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Grounding 12/2 and 14/2 cable in the same gang box #96546 12/06/05 08:20 AM
Joined: Dec 2005
Posts: 2
D
damoski Offline OP
Junior Member
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?

2017 / 2014 NEC & Related Books and Study Guides
Re: Grounding 12/2 and 14/2 cable in the same gang box #96547 12/06/05 10:08 AM
Joined: Jan 2004
Posts: 1,507
G
George Little Offline
Member
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
Re: Grounding 12/2 and 14/2 cable in the same gang box #96548 12/06/05 06:19 PM
Joined: Dec 2005
Posts: 64
J
jwhite Offline
Member
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

Re: Grounding 12/2 and 14/2 cable in the same gang box #96549 12/07/05 08:51 AM
Joined: Dec 2005
Posts: 2
D
damoski Offline OP
Junior Member
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

Re: Grounding 12/2 and 14/2 cable in the same gang box #96550 12/07/05 01:01 PM
Joined: Jul 2004
Posts: 9,623
G
gfretwell Offline
Member
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
Re: Grounding 12/2 and 14/2 cable in the same gang box #96551 12/07/05 06:17 PM
Joined: Aug 2003
Posts: 1,374
R
Ryan_J Offline
Moderator
But when do you ever have a bolted fault?


Ryan Jackson,
Salt Lake City
Re: Grounding 12/2 and 14/2 cable in the same gang box #96552 12/07/05 07:27 PM
Joined: Jul 2004
Posts: 9,623
G
gfretwell Offline
Member
If it is an arcing fault, the minor difference in resistance between #12 and #14 is not going to make much difference.


Greg Fretwell
Re: Grounding 12/2 and 14/2 cable in the same gang box #96553 12/12/05 01:41 AM
Joined: Feb 2005
Posts: 693
L
Larry Fine Offline
Member
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
Re: Grounding 12/2 and 14/2 cable in the same gang box #96554 12/17/05 07:55 PM
Joined: Dec 2002
Posts: 308
E
Edward Offline
Member
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
Re: Grounding 12/2 and 14/2 cable in the same gang box #96555 12/17/05 08:09 PM
Joined: Jun 2004
Posts: 220
T
trekkie76 Offline
Member
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.


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