Cable in concrete trench corroded

[maccaandy]

Hi,

A few years ago I had some cables run from my fuse board to my kitchen. The cables were laid inside my house through the concrete base. There was a long trench dug through the house, and the cables laid into it. Now, a few years on, I've had a qualified electrician confirm that the cables which were laid have corroded and need to be replaced.

Does anyone know what the regulations are with laying normal PVC cable in concrete? Should it have been put in conduit to protect it? The qualified electrician I recently had said I could claim against NAPIT for incorrect installation, but I need to work out if it was actually incorrectly installed or not. I've attached a picture of the cables going straight into the ground.

Does anyone have any advice on this please?

 

[Dustydazzler]

Cable installed like that buried straight into the concrete floor is rough a badgers arse but for PVC to rot away would take years and years from my experience.

 

[DPG]

I can't believe they've all corroded. Did he test them all to prove this? Are you having issues electrically? Why is the electrician looking at these cables?

 

[snowhead]

It would be interesting to see the damage on the "corroded" cables when they are removed.
Were they surrounded in concrete / screed or just covered over with it?

It's not a regulation you need to look for, I doubt you'll find one that says thou shalt not bury pvc cables under the floor with or without concrete / screed surrounding them, it's the cable manufacturers spec for the cable that you need.

For example from Cleveland Cables re twin and earth;

Used for fixed installations in dry or damp premises clipped direct to the surface, on trays or in free air. Where mechanical protection is required, it can be laid in conduit or trunking.

It doesn't say must not be direct buried or covered with sand cement or plaster.

Putting the cables in underground ducting would have been a better solution and made it easier if the cables failed for any reason.

 

[maccaandy]

It would be interesting to see the damage on the "corroded" cables when they are removed.
Were they surrounded in concrete / screed or just covered over with it?

It's not a regulation you need to look for, I doubt you'll find one that says thou shalt not bury pvc cables under the floor with or without concrete / screed surrounding them, it's the cable manufacturers spec for the cable that you need.

For example from Cleveland Cables re twin and earth;

Used for fixed installations in dry or damp premises clipped direct to the surface, on trays or in free air. Where mechanical protection is required, it can be laid in conduit or trunking.

It doesn't say must not be direct buried or covered with sand cement or plaster.

Putting the cables in underground ducting would have been a better solution and made it easier if the cables failed for any reason.

ok. thank you for this. that's useful.

 

[maccaandy]

I can't believe they've all corroded. Did he test them all to prove this? Are you having issues electrically? Why is the electrician looking at these cables?

Hi, yes the fuse kept tripping and eventually wouldn't even turn on. He tested the cable and it shorted between earth and live. It happened to another cable in the same trench last year, but we managed to by-pass it.

 

[buzzlightyear]

The qualified electrician I recently had said I could claim against NAPIT for incorrect installation, but I need to work out if it was actually incorrectly installed or not. I've attached a picture of the cables going straight into the ground.

That horse has bolted. How can you claim against nupit, the electrain should advised you better, or did you agree.

 

[brianmoooore]

Are there any cracks in the concrete? A much more likely scenario than corrosion, is for the cables to have been sheared as a result of concrete movement.

 

[mainline]

Can usually get away buried in a wall, but not in a concrete floor, like already said it usually takes yrs before it goes wrong, but as you already now know that's not always the case.

 

[buzzlightyear]

I have seen a lot of cables in wooden trunking buried. Not a good idea buried.
In concrete.

 

[brianmoooore]

Are there any cracks in the concrete? A much more likely scenario than corrosion, is for the cables to have been sheared as a result of concrete movement.

Never come across a cable damaged like this, as I've never dealt with one buried directly in concrete, but I have seen it with pipes.
One particular job, I was called there to sort a non heating immersion heater, so I expected to find a dud immersion 'stat or burnt wire to it. Turned out to be a sheared hot water pipe in the kitchen floor, under the DPM, which was dumping water into the ground faster than it could be heated.

 

[mainline]

Had to deal with central heating copper pipes buried in concrete with an oak block wooden floor on top lasted around 8 years before the centre of the floor lifted about 4 inches, ended up being an insurance job costing £1000s in the end

 

[maccaandy]

Thank you for the replies. I'll try and make sure the people doing the work don't disturb the cable so can see what has actually happened to it.

 

[mainline]

You could quote section 522

 

[maccaandy]

That's very handy ineed. Just found a little guide about it online. There absolutely hasn't been this consideration done when installing the wires. https://dms.niceic.com/0000003685.pdf

 

[brianmoooore]

I have seen a lot of cables in wooden trunking buried. Not a good idea buried.
In concrete.

Wooden trunking above DPM should be fine. Used to be a common installation method for copper pipes in floors - two lengths of 2X1 batten laid on edge, with a 10mm plywood cover on top, then screed laid flush with the top of the plywood.

 

[cliffed]

Hopefully there’s a duct somewhere in the ground if you can find it….you could dig around the cabling & see if you find the duct & look at the cabling to see if they are damaged

 

[OnlQQker]

Mixture of new and old cable by the looks of it, and is that a 28/22mm copper pipe dropping into the floor?

If so is it gas?

 

[Midwest]

PVC cables buried in concrete. Doesn't seem like a good design. Last time I did some concreting, I ended up with very chapped hands.

 

[7029 dave]

I have provided 2 new circuits chased in floor when my mates parents had their kitchen revamped.
His dad was an architect and instructed me to do it, that your route. lol Was not keen but hey he was the boss never had any comebacks done that job mid to late 80's. Plastic conduit used.
His parents are long gone RIP and he now lives in the USA