The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Forum Software Upgrade coming soon...
by Ruben Rocha
01/18/17 07:05 PM
ESA Arc flash course
by frank
01/18/17 04:25 PM
Re: Fabricating Guards out of Lexan?
by frank
01/17/17 04:11 PM
Would ELV branch circuits be a good idea?
by gfretwell
01/17/17 01:26 PM
Why cables look like they do
by Texas_Ranger
01/17/17 12:33 PM
New in the Gallery:
Desk-mounted "power-board"
Top Posters (30 Days)
Webmaster 26
HotLine1 21
Ruben Rocha 14
Trumpy 12
ghost307 12
Who's Online
2 registered (Webmaster, Ruben Rocha), 0 Guests and 187 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#10555 - 06/14/02 10:53 PM concentric vs ecentric
Eandrew Offline
Member

Registered: 05/24/02
Posts: 69
Loc: seattle, wa, usa
I need help in determining the difference (with respect to running an jumper )of concentric vs ecentric knock out. which one requires an additional bonding jumper. which knock does not provide an ground path.

I saw NEC refers to this in services, but what about disconnects in general.

Top
Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#10556 - 06/15/02 05:12 AM Re: concentric vs ecentric
Joe Tedesco Offline
Member

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA
See Section 250.97 in the 2002 NEC where the same rule can be found concerning the ko's you described.
_________________________
Joe Tedesco, NEC Consultant

Top
#10557 - 06/15/02 09:34 AM Re: concentric vs ecentric
Cindy Offline
Member

Registered: 06/23/01
Posts: 196
Loc: PDX, OR, US
this is what i understand to be true but maybe someone else can verify this.....
short answer, theres no difference, neither k/o has likely been certified in equipment to carry currents.
250.92 says to bond around both concentric and eccentric knockouts with bonding jumpers at "services" regardless of voltage, then 250.97 says for over 250 volts to ground, metal raceways and cables with metal sheaths that contain any conductor "other than service" conductors have to be bonded same as in 250.92, except for option(1) because that would be bonding equipment to the g.c. on the services load side downstream.
i've used a listed 4 square box with only one eccentric k/o that doesn't need to be bonded around because the locknuts can make good enough contact outside the eccentric ring, but have to be sure its listed for that.
my understanding is that like reducing washers, the k/o's in gutters and panels are never acceptable to carry any currents so they should always be bonded around with bushings and jumpers, except for the type i mentioned above.

Top


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals