PVC use indoors

[Carultch]

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.

 

[kwired]

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.