Single Point Ground


I'm going to have a new room wired with two dedicated power circuits. I've read a single point ground is recommended. Can someone tell me if this is worth the effort and how it is done. I assume it is only important for the dedicated audio circuits.

thanks for any comments,

rogerdn
rogerdn
First, you need explain what your understanding of a single point ground is?

If you are going to have two dedicated branch circuits installed, and they will be installed per NEC and AHJ (authority having jurisdiction) in your area, you will end up with a single point ground.
A single point ground in a audio system could mean only 1 component is grounded. Typically the device that draws the max current. I have heard some 'tube' guys do that to eliminate ground loops/humming.
Jea48
Well I posted because I wanted an explanation of exactly what it was, I've read it is desirable. But if it comes with Code wiring then that is all I need to know. Just puzzled then why it would ever be recommended if it's mandatory. thks for the reply.

Xti16 I have in mind the wiring my electrician will be doing.

rogerdn
Well I posted because I wanted an explanation of exactly what it was, I've read it is desirable. But if it comes with Code wiring then that is all I need to know. Just puzzled then why it would ever be recommended if it's mandatory. thks for the reply.
02-24-09: Rogerdn
Can you give an an example of what you have read? Maybe a forum Link?
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Myths
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Can you give an an example of what you have read? Maybe a forum Link?

Jea48 This is one I recall,

'03-05-08: Saki70
Definetly do the dedicated circuits keeping your digital components on seperate circuits from your analog components .
Also put these on an isolated ground . Are you energy contious ? How many incandesent light bulbs have you switched to flourescent ? It is getting more difficult to isolate the noise makers now a days !
Make sure that your electrician is well versed in isolated grounds . This type of circuit is generally used in the commercial end of the buisness , hospitals and computer centers . I found that residential electricians were aware of isolated grounds but did not know the proper procedure for installing them !
see I have mixed up single point with isolated grounds, sorry. So can I start over are these recommended and how are they implemented.',

But I see I confused single point with isolated grounds,
sorry. So can i start over, is this desirable and how is it done?
Ok from an electrical point of view that's different. By national code all building wiring must have a single point ground. First you need to understand that neutral is a current carrying conductor and earth ground (3rd prong on the pc or outlet) is a non current carrying conductor but there for safety. Neutral and ground - electrically are the same point and there should only ever be one point where they connect.

Isolated grounds on a receptacle the other hand is a little better. Normally conduit is the 'earth ground' and tied directly to the 3rd prong. With Isolated ground you want to run a separate ground wire back to the single ground point - not to neutral.

Also make sure if you do decide to run isolated grounds that those grounds are not better than what exists. Your post made me look at my 'single point ground' and found my ground wire is quite corroded.
Rogerdn,

Isolated grounds?

If the gentleman was speaking of NEC approved branch circuit isolated equipment grounds, as used in commercial or hospital occupancies, then I assume he is talking about the use of isolated grounding type receptacles with insulated equipment grounding conductors.
Regardless, the equipment grounding conductor still has to terminate in the same panel the branch circuit is fed from.

Unless you are going to have the electrician install your two dedicated branch circuits in metallic conduit I see no need for using isolated grounding type receptacles.

If your electrician can use and install NM-B sheathed cable, (Romex is just one manufacture of NM-B), this is considered the best way to go. One cable for each dedicated branch circuit. Dedicated branch circuits only.... No shared neutral multi conductor separate circuit branch circuits!

If the distance from the panel to the outlets is less than 40' to 50' (12-2 with ground) would be ok. Over 50' I would recommend 10-2 W/grd. Many recommend 10 gauge period! One thing about if you install #10 now.... you won't wonder at a later date, what if......

Have the electrician use plastic rough-in boxes for the receptacles if at all possible.

Nylon flexible duplex cover plates.

At the electrical panel make sure the electrician connects the hot conductors of both branch circuits on the same Line, leg, in the panel. If he can on 20 amp breakers directly across from one another.

If you do have to use some type of metallic raceway, conduit, ask him if he can use MC aluminum armor cable.
Solid core copper only, three insulated conductors in each MC cable. Hot, neutral, and equipment grounding conductor. If he can, stick with the plastic receptacle rough-in boxes.

Your electrician not only has to follow NEC but AHJ (authority having jurisdiction) in your area.

Thks both of you for the detailed replies.

Jea48, pls clarify your comment 'If you do have to use some type of metallic raceway, conduit, ask him if he can use MC aluminum armor cable'. Would that be because of a Code requirement ?

If so I am not aware of any, pls confirm you are not recommending a metallic conduit unless required by code.

Is all NM-B sheathed or is there an unsheathed version ?
And what is the sheathing for ?

Is this different from regular cable I would buy at Home Depot ?
Jea48, pls clarify your comment 'If you do have to use some type of metallic raceway, conduit, ask him if he can use MC aluminum armor cable'. Would that be because of a Code requirement ?
Depending on the wiring method the electrician may have to use, he may not be able to use NM-B cable. Might be a (AHJ) issue. If he cannot use NM-B can he use MC cable?

My choice of aluminum armor MC instead of steel armor MC is only because aluminum is non ferrous. Has nothing to do with code.

Is all NM-B sheathed or is there an unsheathed version ?
And what is the sheathing for ?

Sheath only refers to the outer jacket of the NM-B cable.

One other thing I forgot to mention. Have the electrician cut in two separate openings in the wall for each rough-in box for the duplex recepts. Gives you more flexibility on down the road if you want to experiment with receptacle cover plates .

Like I said your electrician will know what needs to be done to meet NEC as well as (AHJ) for your area.

Make sure he goes over the entire job with you before he starts. Asks lots of questions. Make sure he is licensed....
Use 'Nylon flexible duplex cover plates'.

Why this recommendation Jea48 ?

thanks to all for the comments, this has been very helpful.