Usage of drainage tubes for electric cables
Usage of drainage tubes for electric cables
(OP)
Hello,
Is it possible to use normal drainga tubes (PVC or uPVC i do not know for sure) to run electric cables carrying a couple of hundred amps? The size of the ducts allow the code requirement of 60% space, but what about dielectric strength and if it is accessible then why are there corrugated ducts that seem to be exclusive for electrical cables?
Thanks.
Is it possible to use normal drainga tubes (PVC or uPVC i do not know for sure) to run electric cables carrying a couple of hundred amps? The size of the ducts allow the code requirement of 60% space, but what about dielectric strength and if it is accessible then why are there corrugated ducts that seem to be exclusive for electrical cables?
Thanks.






RE: Usage of drainage tubes for electric cables
RE: Usage of drainage tubes for electric cables
PVC conduit is rated for the use of conductors at elevated temperature. Fittings are different than pipe fittings. Elbow radii for conduits are designed for pulling conductors. Materials and testing standards are altogether different. Most electrical codes, inspectors and insurance companies require electrical raceways be listed and approved for electrical use (in the U.S. that would commoly be by Underwriters Laboratories).
Can it be made to work? Yes. I have seen it. Is it recommended? No.
RE: Usage of drainage tubes for electric cables
I have 4 ducts and i must run 3 phases and neutral to the load.
The neutral and each phase are 4 conductors.
The qustion is, which is the best configuration:
A] Duct 1: 4 conductors of phase A, Duct 2: 4 conductors of phase B, duct 3: 4 conductors of pahse C, duct 4: 4 conductors of neutral + earthing conductor.
or
B] Duct 1: {A1, B1, C1, N1}, Duct 2: {A2, B2, C2, N2}, Duct 3: {A3, B3, C3 ,N3}, Duct 4: {A4, B4, C3, N4, PE}
?
RE: Usage of drainage tubes for electric cables
Configuration A will increase impedance (and voltage drop), result in unbalanced phase impedances (and unbalanced currents), and if the cable is shielded, increase shield circulating current.
See comments on NEC 310.4, Conductors in Parallel, in the NEC Handbook.
RE: Usage of drainage tubes for electric cables
I did not understand this in NEC 310.4
"Conductors of one phase, polarity, neutral, or grounded circuit conductor shall not be required to have the same physical characteristics as those of another phase, polarity, neutral, or grounded circuit conductor to achieve balance."
This note has been added in the 2005 edition, could you please explain in 2 words?
RE: Usage of drainage tubes for electric cables
Your option A could work if there is no ferrous metal that would surround one or more ducts but not all. If there is ferrous metal around part of the total number of conductors you will have severe heating problems.