Need a Ground Rod Installed?

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winnie

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Location
Springfield, MA, USA
Occupation
Electric motor research
By the NECs definition of structure, there is no such thing as a detached structure where the NEC is relevant :)

A structure is 'that which is built or constructed'. Wiring is built or constructed. If I construct a building with some wires underground to a pole, I have a single structure, since the building and the pole are continuously connected by a constructed path. :) If I have two separate structures and I run wires between them, I have rendered them a single structure.

-Jon
 
mcclary's electrical

mcclary's electrical

Senior Member
Location
VA
winnie said:
By the NECs definition of structure, there is no such thing as a detached structure where the NEC is relevant :)

A structure is 'that which is built or constructed'. Wiring is built or constructed. If I construct a building with some wires underground to a pole, I have a single structure, since the building and the pole are continuously connected by a constructed path. :) If I have two separate structures and I run wires between them, I have rendered them a single structure.

-Jon
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I agree, and touching on what Dennis said, most inspectors around here DO consider the pumping station a seperate structure, so everything he said applies. GES,,,,and feeder instead of two circuits
 
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Volta

Senior Member
Location
Columbus, Ohio
winnie said:
By the NECs definition of structure, there is no such thing as a detached structure where the NEC is relevant :)

A structure is 'that which is built or constructed'. Wiring is built or constructed. If I construct a building with some wires underground to a pole, I have a single structure, since the building and the pole are continuously connected by a constructed path. :) If I have two separate structures and I run wires between them, I have rendered them a single structure.

-Jon
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Wow- what a thought. It's all one building. Cool!
 
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winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
iwire said:
Because while I think winnie's 'no separate structure theory' is interesting I have no doubt the CMPs will not agree with it.
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Amen.

I think that we would all agree that there really are 'detached structures', and we probably agree on the majority of cases. We'd probably find a few grey area cases that would lead to 600 post threads, and we'd probably find a quite a few things that most of us would agree are 'detached structures' but we'd question if the same rules should apply.

I believe that as worded the current definition of detached structure neither agrees with nor clarifies the common understanding of the term.

-Jon
 
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One-eyed Jack

Senior Member
Location
Scotland Neck, NC
Dennis Alwon said:
I tend to agree with the structure concept but that in itself creates other issues.

Let's look at a septic pump setup. Many of these units require 240v for the pump and 120v for the alarm. In some systems the alarm is tied to one leg of the pump-- problem-- yes. Since the 2008 we now have to have a dp breaker installed which would trip out the alarm on a short circuit or ground fault on the pump. Damn the alarm won't work. This makes this install illegal, at least around here.

Now run two circuits - a 240v circuit for the pump and a 120v circuit for the alarm. Problem again-- 225.30 unless one of the special conditions would apply (I didn't think it would). So if it's a structure, which I say yes to, then there is no legitimate way to wire the septic pump system.

I believe there must be an answer somewhere but as the NEC is written there isn't much that wouldn't qualify as a structure if it is detached from the building serving it. What is the intent-- who knows.
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If it is UL listed and the mfg. instructions require two circuits,which all I have seen do I don't have a problem with it, be it a double pole and a single or two single pole breakers.

True.The definition of structure could use a little more thought.
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
One-eyed Jack said:
If it is UL listed and the mfg. instructions require two circuits,which all I have seen do I don't have a problem with it, be it a double pole and a single or two single pole breakers.

True.The definition of structure could use a little more thought.
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I find that most inspectors overlook this and allow 2 circuits. In orange county, nc they made the manufacturer change the setup of the box so that it could accept 2 circuits. They did not want the breaker to trip and have no alarm. The mfg. complied.
 
radiopet

radiopet

Senior Member
Location
Spotsylvania, VA
rbeard said:
We are going to install a new outdoor MLO subpanel to a conrete pole. It will get fed from a 208/120v 3 phase panel. The new panel will have 3 breakers in it serving a camera and lighting. Since it is not in a building or a structure, do we need to install a ground rod for this new subpanel?
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Code says it is a structure in itself(that which is built)...so yes you will need to establish a grounding electrode system in accordance with NEC 250.50
 
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