Digging up concrete floor containing main domestic electricity supply cable??

[Sylvie3]

The concrete floor in my hallway needs to be removed. The main electricity supply cable from the street runs under the hallway and comes up through the concrete to the consumer unit below the stairs. It looks like the concrete was poured after the cable was put in.

I'm worried about hitting a cable while drilling/breaking up the floor. I've spoken to UKpowernetworks to try and get the electricity supply temporarily disabled during works and they've quoted nearly £3000 and many months of waiting to disconnect and apply for a new connection!

How can I break up this floor safely?? Is it enough to hire/buy a detector and mark out the path of the cable?

I'm also worried that the cable will be damaged after decades encased in concrete. If we dig up the floor and the cable needs replacing who do we contact?

Grateful for any help!

 

[Doggit]

You know where the cable comes up, and it's reasonable to assume that the cable will run fairly straight to the front door, but it may not. But you have a starting point where the cable comes out of the floor, so you start from that end with the breaker, and you use a club hammer and bolster to edge along about half an inch away from the cable as you go. I think you can hire the commercial testers, but it's not going to give you a precise location, just a fairly close one. But the cable should fine.

 

[JohnW2]

... I'm also worried that the cable will be damaged after decades encased in concrete. If we dig up the floor and the cable needs replacing who do we contact? ...

The same people you asked about temporarily disconnecting the supply, and probably also your bank manager, since you couldn't be back into the ££££ problem

Kind Regards, John
Edit: typo corrected

 

[flameport]

A more sensible option would be to have the supply relocated to an external cabinet, which will disconnect the cable under the floor.
You can then remove the floor without any danger.
Relocation should be a much cheaper option than disconnection and subsequent reconnection.

If we dig up the floor and the cable needs replacing

There's the problem - if hacking at the floor damages the cable, not only will you have to pay a non-trivial amount to have the supply repaired, you could be without power for an extended period of time.

 

[securespark]

bank Edit: typo corrected

if hacking at the floor damages the cable, not only will you have to pay a non-trivial amount to have the supply repaired, you could be without power for an extended period of time.

Not to mention a potentially life-threatening explosion...

 

[Lectrician]

A more sensible option would be to have the supply relocated to an external cabinet, which will disconnect the cable under the floor.
You can then remove the floor without any danger.
Relocation should be a much cheaper option than disconnection and subsequent reconnection.


There's the problem - if hacking at the floor damages the cable, not only will you have to pay a non-trivial amount to have the supply repaired, you could be without power for an extended period of time.

That’s what the quote was for.

If the cable is an old PILC cable, I wouldn’t entertain breaking around it.

How old is old?

My supply cable appeared through my garage floor. After breaking around the base of the cable a few inches, it revealed a duct.

 

[Sylvie3]

Thanks for the suggestions! I will try to find out what sort of cable it is, and look into relocation. Why is a PILC cable particularly bad?

As to how old - it's presumably the original cable (house built 1880s so early/mid 20th century cable?). The house has 1940s round light switches (!) The concrete probably went in the 1990s so definitely older than that.

 

[aptsys]

Thanks for the suggestions! I will try to find out what sort of cable it is, and look into relocation. Why is a PILC cable particularly bad?

It's typically quite fragile after being installed for 50+ years. If it's bent or receives any impact, it's not difficult to piece the paper insulation resulting in lead all over your face.

Even if you have PVC installed, you should take care. Take a photo of the area and post on here, we can quickly identify.

 

[ban-all-sheds]

UKpowernetworks to try and get the electricity supply temporarily disabled during works and they've quoted nearly £3000

A more sensible option would be to have the supply relocated to an external cabinet, which will disconnect the cable under the floor.
You can then remove the floor without any danger.
Relocation should be a much cheaper option than disconnection and subsequent reconnection.

That’s what the quote was for.

Sylvie - if what they actually quoted you for was relocation to an external cabinet, and not whatever you thought you wanted, ask them how much of the works are contestable - if you've got the ability, or people on site with the ability, to dig up concrete floors I'm sure the same skills can be turned to digging a trench outside for a new service cable.

FYI - "temporarily disabled" - there is no switch they can flick - they would have to dig to get at the cable outside, and then physically cut it, and later join it, and all the time it would be live. It needs a team of people, with specialist training and tools etc.