Dedicated Circuits/Isolated Grounds

I'm not an electrician but asked a similar question. You DO NOT want to run two separate grounds. Hopefully someone with more knowledge will chime in. I think it's even illegal or against code. What you have in mind may be overkill but putting in several lines while you're at it would be the easiest way to do it anyway.

On a regular outlet the ground screw and pin are bonded to the mounting yolk on the outlet. An isolated ground outlet has the ground isolated from the mounting yolk. In buildings constructed with metal studs,metal outlet boxes are usually also used. When a regular outlet is installed with this type of contruction, the ground is bonded (connected) to all the metal studs in that room and probably the whole building. Electrial noise is introduced into the ground pin of the outlet this way. If an isolated ground outlet is installed the ground will not be bonded to the building metal studs and will not pick up electrical noise. If you install an isolated ground outlet in a metal box you would have to run 2 ground wires the box. One to ground the box and one to ground the outlet. They would both connect to the same ground bar in the panel. The outlet ground has to be insulated so it does not touch any other metal on the way to the outlet. If it did touch metal the isolated ground outlet would be useless. There is no advantage of installing an isolated ground outlet if the outlet box is mounted to wood studs and fed with NM (romex) cable.

There was a nice article in "The Perfect Vision" that addressed the additional ground and dedicated outlets. The author used the additional ground and loved it. I think the article came out in the late summer. I am planning on installing one in the future.

Thanks everyone. Nerspellsner, I am a little confused by the last sentence of your comments. I intend to use romex and hospital grade Hubbell outlets. It's my understanding that the Hubbells have an isolated ground. I also have wood studs and intend to run the ground on each outlet back to the box. Is that correct?

Jaffeassc, your description of what you intend to do is the correct "common" grounding process. What others are talking about here is a totally separate grounding system separate of the main panel. If this is done incorrectly you can end up creating additional noise if the entire house finds the new "separate" grounding the shorter route to earth.

What you had intended will work great, just wire your runs as they would be described in any self wiring book or publication you might be using as your guide.

I would avoid attempting the other "isolated grounding" being discussed, for it could cause problems, it might be illegal and it might void you home owners insurance if you had a fire.

So proceed with your Romex wiring as proposed. Ground the grounding wire to the outlet and back at the main panel as you intended. I would however strongly advise you use 8 ga. wire on all circuits. The cost is marginal, and despite this sounding like overkill, my experience has shown a subtle but noticeable improvement.

jd

Jaffeassc, there is nothing wrong with installing isolated ground outlets in your setup. They cost a bit more and are not needed when the box is mounted to wood studs. You can use regular hospital grade outlets without an isolated ground and save a few bucks. Some people might use isolated ground wiring and outlets if type MC (metal clad) cable or metal conduit is used to feed the outlets even if the metal boxes are mounted to wood studs. The long run of metal surrounding the conductors could introduce some noise into you systemt through the single ground wire connected to the raceway and the outlet. It is a NEC code to ground all metal raceways,enclosures,and boxes. The ground screw to the box must be an approved ground screw and always green in color. You could simply wrap the bare ground wire in the romex cable around the ground screw on the box and then connect it to the outlet. Or use a plastic or fiber outlet box that requires no grounding. Always use the screws on the outlet to secure the wires. Tighten with the loop on the wire going clockwise. If you dont the wire will try to back off the screw when you tighten it. Do not use the push in slots in the back of the outlet. The hospital grade outlets usually have a clamp that the wire goes under and is tightened by the screw. Do not wrap the wire around the screw in this case, use the clamp. Leave 6 inches of wire out of the box to connect to the outlet. Thats a little hard to do with #10 but thats a NEC code too.

JD thanks very much for your input. I thought that I was on the right track but I think I may have confused the issue by bringing up the isolated grounds. One more question though. I was initially going to run 10 gauge wires for the 120 volt circuits, but an "electrician buddy" told me that 10 gauge was too heavy to connect to the 120 outlets. Now you’re suggesting 8 gauge. Is there a specific outlet that you can recommend for 8 gauge wire? My understanding was that the hospital grade Hubbell’s are designed for the heavier wire. Will the Hubbell's work with 8 guage, and/or do I need to find a “real” electrician.

Jaffeassc,
That was a great question. First off, any good electrician will laugh you off the face of the earth if you suggest using anything greater than 12ga. The use of such heavy gauge wire for audio goes against everything they have learned. Hell, it goes against everything I have learned.

Having said that, the heavier the wire, the better the sonics, at least from my experience. I just Google hospital grade electrical outlets and found a number of manufacturers home pages. I found two of two manufacturers who accept 10 ga. I only looked at a couple sites. I use the Wattgate (stupid expensive)after trying most of the high quality outlets. It was a clear improvement, but not until everything else in your system is addressed. This outlet does accept 8 ga. I have tried my Wattgate on a couple other systems and heard very little improvement, so I think your on the right track so fat.

I suggest you research the outlet you want and order it on line. You might talk to Albert Porter, an Audiogon friend who has cryo-treated a number of Hubble outlets and he sells them at cost to us A'gon members. He could tell you the maximum gauge wire they will accept.

jd

Thanks again everyone. I think I've learned more about wiring than I ever intended to know. I'm in the process of researching outlets now (never thought I'd say that either)and it looks like I'll be using the hospital grade Hubbell #'s 8300 (125v) & 8400 (250v). JD, I think I'll pass on the 8 guage (hopefully I won't be sorry) but your right, I already made 2 electricians laugh when I told them I wanted to use 10 gauage. Happy Holidays to all.