Ground bushing requirements?

herding_cats

herding_cats

Senior Member
Location
Kansas
Occupation
Mechanical Engineer
I'm getting ready to tie in three (3) 200A subpanels from a large 3000A MDP. My question is are grounding bushings required on both ends of the EMT or just one? I'm running 2" EMT on all three subpanels. 208vac 3-phase. If I remember right I just need bushings on the subpanel side?
 
ok awesome. I have grounding bushings on the subpanel side already I'm going to leave them. I'm in an area where inspections don't know what you guys know and don't want trouble/issues. LOL
 
herding_cats said:
ok awesome. I have grounding bushings on the subpanel side already I'm going to leave them. I'm in an area where inspections don't know what you guys know and don't want trouble/issues. LOL
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Not required but also doesn’t hurt anything either , the only time you’d have to worry about additional/enhanced bonding methods when fused conductors are involved at that voltage would be in a hazardous location (250.100), or a metallic raceway/cable assembly between two non metallic boxes/enclosures
 
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tortuga said:
314.3 and its exceptions are not represented accurately in that version
It should say bonding is required at each non-metallic enclosure if the raceway is metallic:

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It’s not incorrect Bonding on one satisfies 314.3 exception 1 . The exception says internal bonding between each entry not at each entry . If a metal raceway leaves a metal box and is properly bonded to that box then and terminates at a nm box/enclosure no additional bonding is required at the nm enclosure it’s bonded internally at the metal box
 

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Jaybone812 said:
It’s not incorrect Bonding on one satisfies 314.3 exception 1 . The exception says internal bonding between each entry not at each entry . If a metal raceway leaves a metal box and is properly bonded to that box then and terminates at a nm box/enclosure no additional bonding is required at the nm enclosure it’s bonded internally at the metal box
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If we have a run of metal raceway going from a box to a nonmetallic box and say its a 240V circuit, 314.3 Exception No. 1 says where the non metallic box has a bonding means provided 'internal' as in in that box that also bonds other all metallic entries to that particular box, the metallic raceway shall be permitted to terminate on that nonmetallic box.
A bonding means outside the nonmetallic box does not qualify as its not 'internal'.
Now if you had a run of EMT between two nonmetallic boxes you'd need a bonding means in each non metallic box not just one.
 
tortuga said:
If we have a run of metal raceway going from a box to a nonmetallic box and say its a 240V circuit, 314.3 Exception No. 1 says where the non metallic box has a bonding means provided 'internal' as in in that box that also bonds other all metallic entries to that particular box, the metallic raceway shall be permitted to terminate on that nonmetallic box.
A bonding means outside the nonmetallic box does not qualify as its not 'internal'.
Now if you had a run of EMT between two nonmetallic boxes you'd need a bonding means in each non metallic box not just one.
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That’s not what exception 1
Says , it says when the metal raceway is bonded internally between all entries , as in electrically continuous , the bonding method does not have fo be internal in the box , if there’s a metal raceway between two nm enclosures one end needs to have a bonding bushing with jumper and then the raceway will be internally bonded between all entries , it’s about keeping metallic raceway electrically continuous ,
It does not say internally bonded at each entry it says between all entries
 
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tortuga said:
If we have a run of metal raceway going from a box to a nonmetallic box and say its a 240V circuit, 314.3 Exception No. 1 says where the non metallic box has a bonding means provided 'internal' as in in that box that also bonds other all metallic entries to that particular box, the metallic raceway shall be permitted to terminate on that nonmetallic box.
A bonding means outside the nonmetallic box does not qualify as its not 'internal'.
Now if you had a run of EMT between two nonmetallic boxes you'd need a bonding means in each non metallic box not just one.
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I said that wrong , if the metal raceway between two nm boxes has contains a wire type egc there only needs to be a bonding bushing with jumper on one end , the bonding bushing will bond the conduit and the wire type egc will be present in the other nm box to keep everything electrically continuous you and everything is bonded between all entries , there doesn’t need to be a bonding bushing on both ends of the raceway at both nm enclosures
 
Jaybone812 said:
I said that wrong , if the metal raceway between two nm boxes has contains a wire type egc there only needs to be a bonding bushing with jumper on one end , the bonding bushing will bond the conduit and the wire type egc will be present in the other nm box to keep everything electrically continuous you and everything is bonded between all entries , there doesn’t need to be a bonding bushing on both ends of the raceway at both nm enclosures
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In the sentence
"Where internal bonding means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables,".
The main topic is the nonmetallic box, the entire phrase "internal bonding means" refers to the methods or techniques used to bond the electrical components together inside the nonmetallic box.
Inside each non metallic box there must be a means to bond each metallic raceway that enters that box.
If the raceway is bonded in another box that does not qualify as thats not inside the nonmetallic box in question.
 
In your prior comment you mentioned it was about their being a method to bond other metal raceways/cables that leave may leave tha nm enclosure If the raceway is bonded properly when it leaves the previous enclosure and there’s a wire type egc present in the raceway which extends into the box, that is a method to bond any other metal raceways/cables that may leave that nm box and its internal in the box ,
I don’t agree that you need to add a bonding bushing with a bonding jumper in the plastic box because its already bonded and there’s a wire type egc available in the box so anything else in that box can use that to achieve the required continuity
 
tortuga said:
In the sentence
"Where internal bonding means are provided between all entries, nonmetallic boxes shall be permitted to be used with metal raceways or metal-armored cables,".
The main topic is the nonmetallic box, the entire phrase "internal bonding means" refers to the methods or techniques used to bond the electrical components together inside the nonmetallic box.
Inside each non metallic box there must be a means to bond each metallic raceway that enters that box.
If the raceway is bonded in another box that does not qualify as thats not inside the nonmetallic box in question.
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I have always envisioned that requirement to mean that the box comes from the factory with a piece of metal that inter-connects individual connector lock-nuts.

Not that they necessarily do or should be made that way, but that's what my mind's eye sees when I read it.

I try to maintain a consistency with materials like I'm sure most of us do.
 
LarryFine said:
I have always envisioned that requirement to mean that the box comes from the factory with a piece of metal that inter-connects individual connector lock-nuts.

Not that they necessarily do or should be made that way, but that's what my mind's eye sees when I read it.

I try to maintain a consistency with materials like I'm sure most of us do.
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For 314.3 exception one I read a method of internal between all entries like this , a metal raceway/cable assembly with a wire type egc leaves a metal enclosure, and the wire type egc bonds the metal enclosure then extends into the nm enclosure , it’s already bonded at the metal box and the wire type egc is internal in the nm box and it can be used to bond any metal raceways/cables that leave that nm enclosure , isn’t the intent to keep everything electrically continuous?
And imagine that’s why Ryan’s flow chart says bonded one end when it speaks to nm enclosures , what does adding a bonding bushing/bonding jumper at the nm enclosure accomplish if it’s already bonded at the other end and there’s a equipment bonding jumper present in the box ?
 
Jaybone812 said:
For 314.3 exception one I read a method of internal between all entries like this , a metal raceway/cable assembly with a wire type egc leaves a metal enclosure, and the wire type egc bonds the metal enclosure then extends into the nm enclosure , it’s already bonded at the metal box and the wire type egc is internal in the nm box and it can be used to bond any metal raceways/cables that leave that nm enclosure , isn’t the intent to keep everything electrically continuous?
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I get what your saying, and I am not saying thats unsafe, and I see that done often.
but what the code is saying is you can't attach a metallic raceway to a non metallic box unless using the exception 1 you have positive connection from metallic raceway entry to the EGC in that box.
The connection to the raceway cannot originate in another box.
 
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