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
Industrail Control Panel bonding per 409.108
by sparkyinak
Yesterday at 03:17 PM
Calling all Non-US members!! (Non-US only)
by aussie240
12/07/16 02:39 AM
Photo Upload Tutorial
by DanK
12/06/16 11:35 PM
Sprinklered equipment 26-008
by bigpapa
12/02/16 04:24 PM
On Delay Relay with Auto Reset
by Potseal
12/01/16 09:59 AM
New in the Gallery:
12.5A through 0.75mm˛ flex (just out of curiosity)
Shout Box

Top Posters (30 Days)
gfretwell 13
HotLine1 9
sparkyinak 8
Texas_Ranger 8
Trumpy 6
Who's Online
0 registered (), 257 Guests and 5 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#96546 - 12/06/05 04:20 AM Grounding 12/2 and 14/2 cable in the same gang box
damoski Offline
Junior Member

Registered: 12/04/05
Posts: 2
Loc: Sterling, VA, USA
Prelude:
All ground conductors must be of sufficient size to trip the circuit breaker or fuse of the circuit that it protects, without overheating 15 amp circuit 15 amp wire, 20 amp circuit 20 amp wire. Refer to tables 250-94 and table 250-95, 1987 NEC (National Electrical Code).

Question:
I often combine two 14/2 cables from different circuits (15A fuses) in the same pigtail when wiring a three way switches. What are the implications of combining a 14/2 and 12/2 ground in the same pigtail?

Top
2014 / 2011 NEC & Related Books and Study Guides
#96547 - 12/06/05 06:08 AM Re: Grounding 12/2 and 14/2 cable in the same gang box
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Check out 250.148 for the need to tie all equipment grounding conducors together. And, if the connector used for this tieing together is suitable for mixed sizes, I don't see a problem.

Just as a side note- How does the older issue of the code fit into this issue?

[This message has been edited by George Little (edited 12-06-2005).]
_________________________
George Little

Top
#96548 - 12/06/05 02:19 PM Re: Grounding 12/2 and 14/2 cable in the same gang box
jwhite Offline
Member

Registered: 12/01/05
Posts: 67
Loc: Trenton, NC, USA
you are supposed to combine them all in the same pigtail. and the tail to the device should be the rating of the circuit to that device.

and the code has had several cycles since your version

Top
#96549 - 12/07/05 04:51 AM Re: Grounding 12/2 and 14/2 cable in the same gang box
damoski Offline
Junior Member

Registered: 12/04/05
Posts: 2
Loc: Sterling, VA, USA
Thanks very much for your response with regards to combining 14/2 and 12/2 ground in the same box. As for the reason I posted the code (granted it may be old: The ground conductor helps If there's an insulation or short to conduct the electricity away and possibly trip the breaker. In this case, a 14/2 is rated at 15A while a 12/2 is rated at 20A. In case of a short, the 14/2 doesn't seem to have the ca safely for a 20A circuit. May be I am reading too much into this, I need some coffee.

Thanks

Top
#96550 - 12/07/05 09:01 AM Re: Grounding 12/2 and 14/2 cable in the same gang box
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
Within a reasonable length, #14 will safely trip a 20a breaker with a bolted fault. The theoretical resistance necessary is <6 ohms. That is about 500 feet. Since breakers vary in their trip curves and other things come into play you could probably say 100' is a safer number. Certainly any short jumper would not be a problem. You are still going to bump up against the code tho.
_________________________
Greg Fretwell

Top
#96551 - 12/07/05 02:17 PM Re: Grounding 12/2 and 14/2 cable in the same gang box
Ryan_J Offline
Moderator

Registered: 08/19/03
Posts: 1355
Loc: West Jordan, Utah, USA
But when do you ever have a bolted fault?
_________________________
Ryan Jackson,
Salt Lake City

Top
#96552 - 12/07/05 03:27 PM Re: Grounding 12/2 and 14/2 cable in the same gang box
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
If it is an arcing fault, the minor difference in resistance between #12 and #14 is not going to make much difference.
_________________________
Greg Fretwell

Top
#96553 - 12/11/05 09:41 PM Re: Grounding 12/2 and 14/2 cable in the same gang box
Larry Fine Offline
Member

Registered: 02/18/05
Posts: 684
Loc: Richmond, VA
Plus, a #14 and a #12 paralleled have a lower combined resistance than either alone, so this only improves performance.
_________________________
Larry Fine
Fine Electric Co.
fineelectricco.com

Top
#96554 - 12/17/05 03:55 PM Re: Grounding 12/2 and 14/2 cable in the same gang box
Edward Offline
Member

Registered: 12/14/02
Posts: 309
Loc: California
Does the nec require this. Both 14 and 12 egc to be tied together if they are in the same box.

i have always kept them separate.

Edwrad
_________________________
Thanks
Edward

Top
#96555 - 12/17/05 04:09 PM Re: Grounding 12/2 and 14/2 cable in the same gang box
trekkie76 Offline
Member

Registered: 06/19/04
Posts: 219
Loc: baileyville, maine, usa
as george little said above, 250-148 requires that where the circuit conductors are spliced, terminated on equipment within or supported by the box, the grounding conductor with the circuit must be spliced together.

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