Getting power to my island

is there no access below the floor? (I assume not, since you mention footings...) but if there is, is there some reason you cannot drill a single hole and run the wire below grade?

Slab construction means just that: it's a slab of concrete, bedded in gravel, directly on the ground -- IOW, no access underneath.

Will the island have structures of any kind, like a cabinet above it? Anything which might give you a post which could be hollow, through which you could run conduit to the ceiling?

As far as grooving the slab, I see no reason why that couldn't be done. Just check with your local building inspector for code regulations. Sometimes, just reading the code can give you ideas for good ways to achieve your purpose. Granted, codes are full of "thou shalt not", but they also contain "thou oughta consider this idea".

Ah.

I have a friend who has (well had) poured floors of concrete in his old house... come to think of it, in his new house (which we joking call the bunker.... the whole thing is concrete) as well.

We had a heck of a time drilling through it (from the basement) to run electricity for a garbage disposal.

Had a masonry bit, but just a regular drill... hammer drill might have helped.

With no crawlspace, you have limited ways to go. Trench as OP mentioned(if it's allowed by code) Raised floor (if it didn't present too many other problems) Drop from above.

Wish I could add more... but i'm not a pro.

I think that you will find that it will be much easier to remove the concrete if you make your cuts all the way through the concrete, then just smack the concrete with a sledge hammer a couple of times in 3 or 4 spots. Once the first piece is pried out it's all downhill.

I agree with Volts. Go down to the full thickness of the slab. Don't remove any wire mesh from the trench as you will want that to help the new concrete tie in with the old.

You can use PVC conduit underground, but I always suggest stubbing up through the concrete with a rigid metal elbow. The point where the conduit emerges from the concrete is always the most vulnerable to abuse and consequently breaks after a few years. You can mount a junction box on the rigid stub-up and convert to non-metallic or armored cable to facilitate the installation of receptacles throughout the island. You can also adapt the rigid elbow to EMT for better protection of the wires in the island.

Table 300.5 in NFPA 70 can provide some insight.

John Grabowski

Look at FCC (flat conductor cable). It is wide, but thin copper conductors that are attached (glued) to your slab and the floor covering, tile, carpet, etc. is then placed over it. FCC is available in 12 and 10 gauge (20 or 30 amp capacity). The stuff isn't free but it is a lot better than trenching in concrete. I've had several of these installed in my conference rooms to bring substantial power for large projectors and other equipment to large conference room tables located in the center of the room. As I recall the last ones I signed off on came from Hubbell.

A quick Google search only yielded this but they do exist and work well.

RB

chibiabos wrote:

I didn't think FCC cable was used much anymore. I spent a few years on my knees with that stuff in one office building that I serviced. The whole building was wired that way. Mostly Thomas and Betts. It's expensive and has specific code requirements for the installation. For instance, the floor covering must be removable tiles that cannot be larger than 36" square. It is not approved for residential use. The floor base must be extremely smooth as any dimples or bumps can cause damage to the cable. It is also available for data and phone wiring. I would only recommend its use as a last resort.

John Grabowski