receptacle question

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  #1  
Old 01-27-06, 01:46 PM
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receptacle question

What is an isolated ground receptacle and can it be used in a residental application? (garage, basement...etc)

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  #2  
Old 01-27-06, 01:58 PM
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An isolated ground receptacle is a receptacle where the ground terminal is isolated from the rest of the circuit ground.

They can be used in residential applications, but they serve no real purpose except to make the purchaser spend more money. In other words, they serve no purpose in a home setup.
 
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Old 01-27-06, 02:08 PM
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I agree with Bob, but be sure that the circuit is has two grounds back to the panel, one bare and one insulated. If not two grounds, then you need to connect the yolk ground to the isolated ground screw to ensure continuity. Without a metal box, I'm not sure how you'll do that.
http://www.lowes.com/lowes/lkn?actio.../rightNavHowTo
 
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Old 01-27-06, 02:46 PM
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I'm mistaken, you can use a non-metallic box. If you choose a metallic faceplate, then you need a special method of effective grounding of the faceplate. You can check NEC 406.2(D) for the actual text.
 
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Old 01-27-06, 04:49 PM
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If you have only one ground, you use a standard grounding receptivle, where the yoke and the ground contacts share the same screw on the yoke.

I agree. an IG recepticle serves no purpose in normal residential wiring.
 
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Old 01-27-06, 07:54 PM
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IG are often speced in hospitals for sensitive medical equipment; there may also be an element of added safety for patients "hooked" up. I am far from an expert on commercial apps., so that is just a guess. I hope we hear from someone with hospital expertise.

To install an IG in your house would be costly; the benefit would be for computers ,etc, but I have never heard even the geekiest of nerds recommend this extra step in a home installation.
 
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Old 01-28-06, 04:34 AM
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I understand that the IG goes back to the panel and is grounded at the panel.......Is there anyway to reconfigure the recp or to ground it at the box (metal).....I've come across about 6 or 8 of the Ig at no cost and would like to use them in my garage if possible...but do not want to run new cable back to the panel...thanks
 
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Old 01-28-06, 05:22 AM
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You can connect it like a regular receptacle, and ensure that you use nonmetallic faceplate's.
 
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Old 01-28-06, 06:17 AM
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If you mount the IG receptacle in a _grounded_ metal box, and run a grounding pigtail from the box (or ground conductor splice) to the isolated ground screw, then all of the appropriate metal bits will be grounded, and the installation will be safe. Of course, it won't be an 'isolated ground' installation, so this only makes sense if you have some free isolated ground receptacles.

-Jon
 
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Old 01-28-06, 06:25 AM
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Jon,
I haven't seen one recently (because I think there not useful), but is there two ground termination screws, or is the iso ground terminated on the screw, and the yolk strap is bonded to the box by the regular box mounting screws.
I didn't think there was a second ground screw, that is why the NEC just stipulates no metallic faceplate, since it is essentially impossible to bond the strap without the second screw.
 
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Old 01-28-06, 06:37 AM
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Ron,

You bring up a very important point.

All of the IG receptacles that I have seen have proper 'self grounding' clips on the yoke, so that the mounting screw will push the clip against the metal box and properly ground the yoke. But I just did a search, the IG receptacles that Leviton sells have the clip, but I saw at least one IG receptacle on ebay without the clip.

The mounting screws themselves are _not_ considered sufficient to properly ground the receptacle, so if you have IG receptacles without the 'self grounding' clip, then the yoke will not be properly bonded and an insulating coverplate required.

Similarly, if the receptacle is mounted in a plastic box, the yoke would not be grounded.

-Jon
 
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Old 01-28-06, 07:22 AM
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An isolated ground receptacle serves no purpose at all unless installed in a system with metallic conduit. The whole idea here is that the grounded conduit system carries all the electrical noise in the structure and can present it to the equipment attached. An isolated ground uses the conduit as a sheild from the noise and makes the ground connection at the panel, where the noise is dumped to ground (simple explanation - the actual stuff happening is a bit complecated). This way the attached equipment isn't presented with a lot of noise on it's ground. The process is SORT OF similar to the way a coax cable excludes noise so you don't get a crummy picture on a TV. Without the metallic conduit and box for a sheild an isolated ground receptacle simply becomes a receptacle with an ungrounded yoke.

UNK
 
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