PVC to RMC and back to PVC

[Michele]

Hello to the Forum.
An electrical contractor is installing underground ductbanks, that transition to above ground. A design drawing indicates to utilize RMC for the conduit sweeps. The intention of the note was to run Schedule 80 PVC horizontally and transition to RMC for the stub up to above grade.
The contractor transitioned all elbows to RMC, even the horizonal elbows in the ductbank.
The installation is straight-horizontal PVC to RMC horizontal elbows, to straight-horizontal PVC, to an RMC vertical stub up.
As we could correct the note to be more specific, the question is this: Is there a concern for pulling the cable from PVC to RMC, to PVC to RMC?
Some ductbanks are completed with concrete encasements. The un-poured ductbanks could be corrected if recommended.
Is there a concern for the cable pull to transition as mentioned, if the correct fittings are installed and do not create and exposed edge concern at the elbow fittings.

 

[ptonsparky]

Some types of pull rope will cut thru a PVC sweep in short order. From personal experience, you only do it once.

Take care that the internal diameter of the Sched 80 is beveled at each transition. Esp important when fill is at maximum and with smaller raceways.

 

[busman]

Some types of pull rope will cut thru a PVC sweep in short order. From personal experience, you only do it once.

Take care that the internal diameter of the Sched 80 is beveled at each transition. Esp important when fill is at maximum and with smaller raceways.

If you burn thru PVC that is in concrete, would you even know? I've burned ONE elbow; lesson learned.

Mark

 

[busman]

Hello to the Forum.
An electrical contractor is installing underground ductbanks, that transition to above ground. A design drawing indicates to utilize RMC for the conduit sweeps. The intention of the note was to run Schedule 80 PVC horizontally and transition to RMC for the stub up to above grade.
The contractor transitioned all elbows to RMC, even the horizonal elbows in the ductbank.
The installation is straight-horizontal PVC to RMC horizontal elbows, to straight-horizontal PVC, to an RMC vertical stub up.
As we could correct the note to be more specific, the question is this: Is there a concern for pulling the cable from PVC to RMC, to PVC to RMC?
Some ductbanks are completed with concrete encasements. The un-poured ductbanks could be corrected if recommended.
Is there a concern for the cable pull to transition as mentioned, if the correct fittings are installed and do not create and exposed edge concern at the elbow fittings.

250.86 Exception 3 would allow this, as long as the horizontal elbows are in 2" of concrete.

Mark

 

[roger]

I agree with the others. The EC may be doing the horizontals for his own benefit regardless of specs.

 

[Michele]

Thank you all for the great responses. I recall the vertical sweeps should transition from PVC to RMC due to pulling concerns so it does make sense to have a large radius sweep as a horizonal elbow. As you mentioned, as long as there is not a concern with the difference in internal diameters. Thank you again for your assistance.

 

[ptonsparky]

There is a concern about internal diameters if the 80 is too small.

 

[letgomywago]

Just Throwing this out there. Fiberglass 90s with pvc coupling ends are available and depending on how many there are it might be cheaper and for sure is quicker

 

[ptonsparky]

Just Throwing this out there. Fiberglass 90s with pvc coupling ends are available and depending on how many there are it might be cheaper and for sure is quicker

IDK about cheaper but certainly easier to work with.

 

[Fred B]

How are you bonding the intermediate Ridged that is set between two non metallic pieces of conduit?

 

[roger]

How are you bonding the intermediate Ridged that is set between two non metallic pieces of conduit?

Probably not necessary in a duct bank, see Exception #3 in 250.86

 

[kwired]

IDK about cheaper but certainly easier to work with.

material may be more labor will be less, need to consider end result.