 

[EFLImpudence]

Yes I said it sparked and now I've done some more tests with the wall voltage tester you are most likely right it must or could have been live as its not always picking up the voltage.

They are not really reliable.

The photo of the washing machine (label) switch I posted, I previously thought the fuse wasn't working which now after doing more tests I can't be 100% sure. However if it did blow after drilling I haven't noticed anything not working within the house.

Ok.

When I switch off the MCB it turns off the fridge, washing machine (the separate fused switch not not the plate) and everything on the plate (the photo I sent).

Right, so the cable must be live.

So the cable which I drilled through is going from the washing machine (label) on the plate upstairs somewhere which is very strange (to me anyway).

Is that not just coming from the consumer unit?

 

[Maggie30]

They are not really reliable.


Ok.


Right, so the cable must be live.


Is that not just coming from the consumer unit?

Yes I agree they are not reliable.

What I believe is there is a cable coming from the consumer unit (the MCB I sent a photo of) into the plate which has the 4 switches on (which I sent photo of... cooker hob, dishwasher, washing machine, hob).

Then the cable which I drilled into is going from the washing machine (label plate) behind all the kitchen tiles up along next to the kitchen window, up until I'm not sure.

I'm attaching 2 photos of before I added the 2 maintance free boxes and after.

 

[EFLImpudence]

What I believe is there is a cable coming from the consumer unit (the MCB I sent a photo of) into the plate which has the 4 switches on (which I sent photo of... cooker hob, dishwasher, washing machine, hob).

Yes, there must be if that MCB turns off the appliances. One says cooker hood and another hob.

Then the cable which I drilled into is going from the washing machine (label plate) behind all the kitchen tiles up along next to the kitchen window, up until I'm not sure.

Do you mean the switch and fuse panel when you say label plate?
If so, as I said before; is that not a cable to the switches from the CU?

I'm attaching 2 photos of before I added the 2 maintance free boxes and after.

Ok. Can you repair it without burying the JBs in plaster?

 

[Maggie30]

Yes, there must be if that MCB turns off the appliances. One says cooker hood and another hob.


Do you mean the switch and fuse panel when you say label plate?
If so, as I said before; is that not a cable to the switches from the CU?


Ok. Can you repair it without burying the JBs in plaster?

Yes switch and fuse panel. That is from the CU

No I need to bury the jbs in the wall as the shelves still need to go up.

I'm not a person to give up on my original goals long as its safe!

I'm keeping it open for another week or 2 before I seal them in the wall just incase we find there is an actual issue.

You have actually been super helpful and I really appreciate you questioning me on everything... I'm guessing lots of people hate that! For me it makes me question myself and double triple check everything which can lead to issues!

Thank you for that