isolated ground receptacle on a raised cover?

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bradlittle

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How do you ground(bond) the raised cover if you install an isolated ground receptacle on/in it. we are required to bond the raised cover to the box/equipment ground with a regular receptacle, and the requirement isn't different for an isolated ground receptacle. the raised cover doesnt have a specific ground terminal, so how do we bond this? the only thought would be to use a ring terminal and bond to one of the two screws securing the receptacle to the cover. any thoughts? thanks!

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[ February 21, 2005, 06:09 PM: Message edited by: charlie b ]
 
Re: isolated ground receptacle on a raised cover?

250.146(D)and FPN. If you are mounting the Isolated receptacle with a raised metal cover in a metal box, which is grounded by the grounding conductor by a green ground screw, then the cover should be grounded permitted by article 250.146 (A). Hope this helps.

Justin
 
Re: isolated ground receptacle on a raised cover?

The green screw on an IG receptacle only connects to the ground terminal in the receptacle, it is not connected to the yoke or the 6-32 hole for the plate.

The Yoke on an IG is of the self grounding type, the 6-32 screws that hold the device to the box ground the plates and yoke.
 
Re: isolated ground receptacle on a raised cover?

I see no problem with that. Put a ring terminal with a green ground conductor under one of the receptacle mounting screws on the yoke and the other end under a ground screw threaded into the box or wire nutted to the green equipment grounds if they are there.

-Hal
 
Re: isolated ground receptacle on a raised cover?

This has nothing to do with your question - but I have to ask - Why are you using an IG receptacle ?
 
Re: isolated ground receptacle on a raised cover?

the cover is bonded when it is installed on the box


what is the HYPE with IG anyway???
the only IG installations I have seen are Not code-compliant.
what i have seen is people running the 'isolated ground' in branch circuits back to a ground bar that is isolated (like a 'neutral' bar) from the panel it is in, and then simply tied to a grounding electrode like a rod or ground grid..

sounds like a bunch of crap to me ;)
 
Re: isolated ground receptacle on a raised cover?

the cover is bonded when it is installed on the box
Click to expand...
I think that you are correct as the cover is no longer a equipment grounding fault path. And 250.96(A) only requires it to be effectively bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on it.
I think the two 8/32" screws holding the ring to the box would provide this.

Just my thought?
 
Re: isolated ground receptacle on a raised cover?

I think we are over thinking this. :)

The 6-32 supporting screws bond the yoke to the grounded box. The device yoke is electrically connected to the 6-32 mounting hole for the plate screw. The plate is grounded through the 6-32 plate screw just as any metal plate is.
 
Re: isolated ground receptacle on a raised cover?

I'm confused. Is the cover mounted to the box a raised adapter cover (mud ring) designed to go behind drywall or a finished cover (Mulberry cover) that is designed for an exposed surface mounted box?
 
Re: isolated ground receptacle on a raised cover?

I believe he is referring to a raised Mulberry cover but either way, as Bob (iwire) explained, the strap of the isolated ground receptacle is independent from the ground terminal and socket portion of the receptacle. Once you attach the receptacle to the cover it is bonded to that cover and once you attach the cover to the box it completes the ground path. The green (isolated ground) wire from the HCF cable (if that is what he is using) is independent from the equipment ground.

BTW, how were you all able to reply to this post in the forum? When I tried to reply last night the only option was a private message.
 
Re: isolated ground receptacle on a raised cover?

Yep, as others have said, the cover is bonded through the contact of the 8-32's holding it to the 4 sq box. Same as a mud-ring mounted to a 4 sq. Same as the set screw fittings that complete the fault path through the conduit.

If you're in doubt, short out the hot to it and see if it trips the breaker feeding the ckt. :D
 
Re: isolated ground receptacle on a raised cover?

thanks all for your input. i understand that i am thinking deep here, i am an instructor who gets asked these type of questions a lot from apprentices. in my 15+ years of field experience, i have never had to install an isolated ground recept in a surface mount 4 square box 'industrial/raised/mulberry' cover. regular duplex, yes. i understand that the ground terminal is not bonded to the yoke. the way i interpret 250.134 is that this metal cover is to be bonded to the equipment grounding conductor, incase of short circuit, not while it is mounted in the box, but when it is removed from the box, it is still bonded. this is accomplished by bonding the egc to the green screw on a regular recept. in the case of an isolated ground recept (installed due to specs, or to eliminate - reduce- harmonics, common mode interferrence, etc) since the yoke is isolated from the ground screw, so is the cover. if you pull off the cover and for some reason the hot wire comes loose and touches that cover, ouch, you become the path to ground. by bonding the cover to you egc, the path is back where it belongs.

my personal opinion is to put a ring terminal and bond to one of the 6-32s holding the recept in. the isolated ground conductor still makes up on the green terminal on the recept, and no where else, maintaining that isolation. this is a technical violation, because that screw is not listed as a grounding termination.

as another user mentioned, code based installation of an isolated ground recept seem rare, but i am trying to make a few people understand how to do it correctly.
 
Re: isolated ground receptacle on a raised cover?

By Brad: the way i interpret 250.134 is that this metal cover is to be bonded to the equipment grounding conductor, encase of short circuit, not while it is mounted in the box, but when it is removed from the box,
Click to expand...
First you have to understand that code cannot prevent every kind of dangerous thing a person might do. It can not predict the future also. So if a cover is removed exposing live parts while energized and do not know what they are doing. well what's next rubber room's?
The intent of the code is just as it says in 90.1(B):
Compliance therewith and proper maintenance will result in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.
Click to expand...
So if someone removes a cover it is no longer an installation and is no longer code compliant!
And maybe I'm not following your statement but if a cover is removed from the box or receptacle it would no longer be likely to be energized would it? Code only care if the receptacle were to short out and the ungrounded conductor were to make contact with the cover while it is mounted in it's normal place it needs to be bonded. There is no reference to any cover in the code that is required to be bonded after it is removed? The requirement for the bonding of a standard receptacle is much different than the bonding requirement for an isolated grounding receptacle. the latter is found in 250.96.
A standard receptacle if not bonded to the box would loose it's effective fault path for the equipment that is plugged into it if it became loose. So a bonding conductor is required across the raised cover to prevent this. But an isolated receptacle will still have this fault path if it became loose. So only the requirements of 250.96 need to be met to protect the metal parts of the assembly from being energized.
 
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