Number of Conductors in a Conduit

kwired

Electron manager
Location
NE Nebraska
Yes this is underground, But the Power Company code book says the following:

"Three-phase secondary cables shall be phase grouped in the case ofconcrete ducts and HDPE conduits ( Phase A, B,C and neutral in thesame conduits) and shall be phase isolated in the case of steel conduits(Phase A, B,C and neutral in separate conduits)."

Let me know your thoughts
If you do that with ferrous raceways, there will be heating effects on the raceways, and higher overall impedance in your conductors. You want one of each phase and neutral where used in each raceway so that their opposing magnetic fields cancel one another and has less heating issues on the ferrous raceway.

Brass, stainless, aluminum or non metallic conduits aren't a problem - they are non magnetic.
 
Why is your neutral full size for solar?
The code is such that the inverter needs to state that the neutral is for voltage reference only. Some do and some dont. I have actually never seen a reduced neutral, even though most of the systems I have,seen and worked on use inverters that state the neutral is for reference only. Its a rediculous waste IMO.
 

pv_n00b

Senior Member
Location
CA, USA
Thanks everyone for your information. It was really helpful. Since I am running 6 sets of A,B,C and N and using Steel Conduit, my Power Company requires the conductors to be phase isolated in the case of steel conduits(Phase A, B,C and neutral in separate conduits). So I am running 4 conduits.

Utilities do not have to comply with the NEC. If these conductors fall under utility control then you follow their rules, if they fall under the NEC then you follow the NEC. If the utility wants to apply utility rules to NEC systems then you have a problem.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
Utility rule or not I would not do it. I have a engineer friend who had a huge issue with this in Durham, NC... He was called in to see what the trouble was and it didn't take long before he saw the problem. The conduits were incredibly hot which was causing problems with the terminals, etc.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
I don't know if anyone has posted the section but here it is.

300.3(B)(1) Paralleled Installations. Conductors shall be permitted tobe run in parallel in accordance with the provisions of
310.10(H). The requirement to run all circuit conductors
within the same raceway, auxiliary gutter, cable tray, trench,
cable, or cord shall apply separately to each portion of the
paralleled installation, and the equipment grounding conductors
shall comply with the provisions of 250.122. Parallel runs
in cable tray shall comply with the provisions of 392.20(C).


Exception: Conductors installed in nonmetallic raceways run underground
shall be permitted to be arranged as isolated phase, neutral,
and grounded conductor installations. The raceways shall be installed
in close proximity, and the isolated phase, neutral, and grounded
conductors shall comply with the provisions of 300.20(B).
 

chicagosparky

Member
Location
Chicago, IL
What's the length of the run? If it is under 100 feet, then no big deal. but if it's longer than 100', trying to pull 7 or 9 conductors in one raceway becomes "troublesome".
 

TheElectrician

Senior Member
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