Bonding junction

[david]

Per 250.6, you wouldn't have, or would eliminate a parallel path with regard to any grounded conductor. If the SBJ is at the source, then you wouldn't have a second at the disconnect, and vice versa. In other words, you'd keep grounded and grounding conductors isolated at all but the location of the SBJ. As for the redundancy compared to a service transformer, I can only surmise the CMP has there own idea on what grounding is necessary.

250.30(A)(3) Grounding Electrode Conductor, Single Separately Derived System.
The grounding electrode conductor is required to be connected at the same point as SBJ. The buildings grounding electrode system is required to be bonded to the systems neutral at the same point as the SBJ bond to the system neutral.
How is that possible if a SBJ is required at the outside transformer and the SBJ cannot leave the enclosure where it is connected at, the buildings grounding electrode system is required to be bonded at the same point as the connection of the SBJ. You would have to have two system bonding jumpers one at the transformer and one at the MDP for the building.

In that case wouldn’t you size the neutral for threefold purpose? Insuring that it is sized no smaller than 250.66 and no smaller than 12 ? percent of the phase conductors and sized to carry the unbalance.

I really do not see the difference as a particle mater if a building is supplied by a utility transformer (service) or an SDS transformer. The supply to a buildings MDP from a n SDS is not a feeder.

My job and responsibilities here at home do not afford me the time I would like to invest in this forum. So I apologize if at times my intrest here seems hit and miss.

 

[Smart $]

250.30(A)(3) Grounding Electrode Conductor, Single Separately Derived System.
The grounding electrode conductor is required to be connected at the same point as SBJ. The buildings grounding electrode system is required to be bonded to the systems neutral at the same point as the SBJ bond to the system neutral.
How is that possible if a SBJ is required at the outside transformer and the SBJ cannot leave the enclosure where it is connected at, the buildings grounding electrode system is required to be bonded at the same point as the connection of the SBJ. You would have to have two system bonding jumpers one at the transformer and one at the MDP for the building.

AFAICT an SBJ is never required to be at the SDS source... but if it is located at the source, you'd simply have to run the GEC to there. Logical rationale deduces you'd locate the SBJ at the MDP, being it is at the structure... and you'd have to run an SSBJ either way.

In that case wouldn?t you size the neutral for threefold purpose? Insuring that it is sized no smaller than 250.66 and no smaller than 12 ? percent of the phase conductors and sized to carry the unbalance.

That only applies where 250.66 falls short, so sizing is two-fold... but otherwise, yes.

I really do not see the difference as a particle mater if a building is supplied by a utility transformer (service) or an SDS transformer. The supply to a buildings MDP from a n SDS is not a feeder.

Correct, not a feeder AND not service conductors. They are transformer secondary conductors.

 

[david]

FWIW, 250.30(C) was added to the 2011 NEC requiring a grounding electrode connection for outdoor sources. QUOTE]
I have a disadvantage at home, I do not have a copy of the 2011 NEC here so I cannot compare the size of the bond or if it was called a system bonding jumper as you pointed out the bond is now a 2011 NEC requirement. 250.30( C ) in 2011 requires the outside SDS to be earthed and bonded to the enclosure

AFAICT an SBJ is never required to be at the SDS source... but if it is located at the source, you'd simply have to run the GEC to there. Logical rationale deduces you'd locate the SBJ at the MDP, being it is at the structure... and you'd have to run an SSBJ either way.

acourding to the above quote the bond required in 250.30 ( C ) is not called out to be a system bonding jumper

If I understand you correctly then you are saying that the supply side bonding jumper has to be run with the source circuit conductors and since the bond is required by 250.30 ( C ) at the transformer (SDS) then you would simply have to run the grounding electrode conductor to the transformer and do the earthling and bonding at that location.
Three phase conductors, Neutral, Supply side bond conductor, Grounding electrode conductor from the outside SDS to the building. All six conductors from the source to the building.

 

[Smart $]

FWIW, 250.30(C) was added to the 2011 NEC requiring a grounding electrode connection for outdoor sources.

I have a disadvantage at home, I do not have a copy of the 2011 NEC here so I cannot compare the size of the bond or if it was called a system bonding jumper as you pointed out the bond is now a 2011 NEC requirement. 250.30( C ) in 2011 requires the outside SDS to be earthed and bonded to the enclosure

AFAICT an SBJ is never required to be at the SDS source... but if it is located at the source, you'd simply have to run the GEC to there.Logical rationale deduces you'd locate the SBJ at the MDP, being it is at the structure... and you'd have to run an SSBJ either way.

acourding to the above quote the bond required in 250.30 ( C ) is not called out to be a system bonding jumper

Here's 250.30(C)...

(C) Outdoor Source. If the source of the separately derived
system is located outside the building or structure
supplied, a grounding electrode connection shall be made at
the source location to one or more grounding electrodes in
compliance with 250.50. In addition, the installation shall
comply with 250.30(A) for grounded systems or with
250.30(B) for ungrounded systems.

Exception: The grounding electrode conductor connection
for impedance grounded neutral systems shall comply with
250.36 or 250.186, as applicable.

If I understand you correctly then you are saying that the supply side bonding jumper has to be run with the source circuit conductors and since the bond is required by 250.30 ( C ) at the transformer (SDS) then you would simply have to run the grounding electrode conductor to the transformer and do the earthling and bonding at that location.
Three phase conductors, Neutral, Supply side bond conductor, Grounding electrode conductor from the outside SDS to the building. All six conductors from the source to the building.

Interpretation and implementation of 250.30(C) is in the wind. Searching the 2011 ROP (report on proposals) gives no indication. It magically appeared without submitted proposal and no substantiation. On the "user" end, some (perhaps many) have interpreted this new requirement as you have. I do not. I look at as simply requiring an electrode at the transformer, connected to the grounded conductor only (or the enclosure only, for ungrounded and impedance grounded systems). The SSBJ connects to the enclosure only. Grounded and grounding remain isolated, while SBJ is located at MDP. No GEC between electrode or its GEC and the MDP.

 

[david]

Here's 250.30(C)...

​

Interpretation and implementation of 250.30(C) is in the wind. Searching the 2011 ROP (report on proposals) gives no indication. It magically appeared without submitted proposal and no substantiation. On the "user" end, some (perhaps many) have interpreted this new requirement as you have. I do not. I look at as simply requiring an electrode at the transformer, connected to the grounded conductor only (or the enclosure only, for ungrounded and impedance grounded systems). The SSBJ connects to the enclosure only. Grounded and grounding remain isolated, while SBJ is located at MDP. No GEC between electrode or its GEC and the MDP.

Then this needs to be clearly understood if the SDS system (outside transformer) is connected to a grounding electrode conductor earthling the system (neutral only) and someone mistakenly bonds the neutral to the enclosure you have created parallel paths for neutral currents to the building through the supply side grounding conductor and the neutral as soon as the required system bonding jumper and grounding electrode system is installed at the building.

I think the old way of using non metallic raceways or direct buried cables and sizing the neutral to be a multifunction conductor (neutral and fault clearing) when someone grounded and outside transformer was simpler. The bond could be made at both locations and no parallel paths for current from the outside transformer to the building

 

[david luchini]

I really do not see the difference as a particle mater if a building is supplied by a utility transformer (service) or an SDS transformer. The supply to a buildings MDP from a n SDS is not a feeder.

That is not correct. The supply conductors from an SDS ARE undoubtedly a FEEDER. In the case of the source of the SDS being a transformer, they are also transformer secondary conductors.

 

[david]

That is not correct. The supply conductors from an SDS ARE undoubtedly a FEEDER. In the case of the source of the SDS being a transformer, they are also transformer secondary conductors.

I disagree they are at the most a secondary tap (secondary conductors) in the case of 240/120 0r 480/277 there would be no supply side overcurrent protection for all the circuit conductors. They are not defined as a feeder they are defined as secondary conductors for a reason.

How would you define them as a feeder?

I think the rules for isolation of the equipment grounding a grounded conductor when a building is supplied by a feeder has been talked about a lot a think it was mentioned that it?s not a feeder and there are different terms and rules when supplying a building through secondary conductors verses supplying a building through a feeder

 

[Smart $]

That is not correct. The supply conductors from an SDS ARE undoubtedly a FEEDER. In the case of the source of the SDS being a transformer, they are also transformer secondary conductors.

I disagree they are at the most a secondary tap (secondary conductors) in the case of 240/120 0r 480/277 there would be no supply side overcurrent protection for all the circuit conductors. They are not defined as a feeder they are defined as secondary conductors for a reason.

How would you define them as a feeder?..

David L. is correct (my bad earlier)...

Article 100...

Feeder. All circuit conductors between the service equipment,
the source of a separately derived system, or other
power supply source and the final branch-circuit overcurrent
device.

 

[Dbronx]

Yiou need the grounding electrode conductor at the mdp not the sub panels. I am assuming the mdp is attached to the building

The MDP is noy attached to building the sub panels are attached to building

 

[Dbronx]

Need clarification whether transformer is service or separately derived system (SDS). 5-wire would be required if SDS.

The Transformer is a separately derived system

 

[Dbronx]

250.30(A)(3) Grounding Electrode Conductor, Single Separately Derived System.
The grounding electrode conductor is required to be connected at the same point as SBJ. The buildings grounding electrode system is required to be bonded to the systems neutral at the same point as the SBJ bond to the system neutral.
How is that possible if a SBJ is required at the outside transformer and the SBJ cannot leave the enclosure where it is connected at, the buildings grounding electrode system is required to be bonded at the same point as the connection of the SBJ. You would have to have two system bonding jumpers one at the transformer and one at the MDP for the building.

In that case wouldn?t you size the neutral for threefold purpose? Insuring that it is sized no smaller than 250.66 and no smaller than 12 ? percent of the phase conductors and sized to carry the unbalance.

I really do not see the difference as a particle mater if a building is supplied by a utility transformer (service) or an SDS transformer. The supply to a buildings MDP from a n SDS is not a feeder.

My job and responsibilities here at home do not afford me the time I would like to invest in this forum. So I apologize if at times my intrest here seems hit and miss.

What is the meaning of SBJ

 

[Smart $]

What is the meaning of SBJ

SBJ = System Bonding Jumper [250.30(A)(1)]

 

[Smart $]

The MDP is noy attached to building the sub panels are attached to building

How close to building is MDP?

 

[Dbronx]

How close to building is MDP?

40 feet

 

[Smart $]

40 feet

IMO, that is enough distance to require a separate GES (grounding electrode system) established at the MDP (the two ground rods of note).

Getting back to the question of your OP (original post), the junction box should be bonded with the feeder EGC(s) passing through the junction box.

 

[david]

It would be nice to know the where the three elements are in relationship to each other.

We know somewhere outside there is a SDS (transformer) that feeds a MDP (outside) that feeds sub-panels mounted on the (outside) of a building. We assume the sub-panels are for the buildings distribution but that?s just an assumption.

It looks like three different locations that grounding electrode systems need bonded.

 

[Smart $]

...

It looks like three different locations that grounding electrode systems need bonded.

The GES's are bonded through the SSBJ or EGC. There is no requirement for additional bonding.

 

[david]

The GES's are bonded through the SSBJ or EGC. There is no requirement for additional bonding.

I was refering to the need to establish a grounding electrode system at three locations

1st location SDS neutral (only) earthed. Neutral bonded to grounding electrode conductor. Grounded to the grounding electrode at the transformer location. Supply side grounding conductor bonded to the transformer enclosure run with the circuit conductors to the MDP

2nd location at the MD. There has to be some kind of structure supporting the MDP. Another grounding electrode system has to be established here. A system bonding jumper from the neutral to the enclosure. The system bonding jumper to the enclosure will also establish the bond from the neutral to the equipment grounding bus. If the grounding electrodes are connected to the equipment ground bus not directly connected to the neutral bus then a main bonding jumper needs to bond the equipment ground bus to the neutral.

From the MDP he has two feeds to two main disconnects at the building passing through a common junction box where he is going to bond the equipment grounds to the junction box.

3rd location is the building its self. At the building another grounding electrode system will be bonded to the equipment ground buss at the buildings main disconnect location. A grounding electrode conductor most likely will go to two ground rods at the main disconnect location (the Subpanels grouped at this location) a grounding electrode conductor will go from one equipment ground buss to the grounding electrode(s) a tap from the grounding electrode will be run two the second panels equipment grounding bus. He also has to bond the equipment ground bus to any metal water pipe in the building.

So I see as three locations bonding has to be done

AT the transformer neutral(only) bonded to earth. Supply side grounding conductor connected to enclosure

At the MDP the System bonding, to the enclosure, system earthed grounding electrode conductor, perhaps a main bonding jumper depending on where the grounding electrode connection is made.

The building equipment grounds bonded to earth and to any metal water pipe in the building