Panel Question

Brain cramp (it’s been a long day)- the main disconnect is on the left - the panel to the right is wired as a service panel. It is connected by conduit and bonded. OK, right? :neutral:


Well “technically” it’s wrong by today’s standards. The knife-switch is the service disconnect, and the breakers are in a distribution (sub) panel.

However, based on the age of the equipment, and the bond between panels, this is likely to be an age-compliant installation - barring (of course) the improperly identified conductors, and I don’t see where the grounding bus is bonded to the second panel.

Thanks Jeff - makes perfect sense. I was a bit worn out last night. I like the term “age-compliant”.

There are a few problems with the installation.

The white feeders to the sub-panel are a dead giveaway of it being the work of an amateur.

There appears to be a white wire coming from a breaker.

There does not appear to be a grounding bushing (aka O.Z. bushing). I can’t say for sure though because the far upper left corner is not visible.

It appears to be a typical split-phase system but the grounded conductor is not visible.

It looks like the nipple between the two cabinets is entering the safety switch cabinet through a concentric KO so there should be a bonding jumper and a grounding bushing. The inside right wall of the safety switch is not visible but it doesn’t look as though there is a bonding jumper.

The safety-switch is a NEMA 1 and the fuses are Class R so the switch is probably suitable for use as service equipment but that should always be verified. It should say on the nomenclature tag.

There is nothing wrong with using Class R fuses in a house but their presence often indicates that the installer got a discount (like a 5-finger discount). Incidentally, the fuses are almost certainly type FRN but are definitely not FRN-R. If they were FRN-R, the post should be visible on the bottom of the fuse holders. Except in very rare situations (AFC exceeding 10kA), residential stuff is usually Class H (which is rated for 10kAIC).

The cabinet on the right appears to be a late 1980’s or 1990’s vintage. It is difficult to say for sure but look at the amount of open space. Older boxes tended to be more compact. The deficiencies I can see have all been prohibited by the NEC since at least the 1971 Edition.

When I see an installation like this, it would not be the two boxes that would concern me the most. I’d be really concerned about all the stuff I can’t see. They way I figure it, they probably didn’t get all this stuff wrong then do everything else in the house right.

**[FONT=Times New Roman][size=2]


[size=2][FONT=Times New Roman]Why would he need a bonding bushing even with ecc or concen on the load side of the service disconnect george? If the locknuts cut into the panel to form the bond going to the feeder conductors then why would he need to comply with 250.92(B)(4) as these are not service conductors or service bonding.

250.96 Bonding Other Enclosures.

**(A) General. **
[/size][/FONT][FONT=Times New Roman][size=2]Metal raceways, cable trays, cable armor,[/size][/FONT]
[size=2][FONT=Times New Roman]cable sheath, enclosures, frames, fittings, and other metal
non–current-carrying parts that are to serve as grounding
conductors, with or without the use of supplementary
equipment grounding conductors, shall be bonded where
necessary to ensure electrical continuity and the capacity to
conduct safely any fault current likely to be imposed on
them. Any nonconductive paint, enamel, or similar coating
shall be removed at threads, contact points, and contact
surfaces or be connected by means of fittings designed so
as to make such removal unnecessary.

On the other issues…I believe everyone has covered them fine.

Thanks for your responses guys. It definitely seemed like non-professional work - the drop was rubbing against the metal trim, lots of ungrounded and reversed polarity outlets throughout. Fortunately for my clients, their uncle is a licensed electrician and they plan to update the system before moving in.
As far as a grounding bushing goes, there was one on the right panel - I blew that section of the photo up.



IMG_2726 copy.JPG


A bonding jumper and bushing are required for a couple of reasons. It is part of the service equipment assembly. Also, the connecting points on a concentric KO must be suitable for carrying fault currents. It is possible but unlikely that they are rated as being suitable for bonding.

Is it part of the service conductors George?..It is the conductors from the load side of the service disconnection means. Would they not be Feeders at this point and service assured bonding not required.

Also, the ECC and CONC. requirement applies to service bonding.

[FONT=Times New Roman]size=2 Method of Bonding at the Service. [/size][/FONT]
[FONT=Times New Roman][size=2]Electrical continuity[/size][/FONT]
[size=2][FONT=Times New Roman]at service equipment, service raceways, and service[/FONT][/size]
[size=2][FONT=Times New Roman]conductor enclosures shall be ensured by one of the following

(1) Bonding equipment to the grounded service conductor
in a manner provided in 250.8
(2) Connections utilizing threaded couplings or threaded
bosses on enclosures where made up wrenchtight
(3) Threadless couplings and connectors where made up
tight for metal raceways and metal-clad cables
(4) Other listed devices, such as bonding-type locknuts,
bushings, or bushings with bonding jumpers
Bonding jumpers meeting the other requirements of this
article shall be used around concentric or eccentric knockouts
that are punched or otherwise formed so as to impair
the electrical connection to ground. Standard locknuts or
bushings shall not be the sole means for the bonding required
by this section.


[size=3][FONT=Times New Roman]From where I see it those conductors and nippled on the load side of the[/FONT][/size]
[size=3][FONT=Times New Roman]service disconnect are feeders and since we are not dealing with 277 or

480 the ECC and CONC. play no role. Check out some of Mike Holts
images regarding 250.92.



Hi Paul, I don’t want to (nor will I) get involved in a protracted debate over provisions of the NEC. I realize that you are very knowledgeable of the NEC, that you are an NEC expert. I am conversant in the NEC but I am not an expert. I realized immediately after posting my comments that I had mentioned the NEC. I knew that I should not have done that. I ought to have removed that reference. I inadvertently violated one of my own rules of not citing codes on home inspection message boards.

I will say that I respectfully would like to offer an alternative interpretation of the requirement. We are not looking at this from the same viewpoint but, that’s OK. Before I go on, I want to be perfectly clear about the fact that I have great respect for both you and Mike Holt. Also, I am not suggesting that my interpretation is necessarily right or that yours is wrong. I would like to explain my reasons for my interpretation.

If I am not mistaken, you, Mike Holt, and I have similar backgrounds. We teach NEC to electricians and electrical contractors, are licensed master electricians, are licensed electrical contractors, have degrees in electrical engineering, work or have worked as electrical inspectors, etc. In other words, our interpretations may not be the same but that is not to say that one is any more or less valid than another’s interpretation. You certainly made a cogent argument in defense of your position. My interpretation of the requirement is undoubtedly biased by the fact that this is the way I was taught during my apprenticeship. It was a requirement when I was at Fort Leonard Wood in the 1970s and a local requirement in the jurisdictions in which I have worked throughout most of my career.

Your comments are based on the NEC. That’s fair; especially in light of the fact that I mentioned the NEC in my original message. During the years I worked as an electrician, the NEC was not only at the center of my universe, it was the universe. It still is at the center today but things changed after I shifted from being an electrician to being an engineer and then again when I started doing electrical consulting, fire investigations, and expert witness work. In my NEC classes, I bring in about 30 or 40 other codes and standards, all of which are incorporated into the NEC by direct or indirect reference. I do this to make a point. The NEC is the hub of standards in our trade but it is not the sole governing body of literature. It is one of many governing bodies of literature.

When preparing for trial, lawyers will often bring together experts with opposing opinions to debate the issues. They want to see who can make the most compelling arguments. During these debates, the NEC usually provides the starting point for discussion but we usually spend very little time with the NEC.

We quickly move into other standards such as other NFPA codes and standards (IM-94, 921, 70B, 72, 79, etc), The National Electrical Safety code, the IEEE Color Book standards (specifically Green and Emerald for grounding and bonding), the UL standards (such as the UL White Book), OSHA, ICC, State and local codes, NEMA, IEC, and so on. It is very common for the other standards to directly conflict with the NEC or to be more restrictive.

I have been involved in many of these types of debates. I have many times come away from the experience with a completely new or altered opinion. I’ve also learned that it is possible for two experts to have completely opposing opinions but neither of them are necessarily wrong.

There are several points of contention in the industry with respect to concentric and eccentric KOs. UL, NEMA, IEC, and many AHJs have expressed concern that the method and practice of removing KOs is very inconsistent among electricians. Even in instances where the manufacturers have claimed the KOs to be suitable for bonding and UL testing has supported those claims, problems can arise because of material stresses caused by removing the KOs.

There is far from universal agreement with respect to concentric KOs in general. however, your arguments focus on the NEC and you offer Mike Holt’s interpretation in support of your interpretation. That being the case, I’ll limit my comments to the NEC.

NEC 250.92B (2008 edition) states “Electrical continuity at service equipment, service raceways, and service conductor enclosures shall be ensured by one of the following methods:”

It goes on to say “Bonding jumpers meeting the other requirements of this article shall be used around concentric or eccentric knockouts that are punched or otherwise formed so as to impair the electrical connection to ground. Standard locknuts or bushings shall not be the sole means for the bonding required by this section.”

Notice the phrases “at service equipment” and “service conductor enclosures”.

Concluding that the NEC 250.92B does not apply in this instance would also require concluding that the panel on the left is not “service equipment” and that it is not a “service conductor enclosure”. Bill’s original message clearly suggests that this is service equipment. I based my comments on the presumption that the panel on the left was indeed a service panel. Obviously, I have no way to know.

It is my opinion, based on the facts presented and my interpretation of NEC 250.92B that the equipment is:

  • Service equipment and
  • That electrical continuity is required, and
  • The KOs are concentric and therefore,
  • Standard locknuts or bushings shall not be the sole means for the bonding

As I said at the beginning of this message, I sincerely respect your knowledge of the NEC and the electrical trade in general. I usually refrain from posting “me too” messages but I read your posts with interest and almost always agree with you.
I do not know you well but I suspect that you and I share a personality flaw. We cannot resist a debate. It is a great way to learn and to become better at what we do.

If you would like to continue this debate, please let’s do it in private. In depth NEC debates, in my opinion, serve little if any value on a home inspection message board. We should be here to help others, not to try to dazzle them with our knowledge.

I welcome any opportunity to engage in discussion with other electrical experts. My concern is for the way others on this board might interpret our public debates. While you and I may see it as friendly sparring, others may see it as bickering or outright hostility. We have seen this board change dramatically over the past few years. It feels less and less like a friendly place for inspectors to help each other. You, I, and several others here are obviously passionate about the electrical trades. I want to be sure that others understand that our way too detailed messages are all in the interest of helping each other, not to be chest-pounders.


I am sorry if my responses came across that way. I was truly not trying to start anything with you or even spuring a debate as trust me I am done with those days on this forum. I was simply trying to pull your view on the subject and nothing more and you have stated it. You are a good man and do alot for the members and thats what it is all about ( no chest pounding here…trust me ). It just happens to be my view the service bonding and over 250V are different issues than the load side conductors with ECC and CONCEN and with my conversations with the many manufactures I was a consultant to they ( They being the ECC and Concen.) are tested by the manufacturer for reliability on feeders and branch circuits was all I was driving at.

No worries from me fella and again I am not here to start any debates or the like, simply to give assistance when needed and to know when to shut up and fold into the background. You are good for the members and thats what counts.

I have found that in my 20+ years in this industry ( and BTW I am not an electrical engineer…thank GAWD ) that opinions of every kind are valuable and have merit and I would never wish to squash anyones opinion so please accept my appologies if you felt i was doing that as it was not my intention, only to help bring views to the front of the mind and nothing more.

The good news is being a municipal inspector and supervisor myself I learn the USBC, IBC and IRC which make reference to the NEC…so the funny side of that story is I had to learn the OTHER codes just to get permission for me to be an expert in the NEC since Virginia does not adopt the NEC as a whole. Gotta love the codes my friend…Now lets teach some folks.

Good post Paul. Thanks to you both for your replies.

What Bill said, excellent discussion gentlemen. :D:D:D:D