Can someone please explain the following question (questions an inspector should ask themselves during the inspection) included in the Subpanel information from the Residential Electrical Inspection course?
Is the neutral bus isolated from the panel enclosure?
Thanks!
It is one of the requirements in a remote distribution panel (aka, subpanel) for the neutral bus to be separated from the panel enclosure.
What did this course teach you about this scenario? Was it unclear? If so, what are you unclear about? That can help us drill down on answering your question.
There are some subpanels that this doesn’t apply to, such as:
So in this question you’re referring to a sub-panel. I would start with identifying what the panel is. If you’ve concluded that it is a sub-panel then you would need to check that the neutral bus is not bonded to the enclosure meaning no green screw, bonding strap, wire jumper, etc.
One exception could be a sub-panel installed in a remote structure prior to the adoption of the 2008 NEC as mentioned in David’s post.
That’s the first question in my mind before I open a subpanel to inspect it.
I want to see the ground bus bonded to the panel, and the neutral bus isolated from the panel and not have any ground wires attached to it.
Here’s the answer I got from AI that might, or might not, help you to understand this situation. 
why are the neutral wires isolated in a subpanel - Google Search
Neutral wires in a subpanel are isolated from the ground wires to prevent current from unintentionally flowing through the grounding system during normal operation and to ensure a dedicated path for fault current to flow in the event of a ground fault. This separation prevents shock hazards and ensures proper functioning of circuit breakers.
This was a subpanel that I recently inspected that had this defect, among others, that I found in the panel.
That mess has Harry Homeowner writtten all over it. The separate EGC bus is missing and the neutral is not bonded so it is possible that the enclosure could become energized.
I agree that’s what Harry Homeowner electrical work looks like, but there was also a new panel installed and the claim of an “updated electrical system”. The company that did the work slapped their sticker on the panel cover, and they are known to those in the business locally to be hacks, and they proved themselves once again.
This was my first clue.
Here’s the distribution panel they installed, not bad, but notice the grounds and neutrals are seperated in this panel, yet they weren’t in the subpanel. Must’ve had the FNG doing the sub. 
And then there was the live K&T I found. 
So helpful. Not sure how I missed this pic in the content. Thx!
Just WOW! Thanks for the share. This helps a lot.
No. This is one of the things you will see and hear inspectors say far too often. That is unequivocally wrong. Neutrals are NEVER ISOLATED from any electrical panel.
The neutral is always solidly grounded and all parts of the electrical system that are capable of carrying current are bonded to the neutral.
The goal is to connect the neutral to the parts that normally do not carry current and the Earth connection as far upstream as possible; although, there are practical considerations that must be taken into account. They are never to be isolated.
Another, related, term you will see and hear often is floating neutrals. Here again, that is unequivocally wrong. As I stated above, the neutral is ALWAYS SOLIDLY GROUNDED. There are no exceptions in residential electrical systems.
For detailed explanations, refer to IEEE Standard 3003.2 (formerly IEEE 142 and IEEE 1100). The former IEEE 1100 was derived from the older FIPS-PUB 94.
The IEEE Standards do not apply directly to residential electrical systems, but are based on engineering principles that apply across the entire spectrum of electrical systems.
The NEC is the most often cited authoritative document in the residential world but the NEC is neither a training document nor a design guide.
Regardless of what you see or hear from any other source, the IEEE is the ultimate authority when it comes to electrical systems design based on proven engineering principles.
Here is a description and graphic from Mike Holt’s forum which may be helpful. The term to remember is objectionable current (basically current in the wrong place).
“If they’re connected at both ends [service and subpanel] they’re in parallel which makes the EGC system (included EGC’s, metallic raceways and enclosures) all current carrying conductors. The EGC should only carry current under fault conditions.” Forum Moderator
Here is the actual wording from the code referenced above, 2020 NEC:
250.6 Objectionable Current.
(A) Arrangement to Prevent Objectionable Current. The
grounding of electrical systems, circuit conductors, surge
arresters, surge-protective devices, and conductive normally
non-current-carrying metal parts of equipment shall be
installed and arranged in a manner that will prevent objectionable
current.
George, Mikah is an InterNACHI student. She wasn’t asking the question, she was asking what the question means.
Isolated and floating are words that InterNACHI school uses to explain why a grounded conductor cannot be connected to normally non–current-carrying metal parts of equipment.
If there is a better word, you should be lecturing the teacher not the student.
Richard, I answered the student’s question. My answer was true and accurate. It’s information that you can stake your reputation on, unlike the InterNACHI electrical courses.
As for lecturing the teacher is concerned, I have. I went through the entire InterNACHI electrical course a few years ago and made corrections to it when I was in Boulder teaching the electrical course at the HOH for InterNACHI. I had put a lot of work into the project, more than a full week. I went through every sentence and every illustration making corrections.
The course was rife with errors. I gave all the edits to Ben Gromicko. Soon after that InterNACHI made some changes in personnel at the school, including replacing Ron Huffman with April Ware. April didn’t last long and they put Kim Stover in charge. The last I heard, Kim was gone and Ben took over running The school. I don’t know what happened to all the edits I did amid the chaos.
InterNACHI published another short electrical course more recently. It contained some particularly egregious errors on really basic stuff. Frankly, it was embarrassing. It was shameful.
Ben had commented in the forum that the staff wrote the course after I pointed out a couple of the egregious and inexcusable errors.
It is incomprehensible to me why anyone would have someone who is clearly not qualified write a course then publish it without having a subject matter expert review it first.
A lack of knowledge is not nearly as bad as going around thinking that you know what you are doing, and disseminating misinformation, because you are basing what you believe to be true on something you learned from what you believe to be a credible source.
I challenge you or anyone at InterNACHI to name one other member who has done as much as I have over the past 20 years to ensure that members get reliable and accurate information about electricity and electrical systems as I have done.
Most of my participation has been at live events and behind the scenes. All the while, though, I have monitored this forum. I frequently refrain from participating because it is my sincere belief that promoting code oriented discussions in favor of promoting basic understanding of electricity, electrical systems, and code theory ultimately does more harm than good.
During my 25 years as a home inspector, I also worked as a forensic electrical consultant and investigator. It is shameful that so many home inspectors are going around spreading misinformation and no HI industry leaders will step up and try to fix what is increasingly looking like it is hopelessly broken.
I have been asked far too many times insurance investigators and adjusters, and lawyers questions like”Why would he (a home inspector) say something like that? It’s embarrassing because most of them have known that I have taught electrical courses for well more than 40 years, including to home inspectors. For the last ten years all I’ve been able to do is shake my head and say “I don’t know”. The reality, however, is that I do know. I just don’t have the time or the energy to try to explain it every time I’m asked.
With respect to using accurate terminology, that’s a drum I’m been pounding right here in this forum for years.
The best way for home inspectors or anyone else to know how to arrange things in a manner that will prevent objectionable currents is to understand first and foremost how electricity works.
There is too much emphasis being placed on random and disjointed bits and pieces and pieces of the NEC all the while lacking a basic understanding of electricity or electrical systems.
You and I are the only two people who regularly get on this forum who have a solid understanding of electricity and electrical systems. The two non-members who frequently answer questions have both demonstrated a lack of the depth of understanding that is necessary to be an effective teacher.
Thank you George for your contributions to the forum and to the inspection industry.
Here’s the source of the OP’s question from How to Perform Residential Electrical Inspections Course, Grounding and bonding, Panels and Subpanels…
Throughout the course, the terms “isolated” and “floating” are used repetitively, with no clear explanation of what those terms are supposed to mean.
I agree, “isolated” is probably not the best word because it implies no continuity to the panel. Would “insulated” be a more appropriate word?
First, the question in the course is a valid question. What’s important is what the course says the correct answer is The correct answer is NO. If the course material says anything other than an unequivocal NO, it is wrong.
I usually describe the grounded neutral conductors and the equipment grounding conductors as being physically separated from each other in all locations downstream of the first point where they are connected together.
I do also occasionally refer to them as being insulated from each other. Both terms are acceptable.
It is essential to anyone who regularly works with electrical systems to understand that:
Floating neutrals are extraordinarily rare. There are very few electrical systems where a floating neutral will exist. Most electricians and home inspectors will likely never encounter one throughout the course of their career.
A compromise system, which is also relatively rare, is a resistance grounded system. Residential electrical systems NEVER employ resistance grounding.
Even though I have been a strong supporter of InterNACHI for more than 20 years, I cannot in good conscience recommend their electrical training. It pains me to have to say that. I will continue to always support InterNACHI and will continue as a staunch defender and promoter of the association, but I will not compromise on academic integrity.
The discussion of more recent short course I mentioned earlier can probably be found in the electrical forum. I encourage all InterNACHI members to find and read the discussion. I hope corrections were made to it. I was so appalled by the course that I had to step away from InterNACHI for a few minutes. I haven’t looked to see if it was rewritten. I certainly hope for the sake of the members and for InterNACHI as an association that it has been rewritten. As it was originally written, it was a black eye to InterNACHI.
That’s wrong and it can be proven wrong by anyone with an Ohmmeter or a simple continuity tester by simply placing one lead on bare metal on the enclosure and the other on the grounded conductor.
If the grounded conductor were isolated from the panel. There would be no continuity. If there is any continuity, even a high but measurable resistance, they are not isolated.
Manufactures have occasionally caused further confusion by giving things names that are ambiguous, misleading or just confusing. Isolated Ground receptacles are an example. An isolated ground receptacle is one that intended to have an insulated EGC the entire distance between it and the location where the circuit that it is on originates. Combination AFCI is a classic example of a term that is confusing to many people. It was probably a marketing person who came up with the term.
Another confusing term used by manufacturers is isolation transformer. All transformers are either isolation transformers or auto-transformers, with the vast majority of them being isolation transformers. However, manufacturers usually reserve the use of the term isolation transformer for certain particular types of isolation transformers. When a manufacturer refers to a transformer as being an isolation transformer, that doesn’t mean that others aren’t isolation transformers. It means that they have employed additional methods of ensuring that the isolation between primary and secondary windings is maintained in operating conditions where the integrity of the isolation is especially important.
They can do things such coating the windings with a higher dialectic strength insulating material than is needed under most operating conditions.
The term can also refer to harmonics not being passed from one set of windings to another. They may include an electrostatic shield to maintain the purity of the electromagnetic coupling between windings.
A home inspector doesn’t need to know all the various nuances, but a home inspector should have a fundamental understanding of electrical systems and common electrical terminology.
There is no defensible excuse for any school to use incorrect terminology without at least making some attempt to explain that they are using layman terminology and that many terms in the electrical trades are nuanced.
Always a pleasure seeing you here, George.
You taught me about floating neutrals can exist in transformers. I am going back too many years.
It had to do with secondary windings, and I honestly forget the rest.
