3 wire feeders

JoeNorm

Senior Member
Location
WA
In my area if we "alter" the service at all at a residence we are almost always required to install a new meter/main with overcorrect protection. The Utility requires it.

What I am confused about is that if the home is old enough to have only a 3 wire feed from the transformer (no EGC), they do not require you to pull the ground. So we go to all the trouble of installing a meter/main but there is no EGC.

This is where I get a little foggy. I am wondering what type of fault makes that new OCPD useful? I'm guessing if there was a Line to Line or Line to neutral short that new breaker would hopefully trip, right?

Why did they start to require an EGC be pulled? I'm curious how and why these rulings evolve.

thanks
 

charlie b

Moderator
Staff member
Location
Seattle, WA
I am not sure I understand what the utility is asking. Let me step (briefly) aside from your question, and ask one of my own. If the meter has not OCPD of its own, then the home's main panel will have a main breaker. Therefore, that panel will be required to have the N-G bonded internal to its enclosure. But if you install a meter that has an OCPD, then the N-G bond has to be made at the meter, the existing N-G bond in the panel has to be removed, and an EGC has to be run from the meter to the panel. Why would the utility require that much trouble?
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
You are incorrectly calling the conductors "feeders". These are service conductors not feeders. Where have you ever seen an EGC with service conductors?
As texie said, you are not using the correct terminology and if you draw it out the way you are describing it from the utility transformer you will see you are simply paralleling the grounded conductor.

Roger
 

winnie

Senior Member
I've never seen a utility feeder with a separate grounded conductor and EGC.

NEC requires a bonding jumper between the grounded conductor and the grounding system. But _if_ the utility provided a separate grounding conductor and EGC, is there any exception to not having the bonding jumper?
 

Carultch

Senior Member
Location
Massachusetts
I've never seen a utility feeder with a separate grounded conductor and EGC.

NEC requires a bonding jumper between the grounded conductor and the grounding system. But _if_ the utility provided a separate grounding conductor and EGC, is there any exception to not having the bonding jumper?
If the utility service conductors provided a separate grounded conductor (aka neutral) and EGC, it would mean that the neutral-to-ground bond is happening inside their transformer, rather than in your service disconnect. This doesn't usually happen in practice, because it is the industry norm to bond a service neutral to ground in the main service disconnect, rather than in a utility-owned transformer.

It is generally only in a customer-owned transformer where you get to do this, and then run a separate grounded conductor and EGC to the first disconnect off of its secondary.
 
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texie

Senior Member
I've never seen a utility feeder with a separate grounded conductor and EGC.

NEC requires a bonding jumper between the grounded conductor and the grounding system. But _if_ the utility provided a separate grounding conductor and EGC, is there any exception to not having the bonding jumper?
The NEC requires the main bonding jumper to be in the service equipment enclosure per 250.24(B). The POCO will also have their end bonded at the service transformer per NESC. In no case will they provide or allow a separate EGC.
 
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