Using SO cord

[Hillbilly3]

Hey all new to the forum. Got a question about using SO cord. I'm helping my brother inlaw install a sub panel in his house. He wants to put in a 100 amp panel and it will be installed approx 25 ft from his main panel. We will be running the feeder wires through the ceiling to the new panel. Is it ok to use SO cord for the feeder wire? I have access to the wire so I thought I could help him keep his costs down but giving him some. Using/understanding the NEC code book is not my strong suit! Any help would be greatly appreciated.

 

[aandpdan]

Check with your local inspector. IMHO is no way. Do you really have #3 SO wire?
If you want to cut the costs down, use #1 AL wire. It's fine for a feeder and fairly inexpensive.

Some inspectors may allow #4 CU or #2 AL for your subpanel.

310.8 Locations.
(A) Dry Locations. Insulated conductors and cables used in dry locations shall be any of the types identified in this Code.
(B) Dry and Damp Locations. Insulated conductors and cables used in dry and damp locations shall be Types FEP,
FEPB, MTW, PFA, RHH, RHW, RHW-2, SA, THHN, THW, THW-2, THHW, THHW-2, THWN, THWN-2, TW, XHH, XHHW, XHHW-2, Z, or ZW.
(C) Wet Locations. Insulated conductors and cables used in wet locations shall be
(1) Moisture-impervious metal-sheathed;
(2) Types MTW, RHW, RHW-2, TW, THW, THW-2, THHW, THHW-2, THWN, THWN-2, XHHW, XHHW-2, ZW; or
(3) Of a type listed for use in wet locations.

It's a fixed subpanel, correct? If so, under section 400, type SO is rated for "pendant or portable." You have neither. In addition, you can't run that type of cord through a wall, or ceiling.

 

[Alchymist]

Some inspectors may allow #4 CU or #2 AL for your subpanel.

It's a fixed subpanel, correct? If so, under section 400, type SO is rated for "pendant or portable." You have neither. In addition, you can't run that type of cord through a wall, or ceiling.

#4 copper is rated 70 Amps in a NM cable, 85 in single conductor THWN.

#1 in NM or #2 in THWN for 100 amps.

 

[aandpdan]

Check table 310-15(b)(6)

#4 CU or #2 AL feeder or service 100 amp -- if they consider this a feeder.

 

[Alchymist]

Check table 310-15(b)(6)

#4 CU or #2 AL feeder or service 100 amp -- if they consider this a feeder.

Nope, not considered a feeder. Lot of people use 2-2-2-4 aluminum at 100 amps, some inspectors will call them on it and make them breaker it at 90, some won't. I have a sub -panel on #4 copper, max breaker is 85 amps.

 

[pattenp]

Check table 310-15(b)(6)

#4 CU or #2 AL feeder or service 100 amp -- if they consider this a feeder.

Also the feed to the sub-panel needs to be 4 conductor, not 3. The service/feeder section you quoted is for services/feeders that supply the main power to the dwelling.

 

[matt151617]

Also use a 70 amp breaker, it's much cheaper than a 90 or 100 amp. And I'm sure there won't be any problem with it tripping.

 

[frankush]

Type SO cable is considered a portable cord. Your panel is considered a permanent installation. It is not intended for that application.

 

[VHF]

#3 CU for 100A to subpanel. Three #3 CU THHN conductors in conduit plus ground, which can can be #8.

Even with the high price of copper it shouldn't be too bad for that short of run.

If conduit isn't workable, you will need a cable assembly that is legal for use indoors. Most service entrance type cable is not rated for use inside a building. Hopefully others can advise.

 

[pattenp]

#3 CU for 100A to subpanel. Three #3 CU THHN conductors in conduit plus ground, which can can be #8.

Even with the high price of copper it shouldn't be too bad for that short of run.

If conduit isn't workable, you will need a cable assembly that is legal for use indoors. Most service entrance type cable is not rated for use inside a building. Hopefully others can advise.

Your statement is not totally correct. Most power distribution cable is not rated for interior use. SE (Service Entrance) is allowed inside. That's why it's called entrance cable.

 

[Hillbilly3]

Thanks all for the quick replies. It will be a fixed panel. I didn't think the SO would fly. Guess it was wishful thinking since I had some and it seems to be more flexible and easier to work with. Thanks again

 

[Norcal]

See 400.8

400.8 Uses Not Permitted. Unless specifically permitted
in 400.7, flexible cords and cables shall not be used for the
following:
(1) As a substitute for the fixed wiring of a structure
(2) Where run through holes in walls, structural ceilings,
suspended ceilings, dropped ceilings, or floors
(3) Where run through doorways, windows, or similar
openings
(4) Where attached to building surfaces
Exception to (4): Flexible cord and cable shall be permitted
to be attached to building surfaces in accordance with the
provisions of 368.56(B)
(5) Where concealed by walls, floors, or ceilings or located
above suspended or dropped ceilings
(6) Where installed in raceways, except as otherwise permitted
in this Code
(7) Where subject to physical damage

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