I am installing a 480 volt feeder that requires 4-600 MCM per phase. At the top of our MCC if I route through a aluminum plate can I route all A phase through the same hole or do I need to route A/B/C through the same penetration hole?
I am installing a 480 volt feeder that requires 4-600 MCM per phase. At the top of our MCC if I route through a aluminum plate can I route all A phase through the same hole or do I need to route A/B/C through the same penetration hole?
Why can't I use the provisions of 300.3(B)(3) for that application?No, you can only do that underground with PVC or with single conductor MI.
You are correct. It is imperative that you route all three phases through the same hole. If you don't the single phase will create a hysteresous magnetic field to occur in the metal around that phase. This will cause a transformer action in the metal which results in a current flow. Because the metal is a very poor conductor it will get hotter than a pistol when current flows through that phase. The more current, the more heat. By routing all 3 phases through the same opening the resultant magnetic field is cancel led out to zero. The only way that you can route a single phase though a single opening is if the material which surrounds the conductor is non magnetic. Often a rectangular opening is cut and a piece of glasstic is fastened in its place and the openings are made in the glasstic.
Why can't I use the provisions of 300.3(B)(3) for that application?
The OP stated aluminum. That is not ferromagnetic, but would still conduct eddy currents given the chance.
Hysteresis heating is the result of the behavior of a ferromagnetic material in a varying magnetic field and is not an issue here.
,But even if a non-conductive material is used or a slot is cut, there is still a question of how the paralleled phase feeders got to the outside of the panel and how they will be secured in the opening if they are not in a raceway.
I don't doubt it.I have a few other stories that defy all fact reason and logic.
I am still lost, can you tell us how the conductors are getting to the MCC?
Even if these are say single conductors installed in cable tray, I can't see why you'd cut 3 or 4 holes. One hole (or slot) would suffice for all 12 plus any EGC's. Besides that, the conductors should be arranged in A/B/C sets in the tray anyway. He'd have to criss-cross them to get each phase in a separate hole.I am still lost, can you tell us how the conductors are getting to the MCC?
The OP stated in post #1 that the conductors will route through an aluminum (non-ferrous) plate on the the top of the MCC.
Even if these are say single conductors installed in cable tray, I can't see why you'd cut 3 or 4 holes. One hole (or slot) would suffice for all 12 plus any EGC's. Besides that, the conductors should be arranged in A/B/C sets in the tray anyway. He'd have to criss-cross them to get each phase in a separate hole.
+1The OP stated in post #1 that the conductors will route through an aluminum (non-ferrous) plate on the the top of the MCC. Non-ferrous materials are not highly susceptible to induced current heating.
The conductors would need to be phase grouped as complete individual sets of ABCN/G in any given raceway, which could be a problem for the OP.
Informational Note: Because aluminum is not a magnetic metal, there will be no heating due to hysteresis; however, induced currents will be present. They will not be of sufficient magnitude to require grouping of conductors or special treatment in passing conductors through aluminum wall sections.
The feeder conductors are 600 mcm 4 per phase routed from a 480 volt switchgear via a cable tray. The switchgear and MCC are in the same building. The connections for the feeder cables at the MCC are located at the top of the MCC in a top hat enclosure provided by the MCC manufacturer. Take a look at the attached picture. My question is are we okay with routing of cable as shown? Thanks again.....
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Just curious, why does the "B" phase have additional busbar material?