Isolated Ground Recept.

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  #1  
Old 01-25-07, 11:40 AM
Flyboy
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Question Isolated Ground Recept.

Building a home theater and different HT sites have advised to use a hospital type isolated ground recept to reduce noise when using with sensitive elect equipement like projector, electronic equipement & subwoofer speakers. I only have one slot in my main 200 amp panel left open. Have bought double breakers to double up some of the C/Bs but wondered if I can run 3 Isolated Ground direct 12-3 wires to a junction box & then directly to main panel to my one open 20 amp breaker. Shouldn't be a problem with overloading but not sure if this will defeat the purpose of doing a Isolated Ground. WDYT??
 
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  #2  
Old 01-25-07, 11:43 AM
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Do not waste your money on an isolated ground receptacle. It will gain you nothing in your house.

Simply run a dedicated circuit for your home theater. Nothing else is necessary.
 
  #3  
Old 01-25-07, 12:06 PM
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The isolated ground is good when you're using metal conduit and want that extra protection. But as Racraft said, complete waste of time and money for a homeowner. That 12/3 is much harder to work with and is expensive.

I would, however, encourage you to use decent quality receptacles. You can ask for "spec-grade" that will outlast anything you'll do to them. But some people like the crazy orange or green squares you get from hospital grade.
 
  #4  
Old 01-25-07, 12:20 PM
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Isolated grounds are only useful in commercial wiring systems. In a residence, there is no difference between isolated ground and a dedicated circuit. Moreover, there is no legal way to properly install an isolated ground receptacle with NM cable; you would need to use conduit and pull in a dedicated ground conductor (usually green w/ yellow stripe).

Save your money and buy a good surge protector and/or voltage regulating UPS; these will actually protect your electronics.
 
  #5  
Old 01-25-07, 01:51 PM
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There is nothing to isolate your ground from in a home. It is only applicable in industrial setting.
 
  #6  
Old 01-25-07, 06:45 PM
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Originally Posted by joed View Post
There is nothing to isolate your ground from in a home. It is only applicable in industrial setting.
I have to disagree with you on this point. Contrary to popular belief, a ground often carries some small currents due to EMF often related to high freq switching, welders, some motors, flourescent lights, and some really odd situations. The fact is that if those currents are placed on a ground that is attached to a highly sensative device, it can cause some problems. Although I do not think there are very many cases where a residence would have these problems, I can think of a few.

So the purpose of an isolated ground is to actually isolate it from any other ground so yes, there is something to isolate the ground for the A/V equipment from.
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Fubar411 The isolated ground is good when you're using metal conduit and want that extra protection.

That is not why one would use an isolated ground. It is to remove the chance of EMF interference on a sensative circuit. It does not afford any extra protection in itself. As a matter of fact, when using a conduit system, it eliminates the conduit from the ground circuit of anything plugged into the IG recep.
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An isolated ground is allowed in a non-metallic box but you must use a non-conductive face plate unless there is a means within the recep to ground the face plate when attached to the recep.
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If you have a dedicated circuit and I mean totally dedicated including the neutral (no multiwire branch circuits,) you will have an isolated ground by the fact the only attachment of the ground would be at the recep and at the service panel.
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your idea of mixing the grounds , if they are only to the A/V equipment would be a reasonable mid-ground ( not meant to be a pun). Ideally if you could run an independent (isolated) cicuit and ground to each A/V recep, it would be ideal but keeping any other household interference out would be better than nothing.
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Realistically, I don;t know if you would actually gain anything in the big picture but you audio/videophiles seem to be able to hear and see things I never can.
 
  #7  
Old 01-25-07, 08:03 PM
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How would you isolate a ground in a home? The ground wire already runs from the receptacle back to the panel without connecting to anything else. What is there to isolate?
 
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Old 01-25-07, 08:32 PM
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That is why I said if he used a dedicated circuit that was not part of a MWBC, he would in actuality have an iso ground.

If the circuit connected to anything other than the A/V equipment, such as with a MWBC or a shared circuit, he no longer would have an iso ground to the A/V equipment.


He would have an IG if he had a totally dedicated circuit as racraft suggested.
 
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Old 01-26-07, 10:47 AM
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Nap.. thanks for the good IG info. Since I already have the material I need I think I will go ahead and wire them to a junction box & then direct to a 20amp GFCI breaker in the main panel open slot. According to Black&Decker home wiring book (bought at HD p.224) they just show using a 14-3 NM wire with no conduit but a metal receptacle to grd the copper wire to a screw. They have you lable the red wire & connect it to the grd screw on the IG receptacle. In the service panel the white wire to the neutral bar & bare grd to grounding bar. "The red wire (coded green) to the grounding bar or neutral bar, whichever is the shortest path." It looks from the picture that the white "pig tail" from the GFCI also connects to the neutral bar and the black from the new cable connects to GFCI. Does this all sound right to you?

Was going to also use a couple of slim 15amp C/Bs to free up another slot or two so I can wire up the lights & plugs to their own circuit. Or would you recommend just splicing in a light box in the unfinished basement as long as the watts stay below the max suggested 1440 watts?
 
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Old 01-26-07, 10:57 AM
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Do not use 14-3 and attempt to use the red wire as a ground. This is a code violation and is bad advice on the part of the author of that book. This will not pass inspection.

14 gage wire would be a bad choice , in my opinion, anyway. You should run a 20 amp circuit for your home theater. Run a dedicated 20 amp circuit (20 amp breaker and NM 12-2 cable) and out a duplex receptacle on the end.

For the other circuits I suggest that you use the tandem breakers if your panel allows tandems, else I suggest a sub-panel.
 
  #11  
Old 01-26-07, 11:13 AM
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I think Flyboy is saying that he has 12/3 and will use it. The B&D book (I have it as well) does show 14/3 w/ a red as being used as an isolated ground. How else would you do it with jacketed wire? I mean, sure, you can use whatever colors you want when running THHN, but I don't know of any other /3 wire that doesn't have black,white,red. He even indicated he would recode with green tape.

As for the "light box" question, you would be better to use a junction box/handy box.
 
  #12  
Old 01-26-07, 11:17 AM
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The only code legal way to do this is with conduit and individual wires. NM cable is wrong for an isolated ground circuit. Remarking with green tape does not correct the code violation and will not pass inspection.

And since the isolated ground circuit adds nothing to the circuit and serves no purpose, the materials are a waste of money.
 
  #13  
Old 01-26-07, 01:46 PM
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Reusing the red for isolated ground used to legal in Ontario. It is no longer allowed as far as I know.
In a house it connects to the same place as the bare ground so I still don't see the point of an isolated ground.
 
  #14  
Old 01-26-07, 02:46 PM
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if you use a non-metallic box, you only need one ground conductor (EGC). If you run a dedicated circuit to that recep, by virtue of the fact there is nothing else connected to that ground, you do have an IG recep.

So, now, using NM (12-2 w/ground) you have an IG recep and it is code compliant.
 
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Old 01-26-07, 04:02 PM
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Nap.. thanks again for clearing it up. I'll do as you say and use a non-metal box & 12-2 wire (back to HD I go). Any last thoughts as to if it will be to code to wire all three IG recepts to a junction box and then run one 12-2 NM wire to the main service panel & connected to a new GFCI 20Amp C/B?
FYI. I live in Boone Co. N.KY by Cincinnati.

Here is some more info I found discussing IG recepts...

http://www.mikeholt.com/code_forum/archive/index.php/t-57981.html

If you have the time read it and tell me who's right. Sounds to me I need to run dedicated 3 lines to my service panel in order to see any benifit to doing it at all.

Fubar411... I think I can free up two more slots using the slim 2 pole C/Bs. If not I will do the junction box/handy box to splice the wires together for the rest of the recepts & lights. Any preference metal or plastic handy box?

racraft... probably won't make a big dif to run these three dedicated IGs but if it only hurts my pocket book then I'm OK with that. Doesn't sound like I need to run conduit in my area. I was planning on marking the red cable with green tape but doesn't sound like it is to code in some areas. I may just go ahead and run the 12-3 NM wire just in case it is OK in this area. When the Electrical Building Inspector guy comes out to inspect my room wiring I will find out what he has to say about it.
 
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Old 01-26-07, 04:44 PM
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It is not right or to code in any area to mark a red wire green and use it as a ground.

Run one circuit for your home theater. Period. One circuit. One duplex receptacle.
 
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Old 01-26-07, 05:18 PM
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Flyboy: Nap.. thanks again for clearing it up. I'll do as you say and use a non-metal box & 12-2 wire (back to HD I go). Any last thoughts as to if it will be to code to wire all three IG recepts to a junction box and then run one 12-2 NM wire to the main service panel & connected to a new GFCI 20Amp C/B?
FYI. I live in Boone Co. N.KY by Cincinnati.

Here is some more info I found discussing IG recepts...

http://www.mikeholt.com/code_forum/archive/index.php/t-57981.html
==============

Boy, it sounds like some of those guys went to the same school I did for electrical training.

As you read there as well as I posted it here, the best way to run this if you are running multiple receps would be to run dedicated circuit to each but keeping the A/V equipment isolated from the rest of the house would be the next best. Code would not restrict what you have suggested. It merely puts the possibility of interference caused by other equipment on the same EGC.

Remember, if you run this through any metal boxes, the boxes must be grounded. Again, as long as you kept other systems power supply (anything else in the house) not attached to this, you would still effectively have an IG.
 
  #18  
Old 01-27-07, 05:04 AM
Flyboy
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Thanks again for taking the time to explain IGs to me. If I run into any other problems in my wiring I'll let you know.
 
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