Repost insulated throat grounding bushing

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hhsting

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Sorry to repost the following post bit had further question:

I have general questions as follows: what are insulated throat grounding bushing and what are they used for application wise? Can they be used for application such as NEC 2014 section 250.92(B) or 250.97 or not?


I thought the insulated throat grounding bushing is used to connect to ground electrode not for application NEC 2014 section 250.92(B) or NEC 2014 section 250.97? I don’t understand
 

ActionDave

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...I thought the insulated throat grounding bushing is used to connect to ground electrode not for application NEC 2014 section 250.92(B) or NEC 2014 section 250.97? I don’t understand
I don't understand either. What is it that led you to the belief that that a grounding bushing was to be used exclusively for grounding electrode conductors and nothing else?
 

ActionDave

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tom baker

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Look at T&B products, we used their BlackJack grounding bushing exclusively where we needed bond a raceway, mostly this was for 277. They are a specification grade bushing, HDG, SS screws, go on a bare or threaded conduit. A lot of what we did was roadway lighting, so it was outside and need to last for 25+ years. Many contractors will use a very inexpensive bushing, hard to install and won't hold up.
 

roger

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Well I am not saying that plans that state insulated throat ground bushing are using the following. The plans just state insulated throat ground bushing. However when I look up google insulated throat ground bushing found following say used to connect to ground electrode:

The link actually says, "Used with a Locknut to Terminate Threaded Rigid and IMC Conduit to a Box or Enclosure and Connect to Ground Electrode." it can be used a number of ways. It might be worth your company to consider hiring a field experienced person to assist you?

Roger
 

kwired

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I think most the grounding bushings you will find likely have insulated throat.

I don't think there is a general rule that they must have insulating throat though. Other "bushed" methods like a chase nipple are all metallic but have a smooth rounded finish that shouldn't cause damages to conductor insulation.

The "grounding" aspect is for any situation where you may want to assure bonding to the raceway it is attached to and is not limited to situations involving grounding electrode conductors.
 

infinity

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I think most the grounding bushings you will find likely have insulated throat.

I don't think there is a general rule that they must have insulating throat though. Other "bushed" methods like a chase nipple are all metallic but have a smooth rounded finish that shouldn't cause damages to conductor insulation.

The "grounding" aspect is for any situation where you may want to assure bonding to the raceway it is attached to and is not limited to situations involving grounding electrode conductors.
If the conductors are #4 or larger they're required to have an insulated throat or some other insulating material.
 

Carultch

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Massachusetts
I have general questions as follows: what are insulated throat grounding bushing and what are they used for application wise? Can they be used for application such as NEC 2014 section 250.92(B) or 250.97 or not?

I thought the insulated throat grounding bushing is used to connect to ground electrode not for application NEC 2014 section 250.92(B) or NEC 2014 section 250.97? I don’t understand

The insulated throat on the fitting is required if conductors are #4 or larger, or if you terminate with the threaded end of RMC/IMC. Either that, or a plastic bushing. You will find that most bonding bushings come with an integrated insulating throat anyway, so that the bonding bushing can serve the purpose of a bushing in general.

The bonding bushing specifically, is what is required any time you have missing or impaired continuity in the conduit run. If you terminate on a non-metal enclosure, that would be missing continuity. If you terminate where ring knockouts remain, and voltage is over 250V to ground, that would be an example of impaired continuity. Unless listed otherwise, the thin attachments in the knockouts are not "strong enough" to safely withstand faults driven by over 250V to ground, so a bonding bushing and bonding jumper is needed, to form a path that bypasses the chokepoints. 4S boxes for instance, are listed for higher voltage bonding thru their ring KO's. Their ring KO's are also be a lot tougher to remove, in order to achieve this listing.

Bonding bushings are also required at least once on any metal service raceway, and on both sides if it is a metal raceway that contains the GEC.
 
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