Seperately Derived System - Inspector issue.

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RobertRheintgen

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We were installing a generator and showed the letter from Bob Cramer from Generac. The inspector is citing section 250.20 of the NEC and 250.20(D) He is saying if the transfer switch does not transfer the neutral (grounded conductor), then the generator has a "solidly connected" grounded circuit conductor and the generator is not a separately derived system. Is there any documentation we can provide to this inspector beyond the Generac letter that may help our situation. He wants a ground rod. Thank you!
 
david luchini said:
The inspector is correct in this regard.
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And I second that as does the NEC definition.

Separately Derived System. A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.
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Roger
 
inspector issue

inspector issue

roger said:
And I second that as does the NEC definition.



Roger
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Hello again, now I am confused. I thought generac and Mike Holt at the conference last year said, we did not have to provide a ground rod outside by the generator connected to the external lug. Is this not true?
 
The question that SDS or non-SDS addresses is not whether there should be a ground rod. It addresses whether there should also be a ground to neutral bond at the generator.


Tapatalk...
 
RobertRheintgen said:
Hello again, now I am confused. I thought generac and Mike Holt at the conference last year said, we did not have to provide a ground rod outside by the generator connected to the external lug. Is this not true?
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I agree if the system is a "Non Seperately Derived System" and the solidly connected neutral makes it that. The inspector is wrong saying it is neccessary for this "Non Seperately Derived System".

Now, if he is asking for a GE because he is calling this a structure then he may have a point but, you would have to make sure the winding(s) of the generator are not factory bonded to the generator frame.

Roger
 
david luchini said:
He wants a ground rod for what purpose?
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Because he can?
If he is saying it is not seperately derived I can't understand his wanting a ground rod unless he is looking at 702.10 (B)
But even then your generator can't be considered portable can it?
 
david luchini said:
Subsequent posts from the OP seem to indicate grounding of the frame.
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+1, but the presence of an EGC between the generator and the panel, separate from the neutral, would do the same thing. All that the ground rod would really do is provide a ground when the wiring from the generator to the panel was disconnected for some reason.
 
In a trasfer switch that transfer the neutral then the ground rod and neutral are bonded together. if the transfer switch does not switch the neutral then the ground and neutral are still bonded at the main service and a grounding means is not required at the generator.

From what I understand.
 
cowboyjwc said:
In a transfer switch that transfer the neutral then the ground rod and neutral are bonded together. if the transfer switch does not switch the neutral then the ground and neutral are still bonded at the main service and a grounding means is not required at the generator.

From what I understand.
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I agree that a bonding means is not required (or allowed) at the generator for non-SDS, but I still feel that the separate structure requirement, as well as manufacturer installation instructions, could be interpreted to require a local ground electrode in either case. And the Code would not prohibit that.
 
RobertRheintgen said:
We were installing a generator and showed the letter from Bob Cramer from Generac. The inspector is citing section 250.20 of the NEC and 250.20(D) He is saying if the transfer switch does not transfer the neutral (grounded conductor), then the generator has a "solidly connected" grounded circuit conductor and the generator is not a separately derived system. Is there any documentation we can provide to this inspector beyond the Generac letter that may help our situation. He wants a ground rod. Thank you!
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What dose this letter say? Can this letter be construed as installation instructions?
 
GoldDigger said:
I agree that a bonding means is not required (or allowed) at the generator for non-SDS, but I still feel that the separate structure requirement, as well as manufacturer installation instructions, could be interpreted to require a local ground electrode in either case. And the Code would not prohibit that.
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Oh I always get one there, but I also think that you could get by with pulling a ground from the building. JMO.
 
It is kinda sticky, is it not.:D
As with all things "built" (and as Iwire points out) one could call it a "separate structure", but again, you are not supplying power to it, it is supplying power to you, but do you have to enforce 225.31, etc for the heater or
control power circuits :D

I have not known of an inspector to require a ground rod at a non-SDS generator for the purpose of meeting 250.32
I have known inspectors to require a ground rod IF generac install instructions require one per 110.3(B).
So, it goes back to earlier posts... why does the inspector want the ground rod ? and what does the Generac letter state ?
 
iwire said:
It has to be, it was built or constructed.
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You must think a remote service is a structure -- A few years back Mr Sargent responded to a question of mine during a NFPA training as to this matter. Electrical equipment is not a structure was the response. Seems to me IMHO that a completed manufactured item placed in a location would not constitute a structure. Now, maybe if you assembled several items to produce a free standing product may be different, but you can still build a remote service and it would still be electrical equipment standing apart from the structure it serves.
 
mwm1752 said:
You must think a remote service is a structure -- A few years back Mr Sargent responded to a question of mine during a NFPA training as to this matter. Electrical equipment is not a structure was the response. Seems to me IMHO that a completed manufactured item placed in a location would not constitute a structure. Now, maybe if you assembled several items to produce a free standing product may be different, but you can still build a remote service and it would still be electrical equipment standing apart from the structure it serves.
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I still fail to see it not being a structure. A structure doesn't have to be built in the place it stands, but it still is built or constructed.

A wood pole (made of natural wood) maybe comes closest to being questionable to being built or constructed. But they usually are treated and have had some cutting or other processing and are not in the same place where they were grown either.

If it stands on it's own and is not dependent on another building or structure for support, it is a separate structure.
 
mwm1752 said:
You must think a remote service is a structure -- A few years back Mr Sargent responded to a question of mine during a NFPA training as to this matter. Electrical equipment is not a structure was the response. Seems to me IMHO that a completed manufactured item placed in a location would not constitute a structure. Now, maybe if you assembled several items to produce a free standing product may be different, but you can still build a remote service and it would still be electrical equipment standing apart from the structure it serves.
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Consider this.

The NEC has a requirement for disconnecting means when we bring power to a structure. 225.31


225.32 goes on to tell us the required location for that disconecting means. There are four exceptions to that section. I think exceptions three and four are worth a looking at.


Exception No. 3: For towers or poles used as lighting standards, the disconnecting means shall be permitted to be located elsewhere on the premises.

Exception No. 4: For poles or similar structures used only for support of signs installed in accordance with Article 600, the disconnecting means shall be permitted to be lo-cated elsewhere on the premises.
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That tells me that the NEC considers things as simple as a pole holding a light 'a structure'. If not there would be no need of those exceptions.


Now perhaps a pile of electrical equipment sitting on the ground is not a structure but as soon as you put a support into the ground and hang the electrical equipment from it you have built or constructed a structure.

In my opinion Mr Sargent was shooting from the hip or maybe his answer was misunderstood.
 
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