Electricians here: can you tell me or lead me to the portion of the NEC which advises the following…
I’m feeding an office/shop w/ a 200A service from a freestanding service (meter and main disconnect) at a pole. It’s treated the same as a Mobile Home feed as far as I and the power co. understand it. In any case, I’m running 4/0 copper 4-wire through a buried conduit from the meter to the building and through the block foundation wall. The wire will be THHN, and will emerge in an enclosed crawlspace under the building where it will travel under the joists about 20 feet and up to a service panel (w/ a separate disconnect) inside the building. The question is this: Does the SE wire under the house have to be in a conduit?
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Since you didn't tell us which part of the country you're in I suggest a conversation with your local AHJ. Locally this would need to be in sch. 80 pvc and treated like a sub-panel complete with regrounding the load center, so give your inspector a call.
Unfortunately, the part of the country I'm in has employed lazy and ignorant inspectors who either won't follow the code, or don't know it (they have admitted both to me on separate occasions). If I was real lucky, the advice I received would be wrong, I'd do it their way, and later, on inspection, be told it was "wrong" and get to re-do it. Which is what I'm trying to avoid. Having to go back and re-route a SE wire through a conduit after-the-fact kinda sucks. We do use the NEC here in FL, and the building codes follow it. So that's why I was asking...Anyone know what the NEC specifies, if anything?
The fact that it is a feeder does not matter in this case as the wiring is protected by the overload (breakers or fues) at the meter/disconnect.
But THNN can not be run except in conduit or race way.
So you either need use conduct inside the building or transistion to a cable system such as SE cable.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Good catch Bill, I misread that as SE cable, which in our area still needs the sch. 80 [they disaalow emt or sch. 40].
I recently looked at a pool heater that had one #2 thhn stapled to the tails of the rafters running one direction and the other feeder was routed through the crawl space, just two seperate conductors going two different directions, no bond, ending at a disconnect. It's a hard thing to tell the customer that you have to start over from the beginning and make it right. " But it's worked for ten years thata way..."
Thanks Bill...The Elec.Co. engineer (who installed the pole and ran the drop from a new transformer) told me THHN could be direct buried, so I guess I assumed that I could then forgo a conduit in a crawlspace (why aren't conduits required in an attic space?). Anywho, I'll use a conduit. But if I transitioned to a a normal sheathed SE cable at the entry point, what would be the preferred method? Splice right at the 2-1/2" conduit body (elbow) which penetrates the house wall? Can this be used as a 'j-box' for SE cable?
There is a direct burial single wire. I was surprised when I saw that. And that wire basically has a sheathing.But it ain't THNN. In fact THNN is not approved for inground conduit. But THWN is. And much (most, all)THNN is also dual marked THWN.In side the house everything needs to be in races ways or conduit or an apropriate cable (NM, SE, AC, etc)Two reasons. One is to make sure that all of the conductors stay together. The other is for basic protection. How much protection needed depends on the application.I have not used that size wire or conduit body needed for it. But I would be real surprised that you have enough space. Some conduit bodies are makred with a volumn rating and can be used for splicing, if it is within the size requirements..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Edited 3/31/2008 6:33 pm by BillHartmann