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Thread: PVC use indoors

  1. #21
    Join Date
    May 2013
    Location
    Massachusetts
    Posts
    2,215
    Quote Originally Posted by kwired View Post
    3/4 PVC can be up to 3 feet from box to first support as a general rule, and every 3 feet afterward.
    Is there any particular reason why the distance limit from termination to the first support is 3 ft across the board for ALL non-flexible circular raceways, whereas the span limit is a function of type and trade size?

    I would think that for conduits requiring spans smaller than 10 ft, the distance limit to the first support would shrink proportionately to the allowable span. For instance, with a 5 ft is the span limit, I would expect to see 1.5 ft as the distance limit to the first support. Cantilevers are generally between 30% and 40% of beam spans, for the same structural performance, so I would think a similar concept would apply to the structural integrity conduit systems.

  2. #22
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    32,914
    Quote Originally Posted by Carultch View Post
    Is there any particular reason why the distance limit from termination to the first support is 3 ft across the board for ALL non-flexible circular raceways, whereas the span limit is a function of type and trade size?

    I would think that for conduits requiring spans smaller than 10 ft, the distance limit to the first support would shrink proportionately to the allowable span. For instance, with a 5 ft is the span limit, I would expect to see 1.5 ft as the distance limit to the first support. Cantilevers are generally between 30% and 40% of beam spans, for the same structural performance, so I would think a similar concept would apply to the structural integrity conduit systems.
    No idea where they come up with those distances, same for the 1 foot to first support for most flexible raceways, which is sometimes difficult to comply with, when maybe 2 feet would still seem pretty reasonable.

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