It is a trick question. There have been twenty responses, so far, and only one correct answer is essentially correct. I don’t usually get involved in find-the-problem threads but I couldn’t resist this one.
The pictures are not needed to determine the answers. However, the answer is confirmed by the first picture. Read the question carefully.
The enclosures all appear to be NEMA 1, which are not suitable for outdoor use. NEMA 3R is usually the minimum acceptable enclosure type for outdoor use.
This is the reason for the question. If they are outside circuits then the use of one neutral is acceptable as long as everything else is code compliant. The type of enclosures is what made me question the installation.
Mike,
I agree. It was a good question. Based on the photos and information provided, it appears to be an indoor installation. The presence of multiple NEMA1 enclosures suggests an indoor installation, not an outdoor installation. This illustrates why Section 13.2.3.1 of the code is so important (sorry but, I couldn’t resist ).
I mentioned the enclosures being NEMA 1 only for the benefit of those who may not have known that the NEMA 1 are not suitable for outdoor use. The enclosures are only one of several problems with the installation.
So far, it seems that only one person read the question carefully enough to focus on the real problem. Granted, I too have digressed with my comment about the enclosures but, as I said, the pictures are not necessary to understand the problem. The question, as Jeff presented it, is a trick question. The answer is in the question.
I actually had difficulty posing the question without giving the answer, but then there would not have been enough info to make a good guess. 
These boxes were all mounted inside a 48"x48" exterior-rated (double door) cabinet, similar to what I have posted below. The entire installation was wall mounted on the exterior of the residence.
Right. Without any information, the discussion might have gone in a completely different direction. The 120V statement is really the key to problem. Juan nailed it. The 120V statement and the MWBC statement are mutually exclusive. That’s why I called it a trick question. The key is knowing that a MWBC, by definition, has to have two or more ungrounded conductors that have a potential between them.
As I’ve said before, I usually don’t like to get into the really basic stuff because I don’t have much to add. For home inspectors, this is a good exercise in a more advanced concept that they are likely to see often.
There are two unusual features of the installation. One is the fact that the panel is only 120V. It would have been more practical for the installer to have made it a 240V panel.
The other unsual feature is the NEMA 1 enclosures within another outdoor enclosure. The large enclosures, by the way, look like they are probably NEMA 12. Also, by the way, my “code” comment may have come across as insolent. It was not my intent to be mean-spirited. That’s just my off-beat sense of humor. It was, however, an actual code reference.
NFPA 921 Section 13.2.3.1 states, in part,
“The small subject is first photographed from a distant position, where it is shown in context with its surroundings. Additional photographs are taken increasingly closer until the subject is the focus of the entire frame.”
My point in mentioning codes in home inspector discussion forums is not to get inspectors to look at codes. An inspector who mentions any code in an inspection is unnecessarily putting himself in jeopardy. This is especially true with electrical codes. All too often, people, including electricians, become so focused on the National Electrical Code that they make major blunders. The corpora of electrical standards is vast and interconnected. The NEC, in particular, either hands off to another standard or is silent on many important elements. Engineers, inspectors and so on are left to make decisions on information that either does not exist or that they do not always have ready access to.
Having trained hundreds of electrical inspectors, contractors and engineers, I have an idea of how certain things are commonly handled these professionals. As an example, there was a thread on this board recently in which I was challenged regarding load calculations. Someone said my comments were, in effect, invalid because the NEC does not address assigning a load value to receptacles in residences. This is a perfect example of a little knowledge being dangerous. The majority of inspectors I have worked with will use one of standards that exists for another type installation and apply it where the standard is not clear or does not exist.
To further illustrate my concern over home inspectors and others who are not specifically professionals in the electrical field citing codes, it is worth noting that the NEC does not adequately cover color codes. There are other electrical codes, including other NFPA electrical codes, however that do. A good electrician will carry that knowledge into areas where it has not been codified.
The ONE COLOR that EVERYONE needs to be aware of is YELLOW. Yellow is reserved for conductors that can remain energized while all service to a panel is OFF. Unfortunately, the apprenticeships for residential electricians are typically only two years and they do not go very deep into the trade. Consequently, residential electricians will often use wire colors willy-nilly. To be safe, Yellow should always be handled as though it is energized. Doing a spot-check is not enough. It could be de-energized one minute and energized the next minute without warning.
This is yet another example of how a qualified electrician will carry his knowledge of electrical codes other than the NEC into residential wiring. To a qualified electrician who has served a four-year apprenticeship, colors such as red, blue, yellow, orange and brown (there is not universal agreement over orange and brown) all have specific meanings. Even though they are not specifically required in residential, they are not going to stop following standard convention just because it is a residence.
I have known of many jurisdictions where the local inspection authorities enforce color codes, load demands and lots of other stuff inspite of the fact that the NEC does not specifically apply these things to residential wiring. Not knowing the signifigance of Yellow wire is a good example of how not only can a little knowledge can be dangerous, in could be fatal.
George, could you expand on yellow being a reserved color? Where is this spelled out?
Yellow seems to be the switched hot color in the Chicago area.
Thanks George you wealth of knowledge and ways of teaching are next to none and I want to thank you for always keeping it easy to understand by not using terms that only Master Electricians would now.
Point taken about the YELLOW wire and no use of CODE in reports are what are needed on this MB.
Proper pictures in context also so we can see what is going on is always better than hundreds of words.
Jim,
I am not going to cite or debate codes for a couple of reasons. Those reasons have nothing at all to do with you so please don’t take any of my comments personally. I have a very strong opinion with respect to discussing electrical codes on public forums, especially home inspector forums. The problem is that a little knowledge is dangerous. I am not in any way suggesting that that applies to you or anyone else who participates on this board. I have investigated many failures of electrical systems that had been wired in compliance with the NEC. Far too many electricians spend too much time memorizing the NEC without taking the time to understand how electricity and electrical systems work.
Color codes exist in a variety of electrical codes and standards. Most are in agreement but not all are. In the U.S. the standard for yellow has remained unchanged more than 50 years. There is some confusion in the trades because of long standing regional practices and, in part, because of the influence of IEC standards. Right now, I’d say that the biggest problems are with brown, orange, light blue and gray.
The following is from A national electrical code (NOT the NEC). I will not cite the specific code. Please note that I did not copy and paste the following. I have tried to type everything using the exact capitalization and punctuation that appears in the code. I also did not type the number of the IEC code reference. Everything in dark red is exactly as it appears in the code:
Note The international and European standards require the use of the color ORANGE for this purpose. (See IEC xxx-x for specific requirements.)
I will add that yellow conductos are almost always 120VAC. Brown is often used for low Voltage (15V or less) but it is also used for phase identification. Orange is also commonly used for phase identification. Gray is now commonly used grounded conductors because many people did not understand that “natural gray” is not gray at all. It is a yellowish off-white. The color was used to describe the color of natural rubber, which has not been used for many years. Gray was used for years for ungrounded conductors. Historically, blue has been used for DC in the U.S. but the IEC uses light blue for grounded conductors and dark blue for ungrounded.
There are reasons for a home inspector having some knowledge of what have historically been non-residential wiring methods:
I used to train apprentice electricians many years ago. Consistently, the ones that became the best electricians were the ones who were always asking why things are done as they are. Consistently, the ones who became the worst electricians were the ones who always wanted a code reference but didn’t ask “why”. They always wanted to know “how”. Of course, an electrician has to know how to do things too but I’d take an electrician who knows why over one who knows how any day.
To this day, when I teach NEC classes, I start by telling the attendees that we are going things a little differently. Their licenses require that they have a certain amount of time in code updates. The requirements, however, do not dictate how many topics have to be covered. We choose a small number of topics that we discuss in great detail. We might spend two hours talking about a single NEC requirement. When we leave, we all have a solid understanding of the concepts involved. I also tell my groups that even though I have been working in the electrical industry for a long time, I don’t know everything. Everyone participates. We all learn from each other.
A topic that is of particular interest to home inspectors is the connection of two or more conductors under a single screw. The seriousness the condition is not the same in all installations. I’ve done electrical classes for electricians and for home inspectors where we have had two hours of discussion just on that one topic. When we are done, an inspector will have a much better idea of how serious the problem is. Building codes are the lowest common denominator. Doing something according to a building code does not necessarily result in a good installation. Also, codes are not perfect. If they were, they wouldn’t have to be updated so often. A good building professional will be at least one or two steps ahead of building codes.
George,
What does all of this have to do with a residential panel installation and why the secrecy on the sources?
The source is for industrial control wiring. The branch circuits and feeders that supply the controller will still have to conform to the NEC and the colors outlined in 110.15, 200.6, and 250.118. Orange, white and gray, and green.
There are also differences in the European color codes.