Isolated grounding type receptacles are used mainly in commercial and industrial facilities. Usually they are used for connected loads of sensitive electronic equipment where EMI/RFI noise may be present on electrical metallic conduit, metal wall studs, and such.
99.9% of the time the insulated equipment grounding conductor for an IG receptacle connects to the same ground bar in the electrical panel as the insulated equipment grounding conductors of the non IG receptacles.
In any case the isolated ground, of the IG receptacle, equipment grounding conductor is never connected to an isolated ground rod.
The main sole purpose of the safety equipment ground and the grounding conductor is to carry any ground fault current that may be placed upon it back to the source with the least resistive path as possible.
The earth shall not be considered as an effective ground-fault current path. NEC 250.4 (A)(5)
http://www.aes.org/sections/pnw/pnwrecaps/2005/whitlock/whitlock_pnw05.pdf
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IG recetps do not have to be fed from a GFCI breaker.
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I've been told this is supposedly an acceptable practice but the I/G outlets must run their grounding wires to a separate isolated grounding bar and ultimately out to a buried grounding rod. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>. Dangerous and in violation of NEC code. Works great for hunting fish worms though.... ================================== |
Lissnr, I would suggest you consult an electrician. Isolated grounds are a little more complicated than what you outline above. Perhaps you left some things out for brevity.
With an isolated ground, you typically run the white wire from the silver screw on the receptacle to the neutral bus bar at the panel. You run the black wire from the brass screw on the receptacle to a GFCI breaker at the panel. You code the red wire green and run it from the green screw on the receptacle to the grounding bus bar on the panel. The bare copper wire goes from the grounding screw in the receptacle box to the grounding bus bar on the panel.
An isolated ground receptacle does not need a separate isolated gorunding bar. It uses the grounding bar in the panel. It's just that the isolated ground receptacle does not share a common grounding path back to the ground. |
One more thing to keep in mind is something I've picked up on this forum as I too am installing dedicated lines (Thanks again Gs5556). The #/2 or #/3 represents how many hot leads are in the wire. A 12/2 for example in a standard Romex includes an individually jacketed black wire which is the "Hot", an individually jacketed white wire which is the "neutral" and a bare/wrapped in loose - paper-only copper wire which is the ground wire. On a standard outlet receptacle the black goes to the brass screw, the white to the silver looking screw and the bare copper goes to the green painted screw usually located below and to one side. I have taken the advice of several people and am going with a 12/3 arrangement because these contain 2 hot leads (both are jacketed) and because I want to use a jacketed ground wire instead of bare I will label one of these black hots with green tape and use it as a ground wire to connect to that green ground screw on the terminal. In this case the bare copper wire is simply ignored/unused. This facilitates using Isolated Grounding schemes from whichever outlets you want to run an I/G ground system with. As far as I've been told this is supposedly an acceptable practice but the I/G outlets must run their grounding wires to a separate isolated grounding bar and ultimately out to a buried grounding rod. Does this still sound legitimate to you Gs5556? P.S. My distance from breaker box to outlets is less than 30' each and therefore I'm choosing the much easier to work with 12G instead of the 10G... I hope there's no possibility of audible difference at any time? Good lick with your project. |
Thanks guys for all your input. I have learned a great deal about running these dedicated lines that I didn't know. Especially that the wire lengths used must be the same to avoid a ground differntial between my pieces of equipment. This site is a really great resource for all of us!!
Mark |
Most, if not all, new receptacles have terminals that accomodate 14, 12 and 10 wire. Even the 15-amp 5-15R. The limiting factor is not the wire but the circuit breaker. The breaker must not pass more current than the wire ampacity that's it's connected to. So you could put a set of 500MCM wires on a 20-amp breaker feeding a 15-amp receptacle (that's not physically possible, I'm making a point). In your case, #10 wires are good for 30-amps but when used for a branch receptacle circuit, the breaker can only be 20-amps max. When the breaker limits the current, a larger wire size is not an issue. Correct wire sizes are equivalent to steel beam sizes - you can go bigger than what's needed to do the job if you don't care about money.
Where and why #10 instead of #12 when a 20-amp breaker is the most permitted? When voltage drop is a concern. Generally, #10 is used when there is a 50 foot or more total wire length from panel to receptacle. Less than that, you are wasting money as #12 is more than adequate.
Also keep in mind that any 115 volt device with a UL label can be safely be put on a 15-amp circuit. That's where the confusion lies over 15-amp receptacle with 20-amp breakers. The circuit will never draw the 20-amps as you are limited by code to size your system based on a ten receptacle maximum on a circuit, each one 180 VA, or 1,800 VA (15-amps) total.
Overheating a circuit is an end-user created problem (power strips and extension cords). It's your choice for the wire sizes, #10 will work and fit properly. |
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Bob, it's not the undersized/oversized wire issue that I was referring to. As you state, it's better to have thicker wire. It's the receptacle that I was referring to. Most duplexes are manufactured for 14 or 12 gauge wire, including the hospital grade receptacles that audiophiles often use. If you put a 10 gauge wire in it, the receptacle may overheat and pose a fire hazard if it's not rated for this size of wire. Or the wire won't fit properly in the receptacle. Either the screw on the side won't hold it and the wire will work itself loose with temperature changes, or the little hole at the back for inserting the wire directly into the duplex will be too small. So people may jam it in damaging it. It should say on the duplex itself what size wire you can use. Ten gauge wire is fine. I'm not disputing that. I'm just suggesting that people be careful to do it properly. Also keep in mind that there are often local electrical codes that add to the NEC, thereby imposing stricter requirements. You have to check the area where you live. |
That some outlets may not be rated for larger than 12ga would be the potential issue (connection points not large or secure enough). However, the often recommended Hubbells, PorterPorts and Jena Labs outlets will all handle 10ga wire with no trouble. And I would expect many others will do so as well.
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Mark, I am not following your comment regarding 10AWG wire and a possible code violation. I thought that the NEC specified the minimum gauge for the wiring and that the installation of larger conductors, while overkill from a safety perspective, could do no harm.
As I understand it, undersized conductors can overheat and cause problems to the extent the circuit sees sustained current draw approaching its maximum rated capacity. As a result, using conductors that are smaller than the NEC-specified minumum can pose a hazard and constitutes a violation of the Code. On the other hand, larger conductors (e.g., 10AWG wire in a 20A circuit) will pass with flying colors and never pose a safety hazard in a similar test. What is your perspective on this?
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You can get most of the benefit of dedicated lines, especially for lo-current equipment by use of a large isolation transformer. |
I had my electrician run me a sub panel(8 breakersX15a) for my system.
All eight of my outlets are wired with 10 gauge.Then I had him give me 2X240v for my 20a and 15 Balanced TorusX2.I've
heard 10 gauge was the way to go.I couldn't be happier. |
10/2 will be more than sufficient ........ |
Heads UP! i have done this and learned a great lesson. Make sure all your wires are same length, exactly! If you run any diffrent, you will get a ground differential and have to externally ground all your equipment from one piece to another. Additionally, if you terminate yourself, you can be sure that nothing is nicked, scratched or etched when removing insulation. Next step, which will be the most life changing experience you could have, go solar. Its amazing the difference in sound when you use photons and voltage inverter, directly into your system...best wishes...you are almost there... |
If you're going to install dedicated lines, use 20 amp circuits rather than 15. You would use 12/2 wire for a 20 amp circuit, unless you do a split duplex, in which case you could use 12/3.
Some people may suggest you use 10/2 wire. I would be careful about doing that. More likely than not, the receptacles you use will not be rated for use with 10 gauge wire. It would be a fire hazard and code violation. |
