2

Improving unfinished basement in 7 year old log home to have a small shop and a mancave

Installing sub panel 40 wire feet from main panel mainly because i don't want to home-run all my circuits to the main panel. Shop wiring going to main....only man cave (240 volt 3000 watts of heat and lighting/tv) powered from new sub panel

125 amp Eaton main lug sub panel and a Siemens main panel. Put 50 amp breaker in main, and ran 6/3 with bare ground to sub panel. Ground appears to a 10 AWG.

Neutral bar was strapped to ground bar in sub panel from factory so I removed the strap. Both ground bar and neutral bar are isolated from case via large plastic standoffs, so, i used the same strap to connect to floating ground bar to the sub panel enclosure. So, the neutral in the sub panel is only grounded back at the main panel.

THE QUESTION: Is the #10 AWG sufficient to ground the sub-panel to the ground bar in the main panel?

I am getting confusing info from other threads on this site and other web sites (probably my own reading comprehension issues).

The ground will never carry "neutral" current given the neutral is not connected to ground in the sub panel. I have seen at least two threads that claim that the ground must match the size of the two hots (6 AWG).

Improve this question
3
  • 1
    "but in no case shall [the ground] be required to be larger than the circuit conductors supplying the equipment." Typically if buying a single cable to run your feeder, as would be easy, you'd just buy a #6 and then you'd have a #6 ground in it as well - which wouldn't hurt anything, it might just cost a little more than having them separate and in conduit.
    – TFK
    Jan 30, 2016 at 15:59
  • 1
    @TFK OP said they "ran 6/3 with bare ground", so it sounds like they did buy a cable. And the cable had a #10 grounding conductor. Which according to this document, is what I'd expect.
    – Tester101
    Jan 30, 2016 at 16:34
  • @Tester101 Whoops. Don't know what I was thinking.
    – TFK
    Jan 30, 2016 at 18:45

1 Answer 1

Reset to default
8

According to Table 250.122 of the National Electrical Code, a 10 AWG copper conductor is fine as an equipment grounding conductor for circuits with up to 60 ampere protection.

National Electrical Code 2014

Chapter 2 Wiring and Protection

Article 250 Grounding and Bonding

250.122 Size of Equipment Grounding Conductors.

(A) General. Copper, aluminum, or copper-clad aluminum equipment grounding conductors of the wire type shall not be smaller than shown in Table 250.122, but in no case shall they be required to be larger than the circuit conductors supplying the equipment. Where a cable tray, a raceway, or a cable armor or sheath is used as the equipment grounding conductor, as provided in 250.118 and 250.134(A), it shall comply with 250.4(A)(5) or (B)(4). Equipment grounding conductors shall be permitted to be sectioned within a multiconductor cable, provided the combined circular mil area complies with Table 250.122.

table 250.122

Improve this answer
4
  • so, one of my circuits on the sub panel uses #10 AWG to supply 3000 Watts 240 V heaters. the other 4 circuits are all #12 AWG. Therefore, if i read the code correctly, none of the "circuit conductors" (in the sub panel) exceeds the #10 AWG ground wire between the main panel and the sub panel.....so, i am OK and code compliant it appears. Sound correct? Sorry if i seem dense......i want to be 10000% sure. THANKS !!!!!
    – Jhauhn
    Jan 30, 2016 at 16:34
  • 3
    @Jhauhn It doesn't matter what's in the panel. Table 250.122 is based on the overcurrent device that is in the main panel, which is protecting the circuit that feeds the second panel. You fed the second panel through a 50 ampere breaker, so #10 copper is fine.
    – Tester101
    Jan 30, 2016 at 16:36
  • 1
    To use a tree analogy. The main panel is part of the trunk. The second panel is a limb. And any circuit that comes out of the second panel, is a branch. In this case, the code is only concerned with the limb. It doesn't care about the branches coming off the limb. Though it shouldn't matter anyway, since none of the branches should larger than the limb.
    – Tester101
    Jan 30, 2016 at 16:49
  • Thanks very much folks. Yes, I had already bought and ran Romex with three #6 AWG conductors and a #10 AWG bare ground. Reading stuff on web to assure I was doing the absolute right thing with the ground and the neutral bus bars in sub panel, I started seeing the confusing info on the required size of the ground, between the main panel and the sub panel..... Now, I know the#10 AWG is OK. The definition of "circuit conductors supplying the equipment" may still wonder....but now I understand that that means the conductors to the sub panel, and sub panel is the "equipment". Thanks.
    – Jhauhn
    Jan 30, 2016 at 21:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.