Horse stalls. Beam and post construction , 132 X 24. Roof over ½ of area, or 132 X 12. Metal siding on back wall as well as 12 on the 2 ends. 10 stalls and 1 tack room, each 24 X 12, with tack room in middle of building. Stalls utilize knock down corral fencing on all sides. Tack room framed up with plywood front and sides. Concrete floor in tack room, and concrete continues out 12 from tack room to front of stalls, and includes a frost-proof water faucet (fed with plastic pipe underground). Concrete slab was poured using fiber instead of wire mesh. Proposed: Install 60amp 4-wire panel fed from meter/disconnect on a remote pole. Loads include 1 150watt light located in the middle of each wing (each wing consists of 5 stalls) and 1 light and 2 gfci outlets in tack room. PVC conduit will be wiring method, with snap covers on switch and outlets. Grounding electrode system will consists of two 8 ground rods with #6 bare copper as my GEC. Bonding with a bolted lug to the metal skin with a connection to the GEC. Neutrals and grounds will be separated in panel. I seem to be having a problem understanding the requirement for the equipotential plane. Since there is no metallic equipment that may become energized, is the E- plane still required? Or because I am bonding the skin of the building to the service, would the skin be considered metallic equipment that may become energized, thus requiring the E-plane? Since the metal corral fencing is not bolted together anywhere, do I need to bond each (any?) of these to the service? You can see a couple of pictures of the project at Photobucket . Thanks. Rick Miell
Here it's more a matter of knowing what was 'intended,' as opposed to what was 'written.' It can seem laughable, but the short form of the equipotential issue can be summed up with:
"Do I have a milking machine?"
That's pretty much what got the whole issue started. You didn't want your cow to step from an energized slab to a non-energized slab, or for your horse to nibble on wires without tripping the GFI.
In more technical terms, an 'equipotential plane' is one way to help 'lost' electricity get back to the panel, where it can trip the breaker. So, a key part of the issue is: where would the 'lost' electricity come from, and how would it get back to the panel?
Let's just, for the sake of argument, imagine that you had a powered conveyor bringing feed from outside, over that slab, and into that stable. In that situation, one might see the benefit to having the slab nicely bonded to the service, because a fault at the far end of the conveyor just might try to travel through the slab.
The use you propose does not require an equipotential plane.
As a design note, though, I'd suggest replacing that single light bulb with a pair of fluorescent fixtures. It'll make both the horse and the stablehand happier. You also might want to have an outside disconnect for the building (the Fire Dept. will love that!)
No, Yoopersup, I don't read it that way. 547 only requires it if there is electrical equipment and metal 'likely to become energized.' From his description, it sounds like this clearly agricultural site does not require an equipotential plane.
547,10(A) Where Required. 547.10(A)(1) Indoors. Equipotential planes shall be installed in confinement areas with concrete floors where metallic equipment is located that may become energised and is accessible to livestock.
Similar language applied in (2) for outdoor locations.
Absent the means of energizing the metal, you don't need an E.P.
What happens in the future is another thing entirely. Article 90 is pretty plain that the NEC is not intended to address future possibilities.
Looking at the pictures of the stable, I just don't see it being an issue.
The 2005 reads, in part, "containing metallic equipment that may become energized, and is accessible to livestock." That's where the E.P. is required.
So, we're still on the point of: is the metal present likely to become energized? With an all-PVC wiring method, and not accessible to the animals, I can't say it's "likely" to become energized. Nor can I stretch "may" to cover every possibility, however far-fetched. Were we to do that, there would be no need for the qualifier at all.
Nor do I consider fences and buildings to be "metallic equipment." Again, as with swimming pools, had the code panel meant 'all metal,' they would have said so. I don't see ANY equipment in the building under discussion - and I can't extend 'equipment' to cover a hend-held trimmer on an extension cord either.
You got a point I gotta admit. Be interesting to get others involved. Since metal siding & building metal would be required to be bonded . You could have a different potiental to ground between Fence, concrete, & metal building which in fact could get engerized. Wisconsin has a VERY Strick code on this for farms because farmers have lost so many animals there. Interesting sparing with you. Yoopersup