Outbuilding Feeder

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RD35

Senior Member
Quick background on myself. I worked as a design engineer, project manager, and estimator for a mid-size local electrical contractor for 12 years. Then moved on to a different line of work. Now I am back doing electrical again as a facilities electrical engineer and, again, regularly searching the code for info. So, I seem to remember reading (back around 2006) that an outbuilding panel could be fed without a grounding conductor (3-wire URD /USE with 2-hots and one reduced neutral) so long as a grounding electrode and conductor were set at the outbuilding similar to what is done for a service. If that is still the case, can you all point me to the code section that addresses this issue? Thanks!
 
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__dan

Senior Member
How do you propose to provide an effective fault clearing path, for source feeder faults to ground, when the Earth is not a listed grounding conductor in 250.118.
 

infinity

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Location
New Jersey
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Journeyman Electrician
Quick background on myself. I worked as a design engineer, project manager, and estimator for a mid-size local electrical contractor for 12 years. Then moved on to a different line of work. Now I am back doing electrical again as a facilities electrical engineer and, again, regularly searching the code for info. So, I seem to remember reading (back around 2006) that an outbuilding panel could be fed without a grounding conductor (3-wire URD /USE with 2-hots and one reduced neutral) so long as a grounding electrode and conductor were set at the outbuilding similar to what is done for a service. If that is still the case, can you all point me to the code section that addresses this issue? Thanks!

Your memory serves you well, it was permitted by the NEC prior to the 2008 code cycle. In the 2008 it was removed and required a feeder with an EGC.
 

RD35

Senior Member
Thanks to you all! This gets me a good starting point. Now I can do some more studying and reading on the subject to get back on track with the code changes and the current code rules. Much appreciated!

Had somebody ask about this the other day. They wanted to run USE Aluminum direct burial 3-conductor for a detached workshop because they could buy it for cheap. I told them that, last I knew, it was acceptable to do it that way. But I also qualified my statement by telling them I had been away from the electrical industry for several years and that the code may have changed. Guess I got lucky when I made that last statement!:D
 
On a new install why try to use an old code provision when you can easily run a new 4 wire feeder. Price between a 3 or 4 wire feeder is very small.

A 3 wire feed was never compliant if you had another metallic connection between the buildings (telephone or communications cable, metal water pipe).

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Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
On a new install why try to use an old code provision when you can easily run a new 4 wire feeder. Price between a 3 or 4 wire feeder is very small.

A 3 wire feed was never compliant if you had another metallic connection between the buildings (telephone or communications cable, metal water pipe).

Sent from my RCT6213W22 using Tapatalk

Someone may have an outbuilding a long distance away from the main service panel and want to save money.

If there are not metallic paths between the buildings and never will be, what is the concern?
 

Trey4U

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Location
Alabama
Occupation
Retired Electrical Contractor
Your memory serves you well, it was permitted by the NEC prior to the 2008 code cycle. In the 2008 it was removed and required a feeder with an EGC.

Does this mean I can run a 5 wire system from a 3-phase service panel ( 3 hots, neutral and EGC) to a sub panel and the sub panel doesn't need any grounding electrodes since I have the EGC? Is there a Code article referencing this?
 
Does this mean I can run a 5 wire system from a 3-phase service panel ( 3 hots, neutral and EGC) to a sub panel and the sub panel doesn't need any grounding electrodes since I have the EGC? Is there a Code article referencing this?

You still need a GES if a separate structure. I don't have the code section handy. Someone will post it.
 

Trey4U

Member
Location
Alabama
Occupation
Retired Electrical Contractor
You still need a GES if a separate structure. I don't have the code section handy. Someone will post it.

It's not a separate structure. I'm supplying a sub-distribution panel which will feed 5 small buildings. I always thought having a properly sized EGC negated the need for a driven rod(s)
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
It's not a separate structure. I'm supplying a sub-distribution panel which will feed 5 small buildings. I always thought having a properly sized EGC negated the need for a driven rod(s)
Other than a single circuit (even if a MWBC), a disconnect and electrode are required at each building.
 

charlie b

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Lockport, IL
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The disconnect is required by 225.31, with its location described in 225.32. The electrode is required by 250.32.
 

infinity

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Location
New Jersey
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Journeyman Electrician
Does this mean I can run a 5 wire system from a 3-phase service panel ( 3 hots, neutral and EGC) to a sub panel and the sub panel doesn't need any grounding electrodes since I have the EGC? Is there a Code article referencing this?

If there within the same structure no GES is required for a sub-panel. For a separate structure one is required unless you meet what Larry posted in post #14. Charlie gave you some code references. :)
 

charlie b

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Location
Lockport, IL
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Retired Electrical Engineer
It's not a separate structure. I'm supplying a sub-distribution panel which will feed 5 small buildings.
Unless they are physically attached to one another, perhaps with common walls or a common roof, then each of the 5 buildings is a separate structure. Take a look at the article 100 definition of "structure."

 
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