GROUNDING PHISICAL LIMITATIONS

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Winter Springs Fl
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Electrical Designer
I have a residence where the feed-thru meter and first means of disconnect are 24? apart. We are currently bonding the ground and the neutral together at the first means of disconnect. Per 2011 250.30 (A) (2) we need to run a bonding jumper back to the meter. The electrical contractor is telling us that the only lug on the meter base he can land the jumper on connects directly to the neutral lug. We did not want to bond at this point because this would create a parallel ground and neutral path. We then instructed the electrical contractor to just bond to the meter can only. He stated that the meter base is inherently bonded to the can with no removable bonding screw. We then instructed the electrical contractor to bond everything in the meter can. He stated that the meter base can only accept one ground wire. Does anyone have any suggestions on how to make this code legal without the electrical contractor having to make modifications to the meter base assembly or running parallel ground and neutral conductors?

Bryan
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
Bryan,

You are over thinking the LINE side of the Service Disconnect that houses the Main Bonding Jumper. Your electrical contractor is correct to be pushing back against you with his/her descriptions of various limitations of the materials, especially the construction of the meter socket.

As an Electrical Designer here is the take away for you to mull over: On the LINE side of the Service Disconnect there is only a "Grounded Service Conductor", neither Grounded Conductor nor Equipment Grounding Conductor exist. That is, the "neutral" and the "ground" merge into a single conductor. The answers lay in the Definitions.
 

roger

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Fl
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Retired Electrician
As Al notes, there is no reason for an EGC between the meter and the disconnect, the Grounded (neutral) conductor serves as both.

Roger
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
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retired electrician
I have a residence where the feed-thru meter and first means of disconnect are 24? apart. We are currently bonding the ground and the neutral together at the first means of disconnect. Per 2011 250.30 (A) (2) we need to run a bonding jumper back to the meter. The electrical contractor is telling us that the only lug on the meter base he can land the jumper on connects directly to the neutral lug. We did not want to bond at this point because this would create a parallel ground and neutral path. We then instructed the electrical contractor to just bond to the meter can only. He stated that the meter base is inherently bonded to the can with no removable bonding screw. We then instructed the electrical contractor to bond everything in the meter can. He stated that the meter base can only accept one ground wire. Does anyone have any suggestions on how to make this code legal without the electrical contractor having to make modifications to the meter base assembly or running parallel ground and neutral conductors?

Bryan
250.30 is for separately derived systems. You have a service not a SDS. Nothing in section 250.30 applies to your installation.
 
Location
Winter Springs Fl
Occupation
Electrical Designer
Al,

Prior to this experience I would have considered this a "Grounded Service Conductor" until it hit the first means of disconnect and would be in complete agreement with you however, my engineer pointed out 2011 250.30 (A) (2). This specifically states "If the source of a separately derived system and the first disconnecting means are located in separate enclosures, a supply-side bonding jumper shall be installed with the circuit conductors from the source enclosure to the first disconnecting means".

You stated that the answer lay in definitions. I was hoping to find something that gave a clear definition of where the "Grounded Service Conductor" ended but found nothing. Is there anywhere in the code that you know of that specifically indicates a definition as to where the "Grounded Service Conductor" ends? This would help me make a case for my engineer.

Bryan
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
You stated that the answer lay in definitions. I was hoping to find something that gave a clear definition of where the "Grounded Service Conductor" ended but found nothing. Is there anywhere in the code that you know of that specifically indicates a definition as to where the "Grounded Service Conductor" ends? This would help me make a case for my engineer.
Sure.

Go to Article 100. Spend some time there, reading as if for the first time. I have to do it frequently.
2014 NEC
Article 100 Definitions

Service Conductors.
The conductors from the service point to the service disconnecting means.
 
Location
Winter Springs Fl
Occupation
Electrical Designer
250.30 is for separately derived systems. You have a service not a SDS. Nothing in section 250.30 applies to your installation.

Don,

My understanding was that a service is a "separately derived service". Is there somewhere in the code you can point me to that defines this as NOT a "Separately Derived Service"?

Bryan
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Bryan, follow Al's advice and spend some time reading article 100, it will be a big help.

Roger
 

al hildenbrand

Senior Member
Location
Minnesota
Occupation
Electrical Contractor, Electrical Consultant, Electrical Engineer
Bryan, follow Al's advice and spend some time reading article 100, it will be a big help.

Roger
:cool:

And keep asking questions here. Even though this response today was "wax on, wax off" we all have to hear it from time to time.

One of the longest discussions I've had here, was one where I found myself rather quickly put face to face with the Definition (Article 100) of Outlet. Wow, did I learn a lot. Roger was one of my more interesting antagonists in those discussions. ;)
 

ActionDave

Chief Moderator
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Location
Durango, CO, 10 h 20 min from the winged horses.
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Licensed Electrician
Don,

My understanding was that a service is a "separately derived service". Is there somewhere in the code you can point me to that defines this as NOT a "Separately Derived Service"?

Bryan
I agree with the others.

A Separately Derived SYSTEM is completely different and there is no Separately Derived SERVICE.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Don,

My understanding was that a service is a "separately derived service". Is there somewhere in the code you can point me to that defines this as NOT a "Separately Derived Service"?

Bryan
As others have said, you need to spend some time in Article 100.
Separately Derived System. An electrical source, other than a service, having no direct connection(s) to circuit conductors of any other electrical source other than those established by grounding and bonding connections.
The use and understanding of the NEC starts with the terms that are defined in Article 100.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
:cool:



One of the longest discussions I've had here, was one where I found myself rather quickly put face to face with the Definition (Article 100) of Outlet. Wow, did I learn a lot. Roger was one of my more interesting antagonists in those discussions. ;)
It was one heck of a discussion wasn't it. :)

Roger
 
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