3 Phase 3 wire convert to 3 Phase 4 wire

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ericgold

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On a job I'm currently working, there is a 200 amp panel being fed by 3 3/0 conductors which are powering various HVAC equipment. The owner wants to add some single phase equipment in and the EC proposed running an additional 1 inch conduit to the panel with a new 3/0 for a neutral.

I'm not a licensed electrician myself, but have worked as an apprentice (before I got into CCTV/Communications), and I remember a similar situation occurring and that being a violation. Is what the EC is proposing code compliant?
 

chris kennedy

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Miami Fla.
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60 yr old tool twisting electrician
Violation.

300.3 Conductors.
(B) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).
 

augie47

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Since the E/C is discussing running a conduit for the neutral, he could, of course, run the conduit and install a complete circuit for the equipment requiring a neutral (being "single phase" does not necessarily mean a neutral is required)
The cost of that vs a transformer would help make the decision.
 
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charlie b

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I infer from your description that the feeder to the 200 amp panel has a neutral. If so, then the EC should just run a couple new branch circuits from that panel. Since he suggested installing a one inch conduit, he could get at least four branch circuits in that conduit. You can get up to nine circuits, if you share neutrals. So the EC's suggestion is not the best approach, even if we disregard the code violation.

Just out of curiosity, where did the EC propose to land the new neutral wire, once it was pulled to the vicinity of the load? How did the EC propose to connect the single phase loads?
 

infinity

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New Jersey
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Sounds like he will install a neutral bar in the 3 phase, 3 wire panel to land his neutrals. He wants to run the feeder neutral in a separate conduit back to where the existing 3 phase, 3 wire feeder originates. Depending on what that equipment is there may be no provisions for 120 voltage circuits.
 

ericgold

Member
I infer from your description that the feeder to the 200 amp panel has a neutral. If so, then the EC should just run a couple new branch circuits from that panel. Since he suggested installing a one inch conduit, he could get at least four branch circuits in that conduit. You can get up to nine circuits, if you share neutrals. So the EC's suggestion is not the best approach, even if we disregard the code violation.

Just out of curiosity, where did the EC propose to land the new neutral wire, once it was pulled to the vicinity of the load? How did the EC propose to connect the single phase loads?


The 200 amp disconnect in the basement has a neutral from the POCO, he proposed running an additional conduit from the disconnect to the panel and powering the single phase equipment from that panel.

I'm thinking the only way to properly (and cheaply) due this is run brand new conduit, pull the lines from the existing conduit and run the old line + 1 new line in the new conduit. Or perhaps put a junction box near the disconnect, and splice into 1 phase conductor and the neutral, and install a smaller panel off that?
 

infinity

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So you have a 200 amp disconnect with 3 phase, 4 wire feeder to it. From there you have a 3 phase, 3 wire feeder that you want to change to a 3 phase, 4 wire feeder. There are several ways you do this. One as you suggested install a panel right next to the 200 disconnect and run your 120 volt branch circuits out from there or set a transformer at the end of the 3 wire feeder. The one thing you cannot do is run the neutral in a separate conduit.
 

ericgold

Member
Could anyone point me to which type of transformer the EC would need to accomplish this? The load would be no more than 2 refrigerators and a possible light circuit. I want to present this as an option to the owner and EC.
 
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