# Grounding/bonding bushings?



## smkie (Feb 11, 2010)

I feel that bonding bushings are unclear in the code as to where you need them in relation to the field. Seems that everyone one has their own way whenever I've asked. For example two emt conduits piped from a mdp to feed two 225a subs. Do those need bonding bushings? Or say one hits a pull can on the way what needs to be bonded? If anyone has a better way to explain this I'm missing something in the book would be appreciated


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## HARRY304E (Sep 15, 2010)

smkie said:


> I feel that bonding bushings are unclear in the code as to where you need them in relation to the field. Seems that everyone one has their own way whenever I've asked. For example two emt conduits piped from a mdp to feed two 225a subs. Do those need bonding bushings? Or say one hits a pull can on the way what needs to be bonded? If anyone has a better way to explain this I'm missing something in the book would be appreciated


Read 250.94 (B)


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## bkmichael65 (Mar 25, 2013)

HARRY304E said:


> Read 250.94 (B)


or maybe try 250.92(B)


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## piperunner (Aug 22, 2009)

smkie said:


> I feel that bonding bushings are unclear in the code as to where you need them in relation to the field. Seems that everyone one has their own way whenever I've asked. For example two emt conduits piped from a mdp to feed two 225a subs. Do those need bonding bushings? Or say one hits a pull can on the way what needs to be bonded? If anyone has a better way to explain this I'm missing something in the book would be appreciated



Well if you need them in your specs use them but if not you don't need them one thing you must do in your case bond the pull box with the largest ground running in that box .

Just a plastic bushing is used on number 4 wire and up in size to protect the wire . You don't have to put a bonding bushing on it if you don't want to its up to the electrician .

We use them on flex connections even if not called for we use them on transformers flex connections motors anything that's flex . 


You must run the ground in that conduit thur the lug on that bonding bushing option or use the same size wire and install a jumper from case to lug on bushing .


If your running a ground by itself from point A to point B and its a electrode ground or a main bonding jumper you must BOND on both sides not just one side of conduit run . Like if you run a conduit to protect a ground inside a conduit and its not attached to a panel or a enclosure you ground each end of that run with a grounding bushing .

We like the brass grounding hubs for single runs of ground bonding there the best way to go easy to install and look 100 % better then a grd bushing . If you have a 4/0 a grounding hub is the best straight thur and you tighten it up . spend a little money and save time that's if you have lots of grounding if not just use a regular grounding bushing .


One case is if you have un protected feeders like from a transformer to your service we use bonding bushings or from a generator we use bonding bushings if your in a hospital we use bonding bushings on everything from 12 wire to largest feeder 100%.

So theres nothing saying you have to use it but its a case by case basis .

I know you can read the code book and its general information and everyone you work with does it by how they were trained but 
read your specs and look at the contract drawings there will be a detail of grounding applications .


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## 220/221 (Sep 25, 2007)

The two main places they are required are:

1. Concentric KO's, over 250V to ground

2. Service conductor nipples (from meter can to panel)

The newer solar installations have some bond bushing requirements also I believe the feed from the inverter is also deemed service conductors



> For example two emt conduits piped from a mdp to feed two 225a subs. Do those need bonding bushings?


Nope.

The purpose is to make sure the conduit doesn't get energized in case of a failure. The service conductors are not (adequately) fused so they want any conduit/raceway to be bulletproofed by bonding. They way to bond a nipple is via a bond bushing.

In your example, the conductors have overcurrent protection.

In the case of the higher voltage installations, they don't want to depend on the concentric KO's for a bond because they can sometimes easily get broken loose.


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## piperunner (Aug 22, 2009)

220/221 said:


> The two main places they are required are:
> 
> 1. Concentric KO's, over 250V to ground
> 
> ...


 Well good point we never get panel tubs that have concentric knocks outs I would have never thought of that .


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## ponyboy (Nov 18, 2012)

I believe it's more than just concentric/eccentric KOs. I think the wording is "impaired" connection. Which would include the use of reducing washers and the bottom of transformers etc


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