Isolated Ground and Plastic Boxes


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Old 10-28-03, 11:54 AM
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Question Isolated Ground and Plastic Boxes

I am running a dedicated 15 amp circuit for my home theatre system. I picked up a Leviton orange isolated ground receptacle. The box where the receptacle will be housed is plastic and therefore does not need to be grounded. Will this circuit be a true isolated ground circuit if I only use 12/2 wire? The ground wire will be connected directly to the ground bus in the panel and to the ground screw on the receptacle.

Thanks
 
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Old 10-28-03, 12:59 PM
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A plastic box with a seperate home run for the power all the way to the main panel will be as isolated as you can get.


if I only use 12/2 wire?
You mean 12/2w-gnd right?
 
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Old 10-28-03, 03:09 PM
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Are you using that Black and Decker book?
Isolated grounding circuits are a waste.
 
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Old 10-28-03, 03:51 PM
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In a home there is not really a need or even such a thing as an isolated ground. It is only a consideration in commercial environments.
 
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Old 10-28-03, 04:13 PM
DaveB.inVa
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I dont think hes using the black and decker book. It describes using 12/3 and illegally reidenfiying the red wire.


The orange isolated ground receptacle you paid big bucks for isnt going to do any good! They isolate the grounding pin from the metallic box and conduit. You have no metallic box and conduit to isolate from. You could have used a regular old .69 cent receptacle and have just the same audio quality.

If you want to keep this line free of noise then you can simply run a single 12/2 back to the panel and use a regular receptacle making this a dedicated circuit. In this scenario there are no other loads on the circuit to introduce any noise.

Isolated grounding in itsself is not really needed at all in residential applications. Your using a 120/240v single phase source and dont have all the switching devices and such that cause ground noise. In commercial applications with a 3 phase source harmonics can come into play.

In the end, the BIGGEST element in assuring a clean noise free ground is to completly avoid multiple grounds and make sure the neutral is grounded at a single point.. at the service entrance.
 
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Old 10-28-03, 05:45 PM
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The wire will be 12/2 with ground. I'm using the Leviton IG because it has excellent tightness on plugs and a good wire clamping system on the rear. The 69 cent receptacles are crap and I don't want my good gear plugged into them. I'm trying to get a noise-free environment for my equipment and TV and I'm hoping that by running the ground wire directly from the panel to the source, I will achieve this.
 
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Old 10-28-03, 05:59 PM
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JN: edited to remove inappropriate content.
 

Last edited by John Nelson; 10-28-03 at 07:01 PM.
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Old 10-29-03, 08:48 AM
brickeyee
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Unless the clamping system uses a screw, you cannot use a 12 gage wire in a backstab. Exactly what recep did you get?
 
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Old 10-29-03, 11:00 AM
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I think those are backwired not backstabbed. I see HD is now carrying commercial grade recepts by the box, about 15$ a box.
 
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Old 10-29-03, 11:33 AM
brickeyee
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That is why I asked about the screw. The backwire uses a screw to tighten the clamp. The stabs just use that %$#$ spring.
 
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Old 10-29-03, 01:59 PM
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AudioQuest

In order to use the Leviton IG receptacle you will need to use a grounded metallic box as that is the only way to bond the metal strap of the device, the 6/32 plate screw, and (if used) a metal faceplate.
 
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Old 10-29-03, 02:45 PM
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Now why would you want to Bond anything with an IG recept? The screw is bonded to the ground pin but the strap isnt. The IG recept is intended to be used where the raceway, or pipe is grounded and they want to run seperate insulated wire for ground. Then there is plastic cover installed. If he uses a plastic box and hooks ground wire up to the ground terminal its a done deal. If he used metal box then he would need to jumper to ground the box. Plastic is the way to go,,, but this whole deal has way to much brainpower in to it anyway right from the start. If he wanted a better recept he should have just bought a commercial grade recept,,, (even though it wouldnt have made a lick of difference what recept it was as the only real reason for a better one might be if you were plugging in and out 25 times a day),, and ran a new dedicated wire back to the panel and it would have been done deal no matter what box he used. With romex and wood structure a dedicated circuit is by nature an isolated ground.
 
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Old 10-30-03, 05:57 AM
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The Leviton IG uses a back wire system that tightens two clamps down on the wire. Because I'm using the thicker 12/2 wire, it will be easier just to insert the wire into the rear clamping system rather than try to wrap it around the screw terminals.
 
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Old 10-30-03, 12:58 PM
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Bolted Fault,
Good point. An IG Receptacle has its yolk strap electrically isolated from the third prong of the recept (screw).
The yolk strap needs to be part of the equipment ground since there is no seperate IG conductor back to the panel or bonded metal box.
 
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Old 10-30-03, 07:06 PM
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Ron, you think it would be an issue in a plastic box with a plastic cover since it wouldnt be exposed? I am assuming thats what the B&D book sugests then by running the 3 wire w/g is to bond the metal box and use the red for insulated ground? I say pitch the hospital recept for this job and get a regular one and all these issues go away.
 
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Old 10-31-03, 09:34 PM
CSelectric
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Yes, the IG recepts are backwired. So are the 20Amp commercial grade Levitons (and Hubbels and P&S'S.) You get the exact same clamping mechanism, but at a fraction of the cost.
 
 

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