Bonding 208/120 branch circuits

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Ohms law

Senior Member
Location
Sioux Falls,SD
Do I need to bonding jumper for a metallic raceway into a disconnect that enters into a concentric knockout, even if I run a equipment grounding conductor with the branch circuit.
I understand bonding at services and bonding for over 250volts but I am somewhat confused if this is required if I am not using the conduit as an equipment ground.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
250.96 would likely be your reference.
A metallic conduit system that is serving as a grounding conductor regardless of the presence of an actual wire conductor needs to be bonded where necessary to assure conductivity.
Normally a bonding jumper would not be needed other than on service conduits (250.92), loosely joined raceways (250.98) or as noted in 250.100 for Art 500 installations.
 

augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
A properly installed EMT conduit is an acceptable equipment grounding conductor per 250.118.
Bonding the conduit by means such as bonding jumpers would only be required as noted above or as required by 250.97 for circuits over 250v to ground.
 

Ohms law

Senior Member
Location
Sioux Falls,SD
I know it's acceptable, the question in the matter is if it is required? If you run emt from a panel board that is penetrating to the correct opening per size conduit to a disconnect that has a concentric knockout for 208 single phase branch circuit then would I need a bonding jumper if I have wire type equipment ground?
 

iwire

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Staff member
Location
Massachusetts
I know it's acceptable, the question in the matter is if it is required? If you run emt from a panel board that is penetrating to the correct opening per size conduit to a disconnect that has a concentric knockout for 208 single phase branch circuit then would I need a bonding jumper if I have wire type equipment ground?

It is not a service

It is not over 250 volts to ground


Given those facts what code section would require bonding jumper?
 

Ohms law

Senior Member
Location
Sioux Falls,SD
I'm sorry, are you asking me where would it be or are you asking me if it does exist where is it in the book?
Maybe I'm not being clear or asking the wrong question, when I read 250.96(A)- are to serve as equipment grounding conductors, with or without the use of supplementary equipment grounding conductors, etc. I think it says I need a bonding jumper but at the same time is the conduit required to have a bonding jumper since I have a wire type equipment ground.
I feel stupid even asking this question, I felt I understood but I guess not.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
For purposes of this question, ignore the wire type equipment grounding conductor as the answer is the same if you have it or not.
The conduit does not need any additional bonding beyond the standard locknut unless it is service, over 250v to ground*, loosely jointed or part of an applicable Art 500 install.

* It may not be required in all over 250v to ground ..see the exceptions to 250.97
 

Ohms law

Senior Member
Location
Sioux Falls,SD
No additional bonding even if my situation has eccentric/concentric knockouts and they are not all taken out. Is this what you are saying?
I understand the 250.97 and also know that the ok only j-box that has listed eccentric/concentric knockouts rated for bonding and grounding is for example a 4-square box.
 

ActionDave

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Durango, CO, 10 h 20 min from the winged horses.
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Licensed Electrician
No additional bonding even if my situation has eccentric/concentric knockouts and they are not all taken out. Is this what you are saying? .......
No additional bonding. None. None is needed. None is required. Nothing. No concentric knock outs need to be removed. When there is less than 250V to ground and it is not a service there is nothing extra that needs to be done.
 

Ohms law

Senior Member
Location
Sioux Falls,SD
Gotcha, then what the hell is 250.96(A) for? It refrences "metal raceways" right in the beginning.
So sorry y'all are getting impatient/annoyed. I want to understand this. I have always thought I haven't needed to bond in this situation but a co-worker insisted 250.97(A) requires it for eccentric knockouts.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
Gotcha, then what the hell is 250.96(A) for? It refrences "metal raceways" right in the beginning.
So sorry y'all are getting impatient/annoyed. I want to understand this. I have always thought I haven't needed to bond in this situation but a co-worker insisted 250.97(A) requires it for eccentric knockouts.
No impatience. Highlight where the parts that are in question.
250.96 Bonding Other Enclosures
(A) General. Metal raceways, cable trays, cable armor,
cable sheath, enclosures, frames, fittings, and other metal
non?current-carrying parts that are to serve as equipment
grounding conductors, with or without the use of supple-
mentary equipment grounding conductors, shall be bonded
where necessary to ensure electrical continuity and the ca-
pacity to conduct safely any fault current likely to be im-
posed on them. Any nonconductive paint, enamel, or similar
coating shall be removed at threads, contact points, and con-
tact surfaces or be connected by means of fittings designed
so as to make such removal unnecessary.

250.97 Bonding for Over 250 Volts
For circuits of over 250 volts to ground, the electrical conti-
nuity of metal raceways and cables with metal sheaths that
contain any conductor other than service conductors shall be
ensured by one or more of the methods specified for services
in 250.92(B), except for (B)(1).
Exception: Where oversized, concentric, or eccentric
knockouts are not encountered, or where a box or enclosure
with concentric or eccentric knockouts is listed to provide a
reliable bonding connection, the following methods shall be
permitted:
(1) Threadless couplings and connectors for cables with
metal sheaths
(2) Two locknuts, on rigid metal conduit or intermediate
metal conduit, one inside and one outside of boxes and
cabinets
(3) Fittings with shoulders that seat firmly against the box
or cabinet, such as electrical metallic tubing connec-
tors, flexible metal conduit connectors, and cable con-
nectors, with one locknut on the inside of boxes and
cabinets
(4) Listed fittings
 

Ohms law

Senior Member
Location
Sioux Falls,SD
Iam on the road and all I have is my phone.
What I am hung up on is 250.87(A) stating that metal raceways
Non-current carrying metal parts (in this case EMT conduit) that are to serve as equipment grounding conductor shall be bonded where necessary to ensure electrical continuity and the capacity where to conduct safely any fault current.
My co-worker says because of this wording you need a binding bushing at a concentric knockout ( that is not completely removed) for the 208 single phase.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
Iam on the road and all I have is my phone.
What I am hung up on is 250.87(A) stating that metal raceways
Non-current carrying metal parts (in this case EMT conduit) that are to serve as equipment grounding conductor shall be bonded where necessary to ensure electrical continuity and the capacity where to conduct safely any fault current.
My co-worker says because of this wording you need a binding bushing at a concentric knockout ( that is not completely removed) for the 208 single phase.
He is wrong. 250.8, 250.96, 250.122. If you have access to the handbook there are some helpful pictures.....probably some on MikeHolt.com too.
 

Ohms law

Senior Member
Location
Sioux Falls,SD
I ha ave the 2014 handbook only. Thank you for the responses. I will read them tomorrow when I get up.
Hopefully I did not make anyone want to reach through screen.
 

Ohms law

Senior Member
Location
Sioux Falls,SD
Below 250.118 (2), the authors notes make perfect sense. I understand the wording.
I was right, my co- worker is on the same page as I am now after showing him the handbook with the authors notes. Thank you for being patient with me Action Dave.
 
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