Legality of shop made electrical boxes
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  1. #1
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    Default Legality of shop made electrical boxes

    Electrical equipment is expensive, and sometimes hard to get. Or we just needed something we couldn't get quickly. As a result we have made a variety of custom electrical boxes ranging from slim oversized boxes to big bulbous LBs that let the 400mcm wire loop around nicely.

    My question is if we were to make more such equipment (and it was otherwise to code regarding dimensions and volume and protection) would we be able to have out shop made parts installed by a licensed electrician in a permitted project without issue? It's typically brake formed bolt together 1/8" aluminum with all press in threaded inserts, and does look professional.

    I mostly started thinking about this when pricing out wire gutter. I can make longer sections, with IMO better couplers. I far prefer drilling holes in aluminum to using steel knockouts, so that's not an issue. I'm seeing $15 per foot at the low end for 6x6 wire gutter, where it would cost $5-$12 to build depending on material thickness (1/8" aluminum is overkill). Large LBs and other boxes have far more cost savings.

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    The problem with self made electrical enclosures is you cut out the electricians profit on the items,and most electricians refuse to use them citing various excuses ,such as non compliance,lack of code markings etc......find a sparky who is happy to use them ,and your OK.

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    There are various standards that must be met such as NEMA, CSA and UL. Your enclosures would have to be approved for whatever type (wrt liquid tightness, dust ingress etc.) you’re looking to emulate.

    It’s more than just getting an electrician to agree to install them. If you burn a building down you can be sure the insurance co will find out who manufactured the enclosure should the fire be proven to originate within it.

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    I have never seen aluminum boxes, always steel.

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    The real question is not whether you can find an electrician who will use them, but if the local building code "AHJ" (authority having jurisdiction, usually a city or country building department, the folks who issue work permits and inspect the work) will accept them. For simplicity, most agencies require a UL stamp on things. If it's a brand they recognize, they don't go looking for the stamp. If it's something new to the inspector, he/she may want to see it.

    I suspect things would go much smoother if you approached the AHJ before starting the project where you want to use shop-made boxes, and worked out what would be satisfactory to them (and got it in writing).

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    Yeah, that was kind of what I was figuring. I didn't mention this is all inside works, joined up with EMT. I think boxes are typically steel for cost reasons. It would be pretty tough to make boxes with sharper edges, worse size knockouts, and more gaps than conventionally available stuff from the hardware store.

    It would be especially convenient when building sheet metal welding booths where I'm already cutting 30 sheets and bending profiles, so I may as well cut a few more and run very little EMT.

    I can probably still get away with it but it would be extremely convenient to make a long channel with holes for outlets and breakers that functions as wire gutter for everything.

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    NOT allowed in the NEC, no ul label...But it has been done more than once, would probably fly if you were the end user and the installer, but in Calif with union electricians, no bet...Phil

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    Check in the wiring methods in the latter half of Chapter 3 to see whether what you're building is required to be listed. Wireways, auxiliary gutters, etc. Check 312 and 314 to see if your boxes and conduit bodies need to be listed.

    IIRC minimum metallic box wall thickness is 1/16" or thereabouts. Look for "Construction requirements".

    Powder coated or galvanized steel is going to be the ticket. Never seen an aluminum electrical enclosure other than die-cast conduit bodies - and those ones turn nasty when exposed to moisture. Aluminum *anything* just doesn't really have a good track record in the electrical industry, lol. Well... aside from TMCX connectors and MC cable I suppose.

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    Quote Originally Posted by Just a Sparky View Post
    Check in the wiring methods in the latter half of Chapter 3 to see whether what you're building is required to be listed. Wireways, auxiliary gutters, etc. Check 312 and 314 to see if your boxes and conduit bodies need to be listed.

    IIRC minimum metallic box wall thickness is 1/16" or thereabouts. Look for "Construction requirements".

    Powder coated or galvanized steel is going to be the ticket. Never seen an aluminum electrical enclosure other than die-cast conduit bodies - and those ones turn nasty when exposed to moisture. Aluminum *anything* just doesn't really have a good track record in the electrical industry, lol. Well... aside from TMCX connectors and MC cable I suppose.
    Reading through those sections now. Interestingly, there are a lot of additional requirements for ferromagnetic raceways to make sure they don't heat up from induction.

    Looking at conventional aluminum electrical equipment, I can agree about not wanting it. Thin walls, enormous grain structure (no idea what alloy these are cast from) and terrible coating are all going to kill it, expecially outdoors. Indoors I don't see much issue.

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    Quote Originally Posted by Strostkovy View Post
    Reading through those sections now. Interestingly, there are a lot of additional requirements for ferromagnetic raceways to make sure they don't heat up from induction.
    Mainly just normal grouping of circuit conductors and some specific provisions to allow big isolated-phase services and feeders for reasons of practicality. All par for the course really. All conductors have to enter via the same knockout or the steel has to get notched between the two, can't be supported by metallic strut with metallic straps, no steel pipes, etc. No closed circuits around any of the isolated phases and minimizing the distance between them is what it amounts to.

    I've heard tell of metal strut-straps and strut glowing red hot from such a mistake.



    Outside of that the only place you really encounter un-grouped circuit conductors is with PV arrays - and those are DC.

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    Article 314.4 contained the most interesting info

    I see the minimum thickness for steel is 0.059 and cast aluminum is 3/32". It's allowable to go thinner if tested and listed. Metallic materials other than specified must be at least 1/8".

    They must be coated inside and out (Many commercial conduit bodies aren't)

    It mentions sheet metal boxes over 100 cubic inches must be made of sheet metal at least 0.059 thick and constructed to be adequately rigid. No mention of sheet metal type.

    I don't know about wire gutter, but I *think* for boxes over 100 cubic inches (coated and with a grounding point) I am in the clear. Specifically galvanizing and enameling are called for, with special restrictions if enamel is the only corrosion prevention. It seems coatings are a separate article.

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    Using what I learned I was able to come up with better searches. Wire gutters don't seem to need to be listed as long as they are made properly. Same with boxes.

    However, the authority having jurisdiction may only accept UL listed items on everything. I doubt that's the case here, but if I have any projects coming up I will certainly ask them.

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    Also worth checking the customer's specs too. Sometimes they specify 100% American-made, no zinc fittings, no aluminum, everything piped, etc. Very conceivable they might specify everything has to be listed - especially on a job big enough to need long lengths of metal wireway.

    Also note that wireways and gutters are basically the same equipment being used in different capacities. One article might mention something that the other doesn't require.

    Bottom line, whatever you do make sure you're building above code, not pinching pennies. The code is merely the bare-ass minimum to provide basic safeguarding against things burning, shocking and 'sploding.

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    Quote Originally Posted by Just a Sparky View Post
    Also worth checking the customer's specs too. Sometimes they specify 100% American-made, no zinc fittings, no aluminum, everything piped, etc. Very conceivable they might specify everything has to be listed - especially on a job big enough to need long lengths of metal wireway.

    Also note that wireways and gutters are basically the same equipment being used in different capacities. One article might mention something that the other doesn't require.

    Bottom line, whatever you do make sure you're building above code, not pinching pennies. The code is merely the bare-ass minimum to provide basic safeguarding against things burning, shocking and 'sploding.
    Oh, in this context it would be for our own shop. Being able to put in all of the wireway/gutter up front before equipment in the future would be massive to allowing us to add equipment with ease. I have no doubt that what we build is as good as or better as what is commonly sold for the application, but legality isn't always about that.

    We currently have to keep spending a weekend running another 200-300 amp feeder to another panel pretty much every time we want to put anything in. The conduit is installed cleanly but the sheer amount of it offsetting around conduit that's offsetting around conduit and poking from a panel in weird locations because it's all that's left, etc. etc.. This building had 1 and a half (12 spaces barely counts) warehouse panels and now it has 5. It's just so much work constantly. I actually came up with a trick to cut out and reroute sections of conduit with minimal time and material loss, up to code of course. Replacing 100 feet of 3/4 EMT or offsetting 2" EMT around it were both unpleasant options.

    I'm honestly just day dreaming at this point. It will be a while until we feasibly outgrow this building. But an open concrete tilt up warehouse with high ceilings and a metal roof, wire gutter all around, and an elevated catwalk for accessing air/water/electrical in a neat layout all around the walls of the building are my dream shop.

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    Talking to most of the 'pros' here, if you even touch a piece of copper that might possibly contain electrons, you've broken about a dozen 'laws' and will go to NEC jail for at least ten years.

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    Quote Originally Posted by moonlight machine View Post
    I have never seen aluminum boxes, always steel.
    Outdoor "bell boxes" are all aluminum (cast), with aluminum covers.

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    Sounds like what you need is an overhead plug-on busway or two. They hang well below existing pipes. Put a machine in? Plug in a bus plug and drop to the machine. Take out or move a machine? Remove the bus plug and drop for later use somewhere else.

    De-energized of course. Big busways fed right off the gear have lots of available fault current and are protected by big breakers with relatively long clearing times. Wouldn't be fun to find out the stabs are misaligned when you try to plug in live.






    Also worth mentioning as someone did above, the legality of doing your own work inside of your own commercial shop is questionable depending on the state you're in. At least around here, IIRC you need a signatory master electrician on your payroll to perform in-house electrical work in lieu of a licensed, bonded and insured contractor.

    There are a lot of moving parts when it comes to electricity and if you don't deal with the technicalities on a daily basis it's easy to screw up something serious. E.G. selective coordination, equipment short-circuit current ratings, OCPD interrupting ratings, available fault current calculations, arc energy labeling requirements, temperature and current-carrying conductor de-ratings, acceptable usage of flexible cords and cables... Proper grounding and bonding is probably the most frequent screw-up, especially with flexible conduits and cables as well as 'hard' pipes entering through concentric/eccentric knockouts.




    Also a fun watch:

    https://youtu.be/AFlBLQjOAJI?t=120

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    If you don't mind the initial investment cost, buss duct is a pretty slick way to go, and there is lots of it on the surplus market.

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    I spent 19 years working for Milbank.

    Milbank - Quality Metering, Enclosed Controls and Enclosures

    I designed and built most of their heavy stamping dies that produced almost all of their enclosures.

    All of these ran 16 gage galvanized steel, and .059 gage aluminum. All boxes were powder coated using their custom built coating lines.

    We constructed our own U.L. lab and had is certified by them. It is still being used to this day.

    If you do have your own ISO documentation and have access to a U.L. lab, you can have your boxes documented and approved for sale to anyone.

    Of course you will need to carry liability insurance on you products as well. This will increase the cost considerably.

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    A note on surplus busway - it is very important to inspect any used busway very closely for damage and clean it out if necessary, as care is not always taken when demolishing it. One good dent or loose screw in the wrong place is all it takes. Definitely bring out the Megger and test every piece - and again with the plug and feeder disconnects open after the installation is complete.

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