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Grounding Metal Outlet Boxes and Isolated Ground Receptacles

Just installed six really nice separate dedicated 20 amp lines (with 6 awg) for my new dedicated listening room.  Decided to use heavy metal outlet boxes so that I could make my six Furutech Receptacles as strong and sturdy as possible.  I also had my electrician run 4-wire 6 agw to the boxes so that we could have one ground wire to the metal receptacle box and then a separate ground wire to the isolated ground screw on the Furutech.

I sent some photos of the setup to a friend of mine (who just happens to be an electrical engineer) and he raised an the issue that since my Furutech Receptacles are metal and they will be screwed into the metal box with metal screws, then we have effectively now tied the two separate grounds together!  Help!  Is that a bad idea?   Is having the box and receptacle setup in this way going to cause issues once my gear is in place; ground loop hums, etc?






stickman451
stickman451 OP
553 posts
 
Jim,

i appreciate you giving me your thoughs on this!  Thanks!   I'd also be curious on almarg thoughts on this; he know's his stuff!

I will run the options that you suggested by my electrician and see what he says.  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.  The extra insultated ground wire would just be left unused.


jea48
4,484 posts
 
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!



stickman451 OP
553 posts
 
As you suggested We may just leave it as is.

Would love to use the Furutech covers, but man are they pricey!! Got any recommendations?

BTW, went momentarily crazy this weekend and bought a Kronos Limited turntable; beautiful table!!!

jea48
4,484 posts
 

stickman451,

Here is what I am using for a duplex plate. Works great.

http://www.legrand.us/passandseymour/duplex-plates/unbreakable/standard/tp8la.aspx

stickman451 OP
553 posts
 
I don't know...i think the black outlet covers sound better than white or bone colored.  😉
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