How to A/B Test Power Cables & Interconnects?

If you have a modern breaker panel in the U.S., all of your grounds are joined at a single bus bar in the panel, and then go to ground. If you have dedicated circuit(s) going directly to the panel, you shouldn't have any metal electric boxes for outlets. Or anything else. They're obsolete, and a liability in a modern electrical layout, in all but a few exceptions.

By code, they (grounds) have to be all connected at the panel to a single bus-bar do they not?

Perhaps obsolete, and I wonder if regional, but I am still seeing more metal boxes even in new construction, in north east U.S. and Canada, but pretty much all plastic with integrated vapor barrier for the exterior. Are we talking the same thing? i.e. ... https://www.homedepot.com/p/2-Gang-Drawn-Device-Switch-Box-with-Bracket-685SP/100154820

Sounds like you know this well. I would be interested in your insights ... and how it relates to mechanical as per the next paragraph.

While metal boxes have higher potential for "liability", if they are improperly grounded and a live wire touches the box, and a person touched a screw that attached to the outlet cover that attached to the box, then yes they could get a shock. (Or you cut the romex on the sharp metal). On the other hand, with people hanging literally pounds of audiophile AC cables off them, and multiples at that, the significantly higher rigidity of metal could balance out any benefits of plastic.

That said, for the DIYer, plastic can be safer (and easier), and since the gauge used was 10, it should be easy to just run each ground to the separate receptacles (in the same j-box), and then run a ground wire between each receptacle so the grounds are at the same potential.

robert, first, I’m not an electrician, so take anything I say with a grain of salt. That being said, I have been in residential construction for 30 years. I’m in the Pacific NW. I’ve never seen an electrician here use a metal box in a home without good reason. Something heavy, like a ceiling fan, or remodel work in an older home. I wouldn’t think audio AC cables would rise to that level, given a quality box like a Pass & Seymour, etc.I wouldn’t run a ground like you describe. An electrician may or may not, I’m not sure. Generally, from my limited understanding, it’s not advisable to just bond grounds together at random. I’d have two separate circuits, or only one.

P.S. My panel has two bars, one on the right, one on the left. Grounds and neutrals connected to the nearest spot. Both bars are connected behind the main breaker I believe, and then to the ground lug.

I am not an electrician either, though was once fairly handy with the electrical code, but that was a while ago. Just went down to my panel, as expected, I have a dual single pole breaker that both trip at the same time (not a common 2-pole), however, perusing HD website and I can't find this style any more, so that tells me that maybe they don't make them any more?

Perusing the web, it does not appear that doing this is verboten, but, like my installation, you would (for residential) need a breaker that disables the circuit at the same time. That could be tough with a breaker panel, easy with a ganged breaker in a box. 

The easiest thing, that would not confuse inspectors, would be to have two outlets close together and just tie a ground between the two.


builder3203 posts10-22-2019 6:26pmrobert, first, I’m not an electrician, so take anything I say with a grain of salt. That being said, I have been in residential construction for 30 years. I’m in the Pacific NW. I’ve never seen an electrician here use a metal box in a home without good reason. Something heavy, like a ceiling fan, or remodel work in an older home. I wouldn’t think audio AC cables would rise to that level, given a quality box like a Pass & Seymour, etc.I wouldn’t run a ground like you describe. An electrician may or may not, I’m not sure. Generally, from my limited understanding, it’s not advisable to just bond grounds together at random. I’d have two separate circuits, or only one. 

Why not just have one circuit? There’s no load to speak of. A single run of 12 wire and whatever outlets and box you care to use should be more than adequate.
On a separate note (and run this by a real electrician), I’m wondering if there’s any reason you’d be prohibited from having the two separate circuits, but only use one of the grounds for both. Leave the second ground unused in the back of the box. May be reasonable, may not be, talk to a pro.