Changing conduit size in middle of run?

[Scott R]

I was confronted with the question of whether or not conduit runs could change size in the middle of the run. for example 1" PVC/GRC stubbs up from below ground and at approx 12" AFF a coupling is installed on the GRC threads then an 3/4 emt connector and 3/4 emt piping is continued from that point to a destination point. It looks like 300.10 or 300.12 would prohibit this from happening but not sure?

 

[Volta]

I was confronted with the question of whether or not conduit runs could change size in the middle of the run. for example 1" PVC/GRC stubbs up from below ground and at approx 12" AFF a coupling is installed on the GRC threads then an 3/4 emt connector and 3/4 emt piping is continued from that point to a destination point. It looks like 300.10 or 300.12 would prohibit this from happening but not sure?

I don't think the change in size is a violation, though in practice it can be very difficult to fish!

One might think of 310.15, second paragraph as disallowing a "box connector" for EMT to be installed into a threaded coupling for RMC. Not "designed and listed" for that purpose.

If the threads on the connector are not tapered, the 344.42(B) could be used as "running threads" may not be used on RMC couplings.

Welcome to the forum.

 

[stevenj76]

It is a really good idea to put a C condulet, when that 3/4 emt will continue on alot further. It really isn't that expensive, compared to the extra time trying to fish the pipe. But A+ on increasing your size on the PVC run underground!

 

[Cow]

I agree with using a C condulet or box.

I made the mistake of using reducer bushings one time in the middle of a run where it stubbed out of the floor and that's a mistake I won't make again.

 

[Jim W in Tampa]

I see no reason you can't do it but unless i have a box or t or something then i would think the run must be derated to smallest size unless under 2 feet

 

[LarryFine]

I made the mistake of using reducer bushings one time in the middle of a run where it stubbed out of the floor and that's a mistake I won't make again.

Yeah, it can be hard to feed a fishtape in from the wrong end. Reminds me of the kids' puzzler:

What can go up a chimney down, but can't go down a chimney up?

Hint: Think of dragging a Christmas tree through the woods the wrong way.

 

[3-D]

I see no reason you can't do it but unless i have a box or t or something then i would think the run must be derated to smallest size unless under 2 feet

Not sure I follow you, why would you have to derate the run because you downsized your conduit? So long as your conduit is still properly sized for the conductors and you haven't added any conductors, the rating should stay the same?