Isolated Phases in UG Conduits

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priorityded

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Can someone clarify Art. 300.5(I) Exception 2 for me?
Does it mean that, in PVC installed underground, each phase, grounded conductor and grounding conductor for a 3PH4W&G service can be run in (5) separate conduits, based on 300.3(B)(1), 300.20(B),310.4 & 250.122?
 
Re: Isolated Phases in UG Conduits

priorityded said:
Can someone clarify Art. 300.5(I) Exception 2 for me?
Does it mean that, in PVC installed underground, each phase, grounded conductor and grounding conductor for a 3PH4W&G service can be run in (5) separate conduits, based on 300.3(B)(1), 300.20(B),310.4 & 250.122?
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Yes, but if it enters a ferrous enclosure than slots would be required to be cut between the conduit entries.
 
Here is the Article:

300.20 Induced Currents in Metal Enclosures or Metal Raceways.
(A) Conductors Grouped Together. Where conductors carrying alternating current are installed in metal enclosures or metal raceways, they shall be arranged so as to avoid heating the surrounding metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together.
Exception No. 1: Equipment grounding conductors for certain existing installations shall be permitted to be installed separate from their associated circuit conductors where run in accordance with the provisions of 250.130(C).
Exception No. 2: A single conductor shall be permitted to be installed in a ferromagnetic enclosure and used for skin-effect heating in accordance with the provisions of 426.42 and 427.47.
(B) Individual Conductors. Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.
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Understood. That would be 300.20(B).
I'm particularly interested in the grounding conductors, based on what it says in 310.4, which does not mention grounding conductors.
 
I am curious as to what application you want to use this for that has EGCs?

I have used this in the past but only for service conductors.
 
Bob, Trevor.....I am totally lost and confused on this cutting holes and slots. :? If I pull into a trouffer,etc......?
 
iwire said:
I am curious as to what application you want to use this for that has EGCs?

I have used this in the past but only for service conductors.
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I was wondering about this also. The OP mentions a "3PH4W&G service".

Why would a service entrance have a grounding conductor?

And as Bob has mentioned in the past, it is much easier to shape in multiple sets of conductors when they are separated by phase. The mess of criss-crossing conductors can usually be reduced or eliminated.
 
Shame on me for using the word "service". Here's what I've got. I'm trying to get a customer out of a messy situation. The design calls for a relocation of the building service to an outdoor lineup. The intent was to intercept the existing underground utillity secondaries and re-route them in and out of the new outdoor service switch. The exisiting indoor gear will now be considered a sub-panel, and bonding will now be at the new service location. However, as we all know, there are no GEC's present in the secondary service conductors. Since they will now be classified as feeders, there must be GEC's. There is a spare conduit of equal size to the other four PVC conduits. All conductors are the same size, in this case 600kCMIL. I want to re-terminate & re-identify all phase and neutral conductors in an isolated fashion (separate conduits for each phase & N) and add the GEC's (per 250.122) in the spare conduit.
Thanks for any help with this.
 
triphase said:
Bob, Trevor.....I am totally lost and confused on this cutting holes and slots. :? If I pull into a trouffer,etc......?
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Greg, buy cutting slots between each entrance the inductive heating associated with the EMF is negated, think single current carrying conductor in a ferrous conduit or raceway.

Priorityded, per the "pure" wording of 250.122(F) each raceway would have to have an EGC IMO :(

Also IMO, I don't see a problem in the installation you describe, but MO won't hold much weight in a debate with your inspector or AHJ either.


Roger
 
Don - I can't use 250.32(B)(2) because the new service is GF protected.
Roger - Check 300.5(I) Exception 2 vs 250.122(F). The exception mentions EGC's and EBC's. Sorry, but what are IMO & MO?
Thanks
DED
 
Ded, IMO is In My Opinion and MO would be My Opinion. You will see IMHO at times also which would be In My Humble Opinion.

Considering 300.5(I) EX 2, I would see this as allowing your installation. :)

Roger
 
DED it sounds like you may have found a solution. 8)

I recommend you try to determine if the raceways are entirely PVC, if there are RMC sweeps used the isolated phase arraignment is not the way to go.

I imagine you would have quite a hot spot if there are metal sweeps in the runs.
 
Bob - You make an excellent point. This could be a problem, since the underground is over 100LF and stubs up under the building slab.
Ouch. Thanks for all the help.
DED
 
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