System Bonding Jumper

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erickench

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Brooklyn, NY
Let's assume you have a separately derived system consisting of a transformer in it's own enclosure and a disconnect(or overcurrent) device in a separate enclosure. You have two jumpers. One from the transformer neutral to it's own enclosure and the other from the transformer neutral through any connecting conduit to the disconnect/overcurrent enclosure and then connected to the equipment grounding terminal bar. Which of these is the system bonding jumper?
 

erickench

Senior Member
Location
Brooklyn, NY
System bonding jumper inside the disconnect enclosure is easy enough. It's just a jumper from the neutral terminal bar to the EGC bar.
 

erickench

Senior Member
Location
Brooklyn, NY
The system bonding jumper is located in the enclosure that contains the GEC.

Actually the GEC is located at the enclosure containing the system bonding jumper.

The problem here is that I came across an old diagram from the 1990s that shows an SBJ running from the transformer neutral to the EGC terminal bar located at the disconnect. If it's in separate enclosures then which enclosure do you connect the grounding electrode conductor?
 
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Smart $

Esteemed Member
Location
Ohio
Actually the GEC is located at the enclosure containing the system bonding jumper.

The problem here is that I came across an old diagram from the 1990s that shows an SBJ running from the transformer neutral to the EGC terminal bar located at the disconnect. If it's in separate enclosures then which enclosure do you connect the grounding electrode conductor?
A grounding conductor between two different enclosures on the line side of the system disconnecting means is an equipment bonding jumper (EBJ)... no matter what the diagram calls it.
 

erickench

Senior Member
Location
Brooklyn, NY
A grounding conductor between two different enclosures on the line side of the system disconnecting means is an equipment bonding jumper (EBJ)... no matter what the diagram calls it.

Yes, I would agree with that. I would size it in accordance with NEC Table 250.66 and refer to it as a "Supply Side Bonding Jumper" as defined in NEC 250.102(C).
 

don_resqcapt19

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Illinois
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retired electrician
Actually the GEC is located at the enclosure containing the system bonding jumper.

The problem here is that I came across an old diagram from the 1990s that shows an SBJ running from the transformer neutral to the EGC terminal bar located at the disconnect. If it's in separate enclosures then which enclosure do you connect the grounding electrode conductor?
The GEC is connected in the enclosure where the grounded and grounding conductors are connected to each other. The grounding and grounded conductors, in the case of a transformer, can be connected to each other at either the transformer or the OCPD, but not both. No mater where the GEC is connected, a bonding jumper will be required between the transformer and the OCPD.
 

erickench

Senior Member
Location
Brooklyn, NY
So regardless of where the SBJ is located in either the transformer or OCPD enclosures there will always be an equipment bonding jumper between the enclosures and this jumper is sized according to NEC Table 250.66.
 

erickench

Senior Member
Location
Brooklyn, NY
Just looked at a second diagram. Where the SBJ is installed at the OCPD, there is no supply side bonding jumper between the enclosures. Is this wrong?
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Just looked at a second diagram. Where the SBJ is installed at the OCPD, there is no supply side bonding jumper between the enclosures. Is this wrong?

If the system bonding jumper and the GEC are connected at the first disconnecting means you must still bond the transformer enclosure. This is most often done by installing a supply side equipment bonding jumper sized per 250.66.

Chris
 

don_resqcapt19

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retired electrician
A metallic raceway that complies with 250.118 can be used as the supply side bonding jumper.

Chris
I know that the items listed in 250.118 are suitable for use as equipment grounding conductors. What tells me that they are suitable for use as a supply side bonding jumper?
 

raider1

Senior Member
Staff member
Location
Logan, Utah
I know that the items listed in 250.118 are suitable for use as equipment grounding conductors. What tells me that they are suitable for use as a supply side bonding jumper?

There is nothing in 250.30(A)(2) that specifically requires an equipment bonding jumper of the wire type. That section only states that when used it must comply with 250.102(C).

I am not aware of anything in Article 250 that prohibits a metallic raceway from being the equipment bonding jumper on the secondary side of a transformer.

Chris
 

don_resqcapt19

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Location
Illinois
Occupation
retired electrician
...
I am not aware of anything in Article 250 that prohibits a metallic raceway from being the equipment bonding jumper on the secondary side of a transformer.

Chris
I do not see a conduit as meeting the requirements of 250.102(A). I do agree that 250.30(A)(2) implies the use of something other than a wire conductor as the equipment bonding jumper. It doesn't tell us what else can be used, so we jump to 250.102(A) to find that information.
 
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