Originally Posted By: gbeaumont This post was automatically imported from our archived forum.
Hi Mike,
You know, before I set this question I ran it past 2 very experienced inspectors in this field, who had no issues with it other than the "inspector speak terminology".
and also personaly I am very happy that 70 odd % of our respondents are getting it right.    
Feel free to explain tomorrow why this is a "bad" question
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Mike … That is not a separately derived system, even though the pic shows separate buildings. There is also a bond wire (EGC) shown as running with the feeder, so a N-G bond under 2002 NEC 250.32 would not be allowed.
– Robert O’Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
Mike is correct we can bond at the second building in this example.
Most times I would choose not to, other times it is a better way to go.
The reasons are complicated and will only confuse the main point here. 
In dwelling units any panel that does not have the service disconnect should be isolated neutral.
However run a feeder from that dwelling unit to a separate barn, shed or garage and it is the installers choice if they bond or not.
250.32(B)(1) and 250.32(B)(2) are the relevant code sections.
I am sorry Jerry but I think it would be better if the graphic showed the two panels in / on the same structure / building.
If the graphic had the two panels in one structure the answer would be clear as shown they are two correct answers and neither one is necessarily better then the other.
Each method has good and bad points.
The correct answer to the grapic is not in the list of answers as the correct answer is either bond or don't bond.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
Bob … HI’s do run across sub-panels in out buildings and garages, so I thinks it’s something worth while discussing.
The pic shows the sub-panel in the separate building fed from a breaker in the service panel with a ground/bond wire (EGC) run with the feeders. So there should not be a N-G bond at the sub-panel. That would permit parallel neutral paths ... not good.
NEC 250.32(B)(2) allowing a N-G bond at a separate building would only apply if the was no ground/bond wire run with the feeder.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
roconnor wrote:
NEC 250.32(B)(2) allowing a N-G bond at a separate building would only apply if the was no ground/bond wire run with the feeder.
Correct and as the installer I can choose not to run a grounding conductor, I can use the grounded conductor as the grounding conductor.
When the run is short running a separate grounding conductor is a great way to go.
If it is a long run it is more cost efficient and electrically more efficient to use the grounded conductor as the grounding conductor.
When a ground fault happens which is better electrically for a 100 amp panel. The code minimum 8 AWG grounding conductor or a 3 AWG grounded conductor for the fault current path?
I am more than happy to get in to this, but I have been trying to keep my answers shorter, less technical and with fewer code references. 
Bob 
Originally Posted By: Bob Badger This post was automatically imported from our archived forum.
OK I retract what I said, once I look closely enough at that graphic it shows both a neutral and a ground between the panels in that case the neutral must be isolated.
If there was no EGC run with the feeder the neutral would have to be bonded.
I had just looked at the single line between the panels.
Originally Posted By: roconnor This post was automatically imported from our archived forum.
To find the bond/ground wire … look at the green wire on the right side of the service panel, which continues to the right side of the sub-panel. With this wire the sub-panel shown can NOT have a neutral-ground bond … the neutral MUST be isolated.
Without the pic I agree the question would be vague since it doesn't state the sub-panel is in the house and it is not known if that sub-panel is in a separate building where maybe a bond/ground wire was not run with the feeders.
As Bob pointed out it is okay to run a feeder to a separate building without the bond/ground wire and then have a N-G bond in the sub-panel. But ONLY if it's a separate building without a bond/ground wire run with the feeder.
-- Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong
Originally Posted By: dfrend This post was automatically imported from our archived forum.
Joe, Personally, I like seeing the different perspectives. Debate is a healthy way to learn. Sometimes, opinions have to made, and through the debate we can sometimes realize our opinions were misguided.
As for the diagram, doesn't matter as to copyright as long as Gerry did not plan way ahead of time to use it and it is for educational use. It is called "fair Use under the copyright laws.
From US Code title 17 chapter 1:
(I knew all that instructor training would come in handy  )
Quote:
Sec. 107. - Limitations on exclusive rights: Fair use
Notwithstanding the provisions of sections 106 and 106A, the fair use of a copyrighted work, including such use by reproduction in copies or phonorecords or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for classroom use), scholarship, or research, is not an infringement of copyright.
Originally Posted By: gbeaumont This post was automatically imported from our archived forum.
Hi to all,
Sorry that I decided to pull this question but after realizing that I had used someone elses copywrited materials without authorization I felt it was only fair to undo the damage, besides it was taking me more time than enough to debate the ins and outs of copywrite law, than the issue was worth.
