ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by gfretwell - 03/28/24 12:43 AM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
1 members (CoolWill), 250 guests, and 13 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
#10555 06/15/02 01:53 AM
Joined: May 2002
Posts: 68
E
Eandrew Offline OP
Member
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.

#10556 06/15/02 08:12 AM
Joined: Oct 2000
Posts: 2,749
Member
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
#10557 06/15/02 12:34 PM
Joined: Jun 2001
Posts: 196
C
Member
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.


Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5