Conduit ID

Old 08-26-04, 07:06 PM
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Conduit ID

I was wondering if the 1/2", 3/4" and 1" conduit measurements are inner diameter or outer diameter?
Old 08-26-04, 07:44 PM
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It's inside diameter, but it's only a "trade size." The precise diameter varies with the type of conduit. So each of the dozen kinds of 1/2" conduit will have a slightly different inside diameter. The NEC has tables which give you the exact diameter based on the nominal diameter and the type of conduit.

For example, in 1/2" conduit, EMT is actually 0.622" inside diameter, ENT is 0.560", FMT is 0.635", IMC is 0.660", LFNC-B is 0.632", LFNC-A is 0.630", LFMC is 0.632", RMC is 0.532", Schedule 80 PVC is 0.526", Schedule 40 PVC is 0.602", PVC type A is 0.700", etc.

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