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Thread: Class 2 Wiring in Concrete Outdoor Furniture

  1. #1
    Join Date
    Nov 2018
    Pittsburgh, PA

    Class 2 Wiring in Concrete Outdoor Furniture


    This is my first post here so I figured I'd give you a little bit of background on myself before I get to my question. I'm a mechanical engineer from Pittsburgh, PA who recently moved from a position in the automotive industry to working as part of a design team within the outdoor furniture industry. One of my first tasks here is to work with the designers on a piece of outdoor concrete furniture with integrated LEDs. The company I work for makes a range of lighted outdoor products, but this is the first in the concrete product line. Also, I noticed there is a low-voltage section of the forum, but my question is also code-related, so I hope this is in the correct place... please let me know if not.

    My question surrounds the wiring method, and what is acceptable/desired. I had initially planned on casting in LFNC and running our wiring through that, but we are very limited on space, and I have some confusion regarding whether or not we are allowed to encase 90deg connectors in concrete (2017 NFPA 70 356.42). If I cannot encase a 90deg connector, that method won't work. Because of our lack of space, the question of casting a CL2 cable directly into the concrete has come up, but I have not found a CL2 cable specifically rated for concrete encasement, and I'm hesitant to go this route for a number of reasons. The third option would be to fabricate a complex metal enclosure that would meet our space requirements and include a "conduit" for the wiring, and the whole unit could be placed in the mold during the concrete pour. I really like this idea, primarily from a manufacturing standpoint, but I'm not sure if it's going to fly when it comes to the code.

    My questions are somewhat general. Since I am new to this field and NFPA 70, is there any specific article that I should do more research on? Does anyone here have any sort of similar experience or insight into what is "commonly" done? Do any of these methods seem like a terrible idea on the face of it?

    Also, the product will undergo ETL testing, and I do need to reach out to our contact at the testing lab to get their feedback, but figured I would introduce myself and bounce some ideas off of this forum first. Please excuse any ignorance here, I'm much more familiar with SAE Standards than the NEC!! But I'm willing to learn and looking forward to hearing your feedback. Thanks in advance!


  2. #2
    Join Date
    Feb 2003
    Seattle, WA
    This thread was temporarily closed while the moderators discussed whether it was in keeping with forum rules. The consensus was that the thread is allowable. So I am now reopening it. I apologize to the OP for the delay and inconvenience.
    Charles E. Beck, P.E., Seattle
    Comments based on 2017 NEC unless otherwise noted.

  3. #3
    Join Date
    May 2018
    Jamaica and london
    since it is reopened I would use Outlet boxes/ junction boxes that are plastic and waterproof, and pvc conduit for the electrics, placing them before casting... the wires can be run after casting... Otherwise would use buriable cables if can find them in correct sizes...
    Student of electrical codes. Please Take others advice first.

  4. #4
    Join Date
    Apr 2009
    Williamsburg, VA
    You can encase in concrete a ltfnc 90-degree connector like a sweep, but not a lb.

    The cable type is more relevant than the wiring method. For example, nonmetallic and underground feeder cable cannot be directly encased in concrete per 334.12 A9, uses not permitted.

    Though I think it is a colossally bad idea, I think one could use say CAT5 or coax in concrete provided the manufacturer's instructions did not specifically exclude direct burial in concrete. You could use MC cable that is rated for direct burial.

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    Electricians do it until it Hertz!

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