Can conduit rest on floor of crawl space?
I will be running 4/0 XHHW-2 wires from a metered pedestal with a main breaker through 2″ PVC conduit under my footing and across a crawl space for roughly 30′ and then up into my main breaker panel in the house. (I’m building the house on a site that had a manufactured home many years ago.) The conduit will be continuous for the entire run. I’ve spent much of the day trying to learn whether the conduit can rest on the floor of the crawl space or hang below the 2″ polyiso that insulates the undersides of the floor joists. The most relevant part of the 2012 IRC, the governing code here, is TABLE E3803.1: MINIMUM COVER REQUIREMENTS, BURIAL IN INCHES, which says 12 inches under 2 inches of concrete, 0 inches “Under a building,” 4 inches “Under minimum of 4-inch thick concrete exterior slab with no vehicular traffic,” or 18 inches otherwise. Digging or pouring concrete in the crawl space would be difficult, but these requirements, other than “Under a building” seem to be intended mostly if not entirely for outdoors. It seems logical that a crawl space would be “Under a building,” even though it’s part of the building, because in what other situation would a conduit rest upon the ground underneath a building (and not be covered by a slab)? Is conduit allowed to rest upon the ground in a crawl space? If not, can I hang it below the polyiso, which would be the second easiest choice?
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A crawl space is inside, not under, the building. It needs to be secured and protected from damage -- it needs to be screwed to something, either a wall or the underside of the joists. I would use 3" screws and go through the foam to attach clamps to the joists. If the position of the joists doesn't work out, screw a piece of 1x3 or plywood under the foam and screw into that.
Oh, and inside a building you don't need conduit, you can just run Romex. Local jurisdictions vary about how well-protected the Romex needs to be, whether it can be stapled to the bottom of the joists or whether it has to go through drilled holes.
Is the insulation already in? I'd do the wiring before insulation.
Thank you, DC. Yes, the crawl space is part of the building, but in what other setting could conduit lay on the ground with 0" burial "Under a building"? These are the main feeder wires for the entire house's power, much bigger than Romex and much too big to run through holes in the joists.
Under a concrete slab.
Under a slab would be under at least 4" of concrete, which is another of the allowable options, so why would the code list 0" "Under a building" separately?
Note footnote for table :
“1. Cover is defined as the shortest distance in mm (in.) measured between a point on the top surface of any direct-buried conductor, cable, conduit, or other raceway and the top surface of finished grade, concrete, or similar cover.“
I think I agree that this is an allowable method of install, though you might consider fastening to joist bottom to protect it from damage. 2” conduit must be fastened 5’ intervals if I’m not mistaken
Lying on the floor is not "direct-buried."
The standards are somewhat subjective, but here conduit just lying on the floor wouldn't pass the standards for being secured and protected. It would probably also fail for general workmanship.
This seems like a gut feeling reply and not a reading of the code. That table is fairly explicit in saying that this is allowed and doesn’t particularly seem subjective. What part of the table, footnotes, or following code snippets seems subjective?
There is clarity of the requirements for slab cover, when dealing with rocky ground, when direct burial is used (must be in raceway under building).
Also how else do you interpret 0” of cover if not no cover, or in other words laying on the ground.
Thank you, freyr_design. Given the footnote you cited, it seems possible that 2" conduit would be considered "secured" if it laid in a groove in the dirt so that its top surface was not buried, but enough of it, say half of its diameter, was surrounded by dirt that it couldn't move. Enough of it being above the dirt also seems important so that one would know it's there and therefore not damage it. Plumbing waste pipes commonly lay on the dirt in a crawl space and are not considered overly at risk of damage.
By "Romex" I mean Service Entrance Cable. In 4/0 it's about 1.25" diameter, you can run it through framing members 2x6 or bigger.
If the foam is already in, run a piece of treated 1x3 across the ceiling of the crawl space and staple up the SE cable.
Since it is from a fused feed, it doesn't need to be buried. You can run it on the ground if secured but I think it will be in the way if you need to work down there. I would attach to the ceiling.
Thank you, Akos.
How much protection is required for the cable after the meter can be a very local thing.
I am not sure I would consider the service entrance cable fused. Yes, there is a 600-amp fuse on the pole but I don’t want to be near the short that would blow that fuse.
Type SE cable secured to the joists would be allowed in some locations, conduit is a safer option for a little more money.
Keep the floor as clear as possible you don’t want workers crawling over this conduit
Consider if you need to ask such basic questions is it a good idea to be installing the service entrance wiring? You get this wrong and the guy installing the meter could be killed. Generally, only licensed people are allow to do this work for the workers protection.
Walta
The feeder is fused by the breaker in the pedestal just outside the house, which already has a meter installed. In much of the US, one doesn't need a license to install a feeder. It gets inspected before anyone else works on the system. A question about a section of code that is less than obvious about a crawl space, specifically, may be less "basic" than you believe.
This is really a question for your inspector. The code says wiring can't be subject to damage, at the end of the day it's his judgment as to whether it's protected enough.
Incidentally, no way you could run an unprotected drainpipe across the floor of a crawlspace here.
Run it in tech cable and strap it to the floor joist, or go through the joists if possible. Tech cable has a armoured sheathing so it is considered protected. I think that what I call tech cable may be what others are calling service entrance cable. Run it in aluminum rather than copper, it’s slightly larger size but much much cheaper.
You may also need a disconnect within 10’ of entering the house. You usually cannot enter the house and then run an additional 30’. Ask your local Authority Having Jurisdiction about that one..
Thank you. The pedestal with a main breaker is less than 10' from the house.