Parallel Conductors

[xformer]

Hello,
with an install of running parallel conductors in phased conduits underground, When does one have to be concerned with inductive heating in the surrounding metal in the a concrete duct bank?

 

[ron]

I always worry about it so I do phase isolated ducts very infrequently.

Depending on the current going through the feeder, the inductive heating will radiate out from the ductbank inches to feet I would imagine.

Do they really need ferrous metal near the duct bank?

 

[JoeStillman]

I never understood the point of phased conduits. Your inductive reactance goes way up.

 

[ron]

I never understood the point of phased conduits. Your inductive reactance goes way up.

I'm sure the installation becomes more straight forward not having to mix, dress and re-dress the phases into their proper termination groupings. Most folks don't care about inductive reactance (or even care what it means)

 

[xformer]

I always worry about it so I do phase isolated ducts very infrequently.

Depending on the current going through the feeder, the inductive heating will radiate out from the ductbank inches to feet I would imagine.

Do they really need ferrous metal near the duct bank?

IMHO phased conduits make for a much cleaner and neater install and for places where power continuity is important I would think this would be a better install method due to the fact that if two conductors fault in the same conduit, power is maintained.

 

[Dennis Alwon]

IMHO phased conduits make for a much cleaner and neater install and for places where power continuity is important I would think this would be a better install method due to the fact that if two conductors fault in the same conduit, power is maintained.

Iwire used to have a great picture that showed 12 pvc conduits coming in underground to a Main switchgear each with the phase conductors in it. It was clear that the phase A conduits being under the phase A lugs, etc made for a much neater install

 

[kwired]

I never understood the point of phased conduits. Your inductive reactance goes way up.

Three large conduits (with all same phase within) vs three large conductors with similar grouping won't give you somewhat similar results? You want to keep close proximity between raceways. If only three raceways (plus a neutral where necessary) put them so they are as close as possible in trench they act like one big cable to some extent.

 

[Tony S]

Iwire used to have a great picture that showed 12 pvc conduits coming in underground to a Main switchgear each with the phase conductors in it. It was clear that the phase A conduits being under the phase A lugs, etc made for a much neater install

This one?

 

[LarryFine]

Are those PVC conduits bonded?

 

[Dennis Alwon]

This one?

View attachment 22882

Maybe but I thought there were more conduits in a wider area. I may be mistaken but you get the idea. I am pretty sure the other pic had the terminals parallel with the opening and thus was much wider....It would be more obvious in a wider setup

 

[kwired]

Are those PVC conduits bonded?

PVC cement bonds the fittings to the conduit:happyyes:

 

[LarryFine]

PVC cement bonds the fittings to the conduit:happyyes:

 

[Wire-Smith]

you can use fiber reinforced concrete rather than steel

 

[don_resqcapt19]

Hello,
with an install of running parallel conductors in phased conduits underground, When does one have to be concerned with inductive heating in the surrounding metal in the a concrete duct bank?

As long as the steel does not pass between the conduits, it is not an issue.