URD/mobil-home cable in RMC?

[LarryFine]

I was called to a store with an open conductor in conduit between the POCO's under-sidewalk vault (containing nothing but splices) outside the mall and the inside-the-store meter and service.

FYI: Info related to me by phone: 208Y/120; between 100 and 200a; underground/underslab RMC, (will see tomorrow.) This mall was built around 1955, as far as I know, it's the original conduit.

I'll have to price replacing the conductors, I wanted to explore the options for conductor types. For example: quad URD (XPLE), says "direct burial or pulled in ducts"; and mobil-home feeder cable.

 

[mdshunk]

Most of the "mobile home feeder cable" I use also has NEC conductor type markings. I use it pretty regularly for feeders and such when I need those sizes, since it's convenient that it's "pre paralleled" and I'm not pulling separate conductors.

 

[LarryFine]

Most of the "mobile home feeder cable" I use also has NEC conductor type markings. I use it pretty regularly for feeders and such when I need those sizes, since it's convenient that it's "pre paralleled" and I'm not pulling separate conductors.

It's also a lot cheaper! For example:

For 100a:
2,2,2,4 al: $1.44/ft
#3 cu: $1.48/ft x 4

For 200a:
4/0,4/0,4/0,2/0 al: $3.44/ft
#3/0 cu: $3.47/ft x 4

Using copper would cost about 4x the cost of the aluminum. We need about 80 ft for the run.

I can save about $.50/ft by downsizing the neutral one size in copper. Big whoop.

My main concern is using the underground aluminum in the conduit. More profit.

 

[wireguru]

heres a brochure for URD, says for direct burial or installed in ducts. has ampacity table for both uses

http://www.prioritywire.com/s-20.pdf

 

[ptonsparky]

It is more difficult to pull into a conduit than individual conductors. We oversize the conduit or use long sweep 90s but that doesn't sound like an option here. Although 80' & 2 90s shouldn't be to tough for a young fellow.

 

[LarryFine]

Although 80' & 2 90s shouldn't be to tough for a young fellow.

Great, I'll hire one. :smile:

 

[peter d]

One poco in my area uses a utility version of the "mobile home cable" for all they UG laterals (triplex or quadplex 4/0 AL cable with yellow striped neutral.) I would assume that many other poco's do as well.

 

[mdshunk]

One poco in my area uses a utility version of the "mobile home cable" for all they UG laterals (triplex or quadplex 4/0 AL cable with yellow striped neutral.) I would assume that many other poco's do as well.

That's just straight "URD". The stuff the PoCo uses doesn't really have any NEC conductor type markings on it, so you can't really use it for an NEC install. I have bought URD at my supply houses that is marked with NEC conductor types, normally XHHW. The PoCo stuff is just normally marked XLPE, if it is marked at all, which doesn't really square with the NEC.

 

[LarryFine]

I think a call to the county AHJ office is in order. No point in proposing to use a non-compliant wire type.

Keep the opinions coming, please. (Right, like I have to solicit for that to happen! )

 

[mdshunk]

I think a call to the county AHJ office is in order. No point in proposing to use a non-compliant wire type.

Right, I wouldn't suggest you do that either. Just read the jacket, and don't worry about the inspector. If there is anything at all listed on the cable that squares with an NEC recognized wire type, you're free to use it.

I seriously doubt that you're going to find "mobile home feeder cable" with enough conductors in the right gauges for a 3-phase service anyhow.

 

[LarryFine]

Okay, a little more fun:

Can I use calculated load here, or must I go full size for the fuses? Or, another way, must I drop down to the next-lower standard fuse size? The main disco is a fusible switch with a set of 100a fuses, so it looks like I can't use #2 aluminum, because it's a business, unless I swap out the 100a fuses for a set of 90's. Am I correct?

The table to which WireGuru linked shows the "Dyke" cable style, which is what my local orange store shows on the WorksiteCD program at $1.44/ft, says it's good for 115a in duct. Is GRC = duct? It also says that's the 90-deg. rating. Interestingly, Table 310.16 shows that #1 al is required for that rating at 90 deg.

Referring to the afore-mentioned link mentioned before, which takes precedence, the manufacturer's specs or the NEC? The next size my orange store carries in URD is 4/0. Yecch! Is there anything useful for me here, or should I just go with copper? There's #2 in there now, but I could go with #3, but the savings is minimal.