Exterior Disconnect - main panel is now a sub?

Specific Inspection Topics Electrical Inspections
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OK. As I said before, it is your right to say whatever you want to say. I asked more pointed questions.

Question:

A home inspector posted this response from ChatGPT to a question he asked about isolating the grounded conductors from the grounding conductors. You, ChatGPT suggested this as a narrative for a home inspection report:

“The neutral bus in subpanels should be electrically isolated from both the equipment grounding bus and the panel enclosure. This prevents neutral current from flowing on grounding paths, which can present shock hazards and interfere with equipment operation. The grounding bus should remain bonded to the panel cabinet and grounding electrode system.”

In that same conversation, you said multiple times that there is a difference between being separated (which is the term used by the NEC) and isolated. Further, you said multiple times that isolated means that there is no conductive path. You gave the inspector conflicting information, but he is now of the opinion that using the word isolated is appropriate when he really means separated. Why did you suggest an obviously flawed narrative which is contrary to fact?

ChatGPT’s answer:

Excellent and important question — and you’re right to call this out.

Here’s what happened, and why that “isolated” phrasing was a mistake:

1. What the NEC actually says

The National Electrical Code (NEC), specifically NEC 250.24(A)(5) and 250.32(B), uses the term “separate” (or “separated”) when referring to the relationship between grounded (neutral) conductors and equipment grounding conductors in a subpanel.

It requires that:

•	The **grounded (neutral) conductor** **must be isolated** (in the sense of **not intentionally connected**) from the **equipment grounding conductors** and the **enclosure** *beyond the service disconnect*.

•	However, “isolated” in NEC language doesn’t mean “no conductive path whatsoever” — it means **no intentional electrical connection** between the grounded and grounding conductors in that panel.

The equipment grounding bus, on the other hand, must be bonded to the panel enclosure.

2. Where ChatGPT’s wording went wrong

The narrative used “isolated” correctly in a conceptual sense (no electrical connection), but failed to distinguish the code terminology (“separated”) from the physical property of electrical isolation (no conductive path at all).

Because “isolated” in electrical engineering can mean completely electrically insulated, it can mislead a home inspector — or worse, a client or electrician — into thinking that there should be no conductive continuity between the neutral bus and the panelboard metal at all, which isn’t always the right way to express it in NEC terms.

In short:

•	**The concept described** (neutral not bonded to ground in subpanels) was correct.

•	**The terminology (“isolated”)** was not NEC-accurate and can easily lead to confusion — especially because *isolated* in electrical language has a more absolute meaning than *separated*.

3. Better wording

A more technically and code-accurate version of that report narrative would be:

“In subpanels, the grounded (neutral) conductors must be separated from the equipment grounding conductors and from the panel enclosure. This ensures neutral current flows only on the intended grounded conductors and not on grounding paths, reducing potential shock hazards and electrical interference. The equipment grounding bus should remain bonded to the panel cabinet and grounding electrode system.”

4. Why the confusion persists

Many AI-generated inspection narratives are based on mixed training data — including informal electrician discussions, older code editions, and non-official summaries — where “isolated” and “separated” are used interchangeably. Without code-context enforcement, the language slips from “practically correct” to “technically sloppy.”

So, to your question:

Why did ChatGPT suggest an obviously flawed narrative which is contrary to fact?

Because the model used the colloquial meaning of “isolated” instead of the NEC’s defined or intended use of “separated.” The underlying concept was right, but the language was imprecise — which, in electrical work and inspection reporting, is enough to make it wrong.

Would you like me to give you a corrected inspection report narrative set (e.g., “satisfactory,” “defect,” and “commentary”) that uses precise NEC language and avoids that ambiguity?

My response:

Yes

ChatGPT:

:green_square: Satisfactory / Acceptable Condition

The grounded (neutral) conductors and equipment grounding conductors are properly separated in this subpanel.

The grounded (neutral) conductors are separated from the equipment grounding conductors and are not bonded to the panel enclosure, as required for downstream subpanels. The equipment grounding bus is correctly bonded to the panel cabinet. This configuration helps ensure neutral current flows only on the intended grounded conductors and not on grounding paths, reducing shock and interference risk.

⸻

:red_square: Deficiency / Correction Recommended

The grounded (neutral) conductors are not properly separated from the equipment grounding conductors and/or the panel enclosure in this subpanel.

Current electrical standards (see NEC requirements for service vs. subpanels) require the grounded (neutral) conductors to be separated from the equipment grounding conductors and from the panel cabinet in downstream subpanels. When neutrals and grounds are bonded in a subpanel, neutral current can travel on grounding paths, which may create shock hazards or erratic equipment operation. Recommend evaluation and correction by a qualified electrician.

⸻

:blue_square: Informational / Commentary

Neutral/ground relationship in service vs. subpanels:

At the service disconnect (main service equipment) the grounded (neutral) conductor is bonded to the grounding system and the enclosure. In downstream subpanels the grounded conductor must be separated and not bonded to the equipment grounding conductors or the panel enclosure. The equipment grounding bus must remain bonded to the panel cabinet and grounding electrode system.

link to the actual conversation:

https://chatgpt.com/share/68ffc573-bbdc-8009-939c-676c9ea5a45d

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https://forum.nachi.org/t/inspector-memes-redux/244780/675

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Okay, I will concede that the NEC-compliant version using “separated” could be the more the precise terminology. Thanks for the follow-through. However, between the common definitions of “isolated” versus “separated,” I feel “isolated” would make more sense to both a layman as well as your average electrician (which ChatGPT, admittedly, was drawing its information). Therefore, I have decided to compromise and use the phrase “electrically isolated (separated)” to make sure my communication is as clear as possible to all audiences. Ultimately, the electrician that is called to investigate the problem will make his or her own diagnosis and use whatever correct or incorrect language they want to describe it to the customer. :slight_smile:

Note to other readers: George and I have not disagreed at all with what the problem is, just how to describe it the most accurately.

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Coincidentally, just yesterday I did a consultation with an homeowner who needs a new service entrance cable, meter socket, service panel, and feeder to an existing panel, which will become a sub-panel. She had bids from four contractors. Three of the four contractors said that they would be separating the neutrals from the equipment grounding conductors to comply with code. One of the four said that he would isolate the neutrals and equipment grounding conductors. Also, just coincidentally, two of the four contractors used to come to my continuing education classes at BGSU. I was disappointed that the guy who said that he was going to isolate them was one of the two who used to used to come to my classes. He and I need to have a talk.

The homeowner was thoroughly confused. She asked me to explain the bids to her so she could do a fair comparison. There were some other differences, like only one mentioned installing a surge suppressor and another one was going to add a laundry circuit. She asked about the grounded conductors and equipment grounding conductors being separated and wondered why only one of the four was going to isolate them. She asked me if she should ask the others to isolate them. I explained to her that none of them are going to isolate them and that the one guy wasn’t using the proper terminology. I assured her that he is a reputable contractor (because he is) and that he would do the job the same as the other three. I told her that “Isolated” is a colloquialism that he shouldn’t be using because it is technically wrong, but that doesn’t make him a bad electrician.

The other thing that was interesting is that the bids were $1,900, $3553, $4140, and $6800 for essentially the same job. None are providing a new load center. They are only providing the outdoor service disconnect where there currently is not one. The low bidder happened to be one of the two who used to come to my continuing education classes since he and his partner started the business in the early 1990s. They have grown to be one of the largest general electrical contractors in the area and probably one of the top five in residential electrical construction. The $4140 guy was the other one who also used to attend my classes. He also started his business around the same time and he is also now also one of the biggest in the area. I have heard of the other two but have no personal experience with them.

I mention all of this because I understand that home inspectors are often pushed to provide repair estimates. The homeowner on this job asked me, before contacting any contractors, what I thought it would cost. I told her that I don’t do estimates because material costs have been going up fast and I don’t try to stay current with pricing. However, I will told her that I would review all her bids and give my opinion on each.

Getting a wide range of bids doesn’t usually surprise me much, but it did this time. I am personally familiar with the $1900 guy and the $4140 guy, but not the other two. The $1900 bid seems the most realistic and reasonable to me. I am out of touch with pricing, but the $3553 guy is at the high end of what I would have guessed. The $4140 guy was going to add a laundry circuit in the general vicinity of the load center, so I suppose that accounts for maybe $100 or so, but still high for the size and scope of the job. I know that he would do a top quality job, but I am equally confident that the $1900 guy would too. The $6800 guy though, yikes, must be living in fantasy land.

I digressed from our original conversation, not only because of the use of “Isolated”, but because of the extremely wide range of the bids for such a small and straightforward job. I wonder what the repair pricing services would have estimated.

I told the homeowner that I recommend focusing on the low bidder. One thing all four bidders did was to assume that the local inspector will approve keeping the existing service panel and converting it to a sub-panel. I suggested that she contact the local inspector to ask if he will approve it because It doesn’t meet current code requirements. The existing location is a problem because of workspace requirements and lack of CFCI and AFCI. This could easily grow from a $1900 job to a $10000 job.

The smartest thing the homeowner did was to contact me. My opinions and recommendations are unbiased (as much as is possible for a human being). My fees are exactly the same regardless of which direction the project goes. There are still some unknowns with the questions about grandfathering (that would be Grand-parenting in New York).

The point of my digression is that inspectors who give repair estimates need to be very careful. My example may seem extreme but it really isn’t. I’ll give one more example.

I did an inspection on a house a few years ago that was owned by a woman who was in hospice. She was not expected to live for more than a few weeks, at most. It’s a long story so I’ll skip a lot of details. The family didn’t want the house to end up in probate. They pressed me for the name of a contractor and a repair estimate. I relented against my better judgment, and gave them a cost estimate and the name of a good friend who is also an electrical contractor.

My friend called me to thank me for the referral but, he also said “From now on, leave the estimating to me”. He asked me if I knew what the material costs were. I did not. I was so far off that it was embarrassing to me.

I mention all of this as a precautionary warning to inspectors who are thinking about giving their customers repair estimates. I often see wide ranges in estimates. I have procedures I’ve developed to ensure that all bidders understand the requirements and the scope of a job. My general advice is not to provide repair estimates.

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Your friend is wise.

I just installed a 20amp outlet for a freezer. The freezer is in a hole of sorts and rates as “hard to move”, so I didn’t get a GFCI breaker. Had I needed that, add another $60. Below is the receipt. Doing this for someone else would add another couple hours of labor. Doing it for a dryer circuit means #8 or #6 and that stuff is around $2/foot per conductor after taxes. The outlet, box and cover is going to cost you $15-$20.

outlet
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To the larger point, I don’t provide repair estimates beyond a very very broad number. Bathroom Remodels start about 15-20 grand. Kitchen are 50-70 grand, pools are 100-200k. Etc. I only will tell them verbally and caveat the hell out of it.

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I don’t try to estimate costs because they are so volatile. Labor costs are easier because they don’t jump around much, so they are more predictable. The main point I was making with the homeowner was that if she wanted to add the laundry circuit, she has a wide margin between the low bidder and the $4140 guy. She took my advice and contacted the local electrical inspector to see if he would allow a variance because the current location doesn’t meet the current requirements. The good news is that he agreed that it would cause undue hardship to relocate the panel, so he will allow it to remain where it is.

I don’t buy building supplies often. When I do, it’s usually only stuff for my own house. Every time I go into anyplace like Home Depot, Lowe’s, or Menards, I walk through the electrical section. The prices just keep skyrocketing. The last time I looked at the price of a box of 14/2 w/ground it was $110. When I was a young electrician, I’d pick up materials for my employer. I remember a 250’ box of 14/2 w/ground NM cable being $7. Graybar used to sell the softcover NEC for $5 if you walked in off the street only for a copy of the NEC. It was free to anyone who bought materials. I got copies of the NEC for my personal use, my office, and all my guys free from Graybar for many years. Now, it is $161 directly from the NFPA.

I know a few home inspectors who use repair pricing services. With contractor prices varying so wildly from one contractor to another and with materials prices being so volatile, I don’t know how the repair pricing services can be of any value.

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That’s your problem!

It’s pretty obvious to all you’ve come to the wrong conclusion!.

It won’t be you! Rather arrogant of you to suggest the thread be closed!

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It would be better to simply say “Isolated” than to say “Electrically isolated” because electrically isolated reinforces that they are electrically isolated, which they are not. By using isolated, you could always try to weasel out of using the wrong word by arguing that you meant mechanically isolated in a particular location. You would still be making a false statement, but electrically isolated would have no reasonable defense.

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Separated is the accurate adjective and leads to zero confusion!

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Yes, of course, you are right. It mystifies me why some inspectors stand so steadfastly against accuracy. I am far from being a psychologist, but I suspect that it has something to do with cognitive biases.

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I think it has more to do with perspective than bias.

Perspective is a way of looking at things, shaped by a person’s background and experience An inspector straight out of InterNACHI school has a different perspective than someone with years of experience in the electrical field, like yourself.

Bias, on the other hand, is a prejudice or inclination that can unfairly skew that perspective, often in favor of or against a particular idea. Biased people often refuse to acknowledge the perspectives of others and will accuse others as being biased.

You can’t change someone’s bias, unless you change their perspective. For the record, you’ve changed my perspective. I no longer use the word “isolated” in the context of a sub panel.

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