Subpanel wiring question

[Bart]

Installing sub panel.

Can I use #4 USE conductor indoors? How about if it's in conduit? (3-#4 conductors+ground)

thanks.

[Paul Franklin]

Yes, per the NEC. Your local codes may vary. It doesn't need to be in conduit unless it's in a location where it might be easily damaged.

Paul

[Tom Horne]

Type USE cable may not be used indoors. The use of three conductor type SE cable as a feeder carrying 120/240 volt circuits violates the requirement that conductors be insulated. If the conductors in question were type SE then they could be installed indoors. If the cable was four conductor type SE cable then you could use it for a feeder.

-- Tom

310.2 Conductors. (A) Insulated. Conductors shall be insulated. Exception: Where covered or bare conductors are specifically permitted elsewhere in this Code. [There is no exception in the US NEC that would permit the grounded current carrying conductor of a feeder to be uninsulated when installed indoors.]

338.10 Uses Permitted. (A) Service-Entrance Conductors. Service-entrance cable used as service-entrance conductors shall be installed as required by Article 230. Type USE used for service laterals shall be permitted to emerge from the ground outside at terminations in meter bases or other enclosures where protected in accordance with 300.5(D). (B) Branch Circuits or Feeders. (4) Installation Methods for Branch Circuits and Feeders. (a) Interior Installations. In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Parts I and II of Article

334, excluding 334.80. FPN:See 310.10 for temperature limitation of conductors. (b) Exterior Installations. In addition to the provisions of this article, service-entrance cable used for feeders or branch circuits, where installed as exterior wiring, shall be installed as required by Article 225. The cable shall be supported in accordance with 334.30, unless used as messenger-supported wiring as allowed by Article 396. Type USE cable shall be installed outside in accordance with the provisions of Article 340. Type USE shall be permitted to be terminated in enclosures at an indoor location where Type USE cable emerges from the ground. The length of the cable extending indoors to the first termination box shall not exceed 1.8 m (6 ft). Where Type USE cable emerges from the ground at terminations, it shall be protected in accordance with 300.5(D). Multiconductor service-entrance cable shall be permitted to be installed as messenger-supported wiring in accordance with Articles 225 and 396.

[Tom Horne]

Paul Type USE multiconductor cable is only suitable for use underground. The single conductor variety could only be used in conduit.

-- Tom

[Paul Franklin]

OP said 3 conductors plus ground.

338.10B4a allows interior use.

If OP had said 2 conductor plus ground I'd agree with you.

Paul

[Tom Horne]

Paul The original poster also said that type USE cable is what he has. Type USE cannot be installed indoors. 338.10 (B) (4) (a) only covers type SE cable. Type USE cable is under 338.10 (B) (4) (b) which is titled "Exterior Installations." That section specifically limits the length of type USE that extends indoors to six feet. What the OP probably has is type SE because type USE is hard to find in 4 conductor.

-- Tom

338.10 Uses Permitted. (B) Branch Circuits or Feeders. (4) Installation Methods for Branch Circuits and Feeders. (a) Interior Installations. In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Parts I and II of Article 334, excluding 334.80. FPN:See 310.10 for temperature limitation of conductors. (b) Exterior Installations. In addition to the provisions of this article, service-entrance cable used for feeders or branch circuits, where installed as exterior wiring, shall be installed as required by Article 225. The cable shall be supported in accordance with 334.30, unless used as messenger-supported wiring as allowed by Article 396. Type USE cable shall be installed outside in accordance with the provisions of Article 340. Type USE shall be permitted to be terminated in enclosures at an indoor location where Type USE cable emerges from the ground. The length of the cable extending indoors to the first termination box shall not exceed 1.8 m (6 ft). Where Type USE cable emerges from the ground at terminations, it shall be protected in accordance with 300.5(D). Multiconductor service-entrance cable shall be permitted to be installed as messenger-supported wiring in accordance with Articles 225 and 396.

[Bart]

One of my suppliers has #4USE on sale for $.27/ft which is a fairly good price. But I can't find anything in my NEC about indoor use. My code book is 1999 so that doesn't help too much either. It doesn't have some of the articles you mentioned.

Anyway, I found some #4THHN.... OK indoor and can use underground if it's in conduit. I was hoping to run service to my new unattached garage off my sub panel. My subpanel would be about 10ft from a outside wall though. If I trenched from my house main service panel I would have to cross my service entrance cables TWICE. That would not be fun. I'll have to run my plan by the elec. inspector.