Grounding Metal Outlet Boxes and Isolated Ground Receptacles

Main issue is I do not want to create an electric hazard (pretty sure my electrician is very capable) and I do not want to create a bunch of ground loop issues!

From the description of the wiring materials and wiring methods used in your posts everything meets or exceeds electrical safety code. At least NEC. I would imagine your electrician followed any local electrical codes that differed from NEC.

As for any ground loop problems, just my opinion, your branch circuits runs are too short to cause any ground loops. If they were long, say 60ft to a 100ft, the 6-3 with ground may have been a problem as I described in an earlier post. Especially paralleling the bare equipment ground wire with one of 3 insulated conductors of the cable.

I wouldn’t be surprised though if the electrician doesn’t rework the equipment ground wiring in the six wall rough-in outlet boxes after you tell him the 6 duplex receptacles are not IG grounding type duplex receptacles. He has to hang his name and reputation on the job when he’s done.

As far as the way I would do it now, knowing the duplex receptacles are not IG, I would cap off the insulated wire in the box and just leave it as a spare unused wire. I would pigtail the bare equipment ground with two pigtails. One to bond the metal box and the other to connect to the ground terminal on the duplex receptacle.

(Just going from memory the construction of 6-3 with ground NM-B cable (Romex), the bare ground wire is in the middle of the three twisted insulated wires. For me anyway, that lessens any chance of an induced voltage transfer from the hot and neutral current carrying conductors onto the equipment ground wire.)

As for what to do with the spare capped off wire of the 6-3 with ground Romex at the electrical panel end? Normally it would be capped off and left laying in the bottom of the panel for future....... But in this instance it is part of a cable assembly that will be feeding an audio system. An audio system where the user has spent big bucks in hopes of getting the lowest noise floor possible. I would wonder if the floating insulated wire might act as an antenna and pick up air born RFI. I would probably connect the end at the panel to the ground bar. Nothing wrong with that as far as a code issue. Ask your electrician if he has a problem with it.

It would be nice to hear from Al, (almarg), what he thinks. Would he connect the end of the spare insulated wire at the electrical panel to the ground bar, or leave it floating above ground?

Jim

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One option we are looking at is to pull out the metal boxes, put in a high quality plastic or fiberglass box and elimintate any ground to the box.

I don’t think the electrician will find a plastic or fiber receptacle outlet rough-in box big enough for 6-3 with ground that will meet NEC for the conductor fill requirements. (2014 NEC 314.16) That’s why, I believe, the electrician used a steel square box with a single gang raised device cover. I personally would leave what you have now. If the receptacle supporting back strap was made of steel then you might hear a difference in sound. The supporting back strap on the Furutech is not made of ferrous steel. What type of duplex cover plate are you going to use? THAT can change the sound of your audio system!