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I'm guessing the answer is "no" but I saw this question and got curious. If panel fillers are expensive, and you don't have a breaker, can you 3d print your own? I'm guessing the panel front cover and fillers are part of UL and therefore making your own is against code?

Sam
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  • Interesting idea; what would the approximate cost be to print that? I'll let someone else answer if it's technically a code violation, but since its only job is to keep stray fingers out of the panel, and a DIY one would do that just fine, I'd expect most inspectors would be fine with it regardless. Especially if it's an older panel where the proper part is almost impossible to find. – Nate S. Jan 06 '21 at 17:33
  • @NateS. that's the rub... cost in materials? $0.30 or so. Cost in design and manufacture? depends on how much you value your time, how much you like to do 3d modeling and how you feel about learning. – Sam Jan 06 '21 at 17:39
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    Yeah, for a one-off it seems like it might not be all that worth it, but if someone were able to model a bunch of specialty parts and then put a small 3d printer in the truck instead of trying to stock all of them or always needing to make a special trip to get one, I could see how that could be extremely useful. – Nate S. Jan 06 '21 at 17:44

4 Answers4

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One more step

You'll need to send several specimens of your 3D-printed cover plate to Underwriter's Laboratories along with a $5000 check, and have them "UL-Classified" for the panel in question. You'll be able to 3D-print the "UL-Classified" mark on the cover plate once you have that certification.

What UL will do is give it a variety of tests to make sure it won't accelerate a fire and will actually contain a panel fire, which is its primary job; will hold up to prodding by a 5-year-old who wants to see what's inside the magic box; won't go brittle and fail over time (least; they'll bomb it with UV light), and if forced to burn by an externally applied fire, won't off-gas toxic gases of some kind.

Harper - Reinstate Monica
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You need to provide protection "substantially equivalent to the wall of the equipment..."

The governing NEC requirement for loadcenter "blank space" filler plates is in NEC 110.12(A):

(A) Unused Openings. Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, or those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to the wall of the equipment. Where metallic plugs or plates are used with nonmetallic enclosures, they shall be recessed at least 6 mm (¼ in.) from the outer surface of the enclosure.

...which is much easier for a DIY to provide with sheet metal

This points us to what the wall of the equipment is required to provide, and that, in turn, is set out by NEC 312.10(B):

(B) Strength. The design and construction of enclosures within the scope of this article shall be such as to secure ample strength and rigidity. If constructed of sheet steel, the metal thickness shall not be less than 1.35 mm (0.053 in.) uncoated.

So, I'd use a piece of 16 gauge (or 1.6mm thick) sheet steel painted to match the existing cabinet, fastened with Garvin GSSTs (these are fairly short 10-32 self-drillers) in suitable places, as my "blank plate" if you couldn't find a manufacturer identified blank/filler and plugging the opening with breakers wasn't an option.

ThreePhaseEel
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  • Why wouldn't ABS be strong enough? – Mast Jan 07 '21 at 12:27
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    @Mast -- ABS would probably be mechanically strong enough but the issue is what happens if a fault starts making a mess inside the box – ThreePhaseEel Jan 07 '21 at 12:43
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    @Mast, notably ABS could fail to provide protection (it could melt or burn) in case of an electrical fire, but sheet metal would hold up. There are some specifically fire retardant filaments. Possibly they would work, but that would take more research. – BillThePlatypus Jan 07 '21 at 15:06
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    @BillThePlatypus It would require a really expensive printer to print a filament that was melt-resistant at a reasonable temperature. There are printers that can print metal, and services that will print items for you so you don't have to own one, but even just printing with them is the opposite of cheap. – user3067860 Jan 07 '21 at 16:15
  • Not disputing the logic of this answer, but the QOFP from Square D made for their own steel panels is plastic. – StayOnTarget Feb 29 '24 at 00:17
  • @StayOnTarget -- yeah, it's plastic that has to go through UL rating tests though, likely V-0 rated as per UL94 even. that's a tough row to hoe for most printers -- there's only a handful of V-0 blue cards in the UL database, and they're all for specific filaments combined with specific professional-grade 3D printers – ThreePhaseEel Feb 29 '24 at 03:13
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The plastic fillers are not expensive--about $1.50. I have a big box of them but if you can’t find one a breaker is only a few dollars. Could you print one? It would not be listed but would be better than screwing or gluing a metal or plastic plate over openings I have seen both and inspectors have mentioned them but not failed inspections. On the screwed one I told the inspector I was afraid to pull it as the hole down the center strap would not leave much metal there he agreed to leave it and the glued another inspector told the home owner he probably wasted more on epoxy than the blocks cost.

I would say printing them would cost more than they cost but as far as filling the holes I have not had inspectors flag solid home made covers. They will flag duct tape in a heartbeat. I had one home owner that objected to me plugging he said the tape would be fine and the inspector wrote it up and required another inspection that is an expensive decision.

isherwood
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Ed Beal
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  • Another bonus of fitting spare breakers is that OP would have spare breakers in the future that match their box and the style of the existing ones. – Criggie Jan 07 '21 at 18:43
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3D printers come in a bunch of different varieties. There are some that are able to print rocket parts. But your typical home/workshop/small commercial 3D printer is printing plastic. By melting it. Guess what: If your printer can melt it to print with it, sparks/fire inside a panel could melt it. Which would not be a good thing.

A piece of sheet metal cut down to size and screwed into the panel cover with a screw on each end would do the job just fine. It also would only take a few minute to make & install (assuming you had some source material on hand - e.g., a piece of leftover ductwork).

That would not meet UL specifications, so an inspector could reject it, but it would get the job done. But I wouldn't trust any plastic unless it was appropriately tested/certified because not all plastics are the same, and some could be quite dangerous if things go bad.

manassehkatz-Moving 2 Codidact
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    There are printers capable of printing plastic to UL94 V-0 flame retardant specifications, but that requires specifically formulated filaments and apparently specific printing hardware as well (the Ultimaker S5 can do it, and so can some of the bigger Stratasys models, but those are the only FDM 3D printers that have done Blue Card printing) – ThreePhaseEel Jan 07 '21 at 00:36
  • The newer oem blocks I have are low temp plastic the old ones are Bakelite and I know there are 3 different styles in my bucket and none except the oldest have any marking at all. – Ed Beal Jan 07 '21 at 01:24