How deep through concrete

[Yanni]

I’m having the garage wired by my electrician.
But he wants me to dig the trench.
At the end of the trench there is concrete, how deep do I need to go into concrete as it is such a pain trying open a grove for the Trunking.
It is a 4m armoured cable he uses.

He told me it doesn’t matter how deep as it is RCD protected. Can I have another opinion pls.
I can dig the soil part up to 450mm no problem but it is the small section in the concrete that bothers me.

 

[JohnD]

How thick is the concrete?

If thin, you can use an ordinary angle grinder, or even a big hammer, but you can hire a wet diamond cutter that will be quicker and less dusty.

You can also drill a diaginal hole, from inside the building against the wall, but you will need a big drill.

 

[plugwash]

The regs don't specify a depth, they just say burried cables need to be deep enough to avoid any reasonablly forseable disturbance to the ground.

The question I would be asking is whether the cable is likely to be there longer than the concrete? if it will then you really want the cable to be below the concrete rather than embedded in it.

Do you know how thick the concrete is? would digging under it from the side and then drilling through be an option.

 

[SUNRAY]

Personally I'd have drilled a hole through the slab right against the wall and as angled as possible as John says, then dig a pit in the soil and make a horizontal hole in the soil to meet the vertical.

Much easier and neater.

If you (or your electrician) don't have a big enough drill, drill several holes through the slab in a circle and parallel then use a piece of scaff pole as a round chisel.

 

[Adam_151]

As above, I'd drill downwards at an angle and out the side of the slab.

I went to a fault where the cable routing was as per OPs initital plan, but a bit closer to the frame of the door, it was stated that since the chap who was fitting a new garage door was using tranny and grinder off garage supply that it kept tripping that evening.

Went round, was tripping MCB as well as RCD, you can guess the rest, fixing hole for a bracket off the floor slab perfectly through the centre of the SWA

 

[Sureitsoff?]

is there lawn to the left of the garage in the pic? if yes then could you run the cable around the garage corner and come in through the left hand wall rather than the concrete

 

[SUNRAY]

is there lawn to the left of the garage in the pic? if yes then could you run the cable around the garage corner and come in through the left hand wall rather than the concrete

good call