Electrical question.....

tanstaafl72555

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I have a run of 6/2 rf cable that I want to use to do a 30amp service to a utility building (not yet erected). I already am running a 10/3 section to another subpanel to an existing building. I know that you need a four stranded wire to prevent an overload on the ground/common, so you need a separate ground (all panels nowadays are for four stranded wire).

Here is the question: Before 1974, you COULD run standard 3 strand wire to a panel, so I am a bit skeptical about the demands in the first place.... , but suppose you ran the 6/2 and then used a standard copper grounding wire to go from ground to ground, and then put in a grounding stake at the termination point. What would be the safety issues with that?

Please don't quote the code to me. I know what it says here in NC. I also know that in other states, this practice (actually running three strands to a sub) is permissible.

What I want to know is from the perspective of SAFETY, it seems to me that an overload on the common (what you would have with 6/2 alone... without the extra ground wire), would trip the breaker on a 30 amp circuit ANYWAY, and adding a ground is just insurance. Any comments? The utility building is going to be a butler bldg (all metal) so I am not worried about insurance denying a claim. I *AM* wondering if there are inherent safety factors that I have missed.

Thanks in advance,

Tans the Chess Pigeon
 
Any electricians in here want to comment? The electrician I normally lean on to help me happens to be the mayor of our town and I don't want to ask questions about work not done to code ;) .
 
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I recognized "30 amp" because that's what I plug my travel trailer into. Beyond that, you were speaking a language unknown to me. :D

Best of luck with your endeavor.
 
it seems to me that an overload on the common... would trip the breaker on a 30 amp circuit ANYWAY


If you're referring to a 2-pole 220 volt breaker, no. A standard breaker will only trip when it senses an over-current condition on one of the hot legs. From the perspective of the breaker, so long as current through the hot legs doesn't exceed the trip point, everything is working fine.

GFCI and AFCI breakers are another story and will trip for over current on the hot legs or for any current on the neutral/common leg.
 
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If you're referring to a 2-pole 220 volt breaker, no. A standard breaker will only trip when it senses an over-current condition on one of the hot legs. From the perspective of the breaker, so long as current through the hot legs doesn't exceed the trip point, everything is working fine.

GFCI and AFCI breakers are another story and will trip for over current on the hot legs or for any current on the neutral/common leg.

Thank you. I am assuming then that the only reason for a 4 wired connection is the possible overload on the common if we have a ground and common using the same wire. In that case, why would a standard uninsulated wire for a ground NOT be a sufficient safety precaution to prevent an overload on that part of the circuit?

DISCLAIMER: I am admittedly, a total idiot here. Please feel free to be a contemptuous and dismissive as one would need to be if you sense belligerence in my question :) (there is none, but I have been told........). I just want to understand and this is not my forte.
 
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