NEC 300.20 and 376.20 explained?

[Netserk]

We are working at a factory and they have a Solar installation. They are using a step down transformer to bring the 480 down to 208. There are 3-3 in. EMT pipes running along the wall to the exterior disconnect. Each pipe contains 3x 350 Kcmil wires and a ground. It appears to me that they each pipe only contains one phase. 3 runs of phase A in top pipe, 3 runs of phase b in bottom pipe, and 3 runs of phase c in bottom pipe. Am I misunderstanding the code or is this really BAD!?

 

[Netserk]

We are working at a factory and they have a Solar installation. They are using a step down transformer to bring the 480 down to 208. There are 3-3 in. EMT pipes running along the wall to the exterior disconnect. Each pipe contains 3x 350 Kcmil wires and a ground. It appears to me that they each pipe only contains one phase. 3 runs of phase A in top pipe, 3 runs of phase b in bottom pipe, and 3 runs of phase c in bottom pipe. Am I misunderstanding the code or is this really BAD!?

Sorry that was 3 runs of phase B in the middle pipe

 

[LarryFine]

Welcome to the forum.

Yes, it's bad, especially in metallic conduit.

 

[electrofelon]

Oops

 

[don_resqcapt19]

If the conductors are loaded anywhere near their ampacity I would expect the conduit to get very warm.

 

[jaggedben]

If the conductors are loaded anywhere near their ampacity I would expect the conduit to get very warm.

On a PV system they will be, on a sunny summer day.

 

[Netserk]

Actually you'll get more on a cool autumn noon

 

[wwhitney]

Would be OK if the EMT were aluminum and the provisions of 300.20(B) were satisfied.

Cheers, Wayne

 

[don_resqcapt19]

Would be OK if the EMT were aluminum and the provisions of 300.20(B) were satisfied.

Cheers, Wayne

I say it is, but the code making panel does not agree. I had a PI to delete the exception 300.3(B)(1), because 300.3(B)(3) permits that in all locations, not just underground. The CMP said you can only do in per the exception.

 

[wwhitney]

I say it is, but the code making panel does not agree.

If the CMP intends 300.3(B)(3) to apply only to cable type wiring methods, they need the change the text. The current text clearly applies to all wiring methods, so the CMP is mistaken.

Cheers, Wayne

 

[don_resqcapt19]

If the CMP intends 300.3(B)(3) to apply only to cable type wiring methods, they need the change the text. The current text clearly applies to all wiring methods, so the CMP is mistaken.

Cheers, Wayne

The panel statement indicates that they believe that 300.3(B)(3) does not really apply anywhere

3-11 Log #2229 NEC-P03 Final Action: Reject
(300.3(B)(1) Exception)
____________________________________________________________
Submitter: Donald A. Ganiere, Ottawa, IL
Recommendation: Delete the following:
Exception: Conductors installed in nonmetallic raceways run underground shall be permitted to be arranged as isolated phase installations. The raceways shall be installed in close proximity, and the conductors shall comply with the
provisions of 300.20(B).
Substantiation: The exception is not required. Such installations are permitted by 300.3(B)(3) in all locations, not just underground locations.
Panel Meeting Action: Reject
Panel Statement: This exception is necessary to permit installations where nonmetallic raceways are installed in close proximity with all of Phase A in one raceway, all of Phase B in another raceway, all of Phase C in another, and all the grounded conductors in another raceway. Where this is useful is betweewunderground manholes so the phase conductors can exit the raceways and be easily racked within the manhole, taking up less space, and making it easier to do testing and maintenance on the installation. This would not be permissible without this exception.
Number Eligible to Vote: 13
Ballot Results: Affirmative: 13