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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
bflowers
80 posts
 
jea48,

I am in a near identical situation and would love your (or anyone else who knows) feedback.  Don't want to hijack the thread, but I don't see a way to send a direct message on AGon anymore (haven't been on the site for some years now).  

In short, I had a custom room built and spared no expense.  Hired a power consultant who designed a system with a 15KVa isolation transformer and a custom breaker panel that feeds only the audio room. System incorporates isolated grounds and IG outlets.  The advantage I have is that I know how my system should should because I only changed one piece of equipment from my old to new room.   System is Wilson Alexandria, Boulder 2110 pre, 3060 amp (had 2060 before and they sound very similar) and full vivaldi stack.  System had incredible detail and thunderous bass.  Now has decent detail and soggy bass (hyperbole).  After a year, I had the electrician take the isolation transformer out of the system and run a new line from the street to the breaker panel.  Everything is much better now, but still has a layer of syrup over the presentation that shouldn't be there and loose bass.  Room acoustics are a bit different, but the power is the biggest difference.  What gives?  Again happy to take offline if appropriate.
jea48
4,264 posts
 

bflowers said:

System incorporates isolated grounds and IG outlets.

Is the branch circuit wiring installed in metal conduit? Steel or aluminum?

IF yes, does each dedicated branch circuit have its’ own dedicated conduit? A true dedicated branch circuit should never occupy the same raceway, conduit, with other branch circuit wiring.

What is the type of branch circuit wiring the electrician installed?

Example:

Metal conduit with wires installed inside the conduit/s after the conduit was installed?

>

MC or AC armored cable?

http://www.southwire.com/commercial/metalCladCables.htm

Aluminum or steel armor? Solid or stranded conductors?

>

NM-B sheathed cable? (Romex is a trade name)

>

What size of conductors, wires?

Approximate length of the dedicated branch circuit runs from the electrical panel to the wall outlets?

Number of dedicated branch circuits?

Are all the branch circuits, that feed audio equipment connected together by wire interconnects, fed from the same line, leg, in the electrical panel? All from Line 1 or all from Line 2? Not from both L1 and L2.


The advantage I have is that I know how my system should should because I only changed one piece of equipment from my old to new room.


How about the branch circuit wiring in the old room? Was the same type wiring used in the new room? How about the wall rough-in outlet boxes used in the new room compared to the old room. Same? Steel or plastic/fiber boxes?

How about the duplex receptacles. Same as the old room? Duplex cover plates. Same as the old room?

What manufacture, series, style, IG (Isolated Ground) type duplex receptacles did the electrician install? Duplex cover plates installed?


Room acoustics are a bit different,

.....

Jim

bflowers
80 posts
 
In metal conduits.  Single run of 12G braided wire in each conduit.  Run from subpanel is <8 ft in all cases.  Probably 20 or so lines coming of the subpanel.  Don't know about the interconnects.  There are 2 legs, but all my equipment fits on one leg.  Old room had lines slowly added over time.  Amp was running 240 in there as well.  I believe it was wired with 10G solid core cable.  There was a mix of metal and "plastic" conduits and boxes in the old room. ( BTW, had serious ground loops in the old room, but the Boulder gear was fairly impervious to it.  I demoed a single ended Lamm amp and it buzzed like a fiend!)  Using a mix of hubbell and voodoo (cryoed hubbell outlets) in new room.  Plastic plates. 
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