Article 250.30

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mikehughes8

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According to Article 250.30 (A)1 Exception 2 I am permitted to ground the grounded conductor at both the source and main disconnect as long as a parallel path is not created (the earth is not considered a parallel path).

Am I allowed to do this with multiple disconnects serving different buildings or structures?

As an alternative, can I run an seperate EGC to each building only grounding the grounded conductor at the source?
 
mikehughes8 said:
According to Article 250.30 (A)1 Exception 2 I am permitted to ground the grounded conductor at both the source and main disconnect as long as a parallel path is not created (the earth is not considered a parallel path).

Am I allowed to do this with multiple disconnects serving different buildings or structures?

As an alternative, can I run an seperate EGC to each building only grounding the grounded conductor at the source?
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In 08 it changed , You now have to have a equipment ground and grd. rods , electrode, etc... at each building. The grounded conductor will only be used to ground the equipment at the main disconnect.
So on a 240 single phase you'll need 4 wires two hots neutral and grouning conductor. Neutral and equipment ground Isolated from each other at each building
 
So for the purposes of my first question the generator breaker on a seperately derived system would constitute my main disconnect?

What if the generator were to feed a Main Distribution panel instead of each building separately? Would I then be allowed to ground at both the generator and main disconnect or have my choice between the two?

Thanks in advance
 
mikehughes8 said:
So for the purposes of my first question the generator breaker on a seperately derived system would constitute my main disconnect?

What if the generator were to feed a Main Distribution panel instead of each building separately? Would I then be allowed to ground at both the generator and main disconnect or have my choice between the two?

Thanks in advance
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Any chance you could narrow it down to something more specific ;)

A simple rule is: If you run an EGC in any form, you cannot bond the grounded conductor to ground at both ends.
 
Smart $ said:
Any chance you could narrow it down to something more specific ;)

A simple rule is: If you run an EGC in any form, you cannot bond the grounded conductor to ground at both ends.
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I really like "$'s" answer, and can I add that one establishes a service point,
and then address, work, that service accordingly!
 
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95% or more of the generator installations are not separately derived systems, and 250.30 is not to be referenced.

As has already been mentioned, if the transfer switch does not switch the grounded conductor, the generator wiring is not a separately derived system.
 
Smart $ said:
Any chance you could narrow it down to something more specific ;)

A simple rule is: If you run an EGC in any form, you cannot bond the grounded conductor to ground at both ends.
Click to expand...

I understand that you cannot have and EGC and a bond connecting the grounded conductor to ground. My question is, do I have the option of
1) Running and EGC and not grounding my grounded conductor

or

2) Grounding my grounded conductor and omitting the EGC.

Here are some specific examples (for generators) Each generator has breaker protection.

Generator is acting as the only source and feeds multiple buildings or structures. Each building has its own Main Disconnect.

Can I bond and ground at the generator and run a EGC from each building disconnect back to the source.

Or can I bond the grounded conductor at each disconnect and use each grounded conductor as my EGC.

Multiple generators connected to a 4 -pole transfer switch thats supplies a Main Distribution Panel.

Can I Bond at MDP only and use the grounded conductor as an EGC

Or Bond at each generator (don't bond at the main disconnect) and run separate EGCs

Lastly, bond and ground at both generators and the MDP using the grounded conductor as an EGC.

***If this were a 3-pole transfer would I bond the grounded conductor at the MDP only?
 
Well being you provide your location as NC, let's go with the 2008 NEC...

mikehughes8 said:
I understand that you cannot have and EGC and a bond connecting the grounded conductor to ground. My question is, do I have the option of
1) Running and EGC and not grounding my grounded conductor

or

2) Grounding my grounded conductor and omitting the EGC.
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Well let's stop right here.

Under the 2008 NEC, permanently installed generators must have either a GES if a separately derived system or an EGC (stated in the requirements as an "equipment bonding jumper") sized to 250.66 or 250.122, depending on the locaiton of the OCPD.

So there is no getting around running a grounding conductor, but in the case of an SDS you'd bond your grounded conductor at the generator or at it's disconnect. In the case of a non-SDS, your grounded conductor will be solidly-connected to the service, so no other bonding grounded to grounding is permitted.

mikehughes8 said:
Here are some specific examples (for generators) Each generator has breaker protection.

Generator is acting as the only source and feeds multiple buildings or structures. Each building has its own Main Disconnect.

Can I bond and ground at the generator and run a EGC from each building disconnect back to the source.

Or can I bond the grounded conductor at each disconnect and use each grounded conductor as my EGC.
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The generator would be an SDS, so you would bond at the generator AND run an EGC to each building's disconnect. However, there is a requirement for a GES for each building served (which maintains isolation to the grounded conductor), and a GEC requirement for the generator for building(s) served. IMO, you can run the generator GEC from a structure served in with the feeder conductors and not have to run a separate EGC. Yet, I am uncertain at this point whether you'd have to run a GEC from each structure served (I'd have to reread the req's before commenting).

mikehughes8 said:
Multiple generators connected to a 4 -pole transfer switch thats supplies a Main Distribution Panel.

Can I Bond at MDP only and use the grounded conductor as an EGC
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No. This would be a be SDS installation in that the grounded conductor is switched.

Or Bond at each generator (don't bond at the main disconnect) and run separate EGCs
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You will actually have to run GEC's

Lastly, bond and ground at both generators and the MDP using the grounded conductor as an EGC.
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Any way you go about it, under the 2008 NEC, you cannot use the grounded conductor as an EGC... but again IMO, you can use the GEC's as serving a dual purpose as the EGC.

***If this were a 3-pole transfer would I bond the grounded conductor at the MDP only?
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Yes.

PS: I was a bit in a hurry in typing up this response so someone please check my answers... :grin:
 
Pierre C Belarge said:
95% or more of the generator installations are not separately derived systems, and 250.30 is not to be referenced.

As has already been mentioned, if the transfer switch does not switch the grounded conductor, the generator wiring is not a separately derived system.
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Thats strange I have 95% or more with 4 pole ATS........
 
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