un-insulated grounded conductor

[ryan_618]

I did an inspection the other day for a detatched garage with a panelboard. The feeder circuit was a three wire cable consisting of two insulated conductors (ungrounded) and one bare (grounded). I cited article 310.2(A), but I wonder if that was the best article to cite. I couldn't find anything under article 200. Anybody have a better reference or is this the proper code? Thanks.

 

[bennie]

Re: un-insulated grounded conductor

Is this feeder in conduit, direct burial, or overhead span?

 

[ryan_618]

Re: un-insulated grounded conductor

Conduit, underground

 

[vanwalker]

Re: un-insulated grounded conductor

what type of cable is being used?

 

[ryan_618]

Re: un-insulated grounded conductor

SE

 

[websparky]

Re: un-insulated grounded conductor

Service-Entrance Cable.
338.10 (B) Branch Circuits or Feeders.
Uses Permitted.
(2) Grounded Conductor Not Insulated. Type SE service-entrance cable shall be permitted for use where the insulated conductors are used for circuit wiring and the uninsulated conductor is used only for equipment grounding purposes.

 

[ryan_618]

Re: un-insulated grounded conductor

Circuit conductors...branch OR feeder? OOPS!!! I think I may have blown it on this one!!!

 

[txsparky]

Re: un-insulated grounded conductor

(2) Grounded Conductor Not Insulated. Type SE service-entrance cable shall be permitted for use where the insulated conductors are used for circuit wiring and the uninsulated conductor is used only for equipment grounding purposes

If the bare conductor is being used for the Grounded Conductor then this is a violation. If the bare conductor is only being used for equipment grounds, then there is no violation.

 

[vanwalker]

Re: un-insulated grounded conductor

Q: type of cable question?
A: SE
problem? I need another letter for cable type, not trying to be picky ?

DON'T READ THE PRO---- am i reading this incorrectly? type SE with a bare wire
underground ? who cares about the support.

PLEASE-- continue to disregard the question.

[ July 31, 2003, 10:57 AM: Message edited by: vanwalker ]

 

[kevin]

Re: un-insulated grounded conductor

Since when can Type SE cable be installed in a raceway? It needs to be supported every 4 1/2 feet
in accordance with 338.10(B)(4)(a) and (b); the actual text comes from 334.30. In addition, the heat dissipating properties of the cable are severely compromised when installed in a raceway. Keep in mind that the cable is designed and tested in free air- not embedded in cellulose insulation or installed in a raceway.

 

[bennie]

Re: un-insulated grounded conductor

Kevin: What is the section that forbids SE cable from being in conduit? Does a cable heat more in a conduit than in free air?

 

[kevin]

Re: un-insulated grounded conductor

Bennie: The articles previously cited require that SE cable be installed in accordance with 338.30 which in turn requires that cable be "secured" every 4 1/2 feet maximum. This would rule out the installation of SE cable in a raceway longer than 4 1/2 feet, unless one could come up with a device that would secure the cable inside the raceway. On another note, UL does not list any SE cable for installation anywhere other than aboveground: Service Cable (TXKT) and Service Entrance Cable (TYLZ). This fact does not address your question, but does address the propriety of the installation described in the initial post. Personally, however, I would be mostly concerned about possible cable failure from excessive temperatures. As you are aware, the ampacity of conductors and cables is higher in free air than it is when installed in a raceway or embedded in insulation. I will attempt to contact a cable manufacturer, such as Southwire or Alcan, to learn their position on this matter. I will post that info when I have it. Thanks for your thoughtful inquiries.

 

[bennie]

Re: un-insulated grounded conductor

Kevin: What is the definition of secured?

 

[kevin]

Re: un-insulated grounded conductor

Bennie: Per www.dictionary.com, when "secure" is used as a transitive verb, its second definition is "To make firm or tight; fasten".
UL says that they do not test SE cable in a raceway. The engineer I spoke to guessed that the reduction in ampacity would not be considerable.
Alcan said that they have not tested either, but that they would not be very concerned about derating a cable in a raceway.

 

[david]

Re: un-insulated grounded conductor

334.15 Exposed Work.
In exposed work, except as provided in 300.11(A), the cable shall be installed as specified in 334.15(A) through (C).
B) Protection from Physical Damage. The cable shall be protected from physical damage where necessary by conduit, ?????...

Being that the NEC specifically states NM cable can be installed in conduit. I don?t think the securing argument holds water.

[ July 31, 2003, 02:04 AM: Message edited by: david ]

 

[hillbilly]

Re: un-insulated grounded conductor

The way I understand it is: 2 conductor SE cable with bare ground can be used as a feeder to other buildings on the same premises only if the main disconnect for the other building is located at this building. The neutral and grounding terminals should be bonded and a ground rod installed and bonded at the breaker panel. The SE cable should have a outer covering enclosing all the conductors. I think burial in conduit is OK.

If the service disconnect for the other building is remote (located at the main building) then 4 conductor cable should be used and the grounds and neutral seperated in the other building panel.