Neutral conductor required for 3ph 4w service from dedicated transformer?

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McCES

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OHIO
I have an industrial project that is all 3ph loads - no single phase loads. The utility supplies the primary side of a 2500kva xfmr with a 480V 3ph secondary with the center grounded at the xfmr.
The initial design is to run parallel phase conductors but no neutral since we have no single phase loads. Is this acceptable? I'm considering this a separately derived source because of the xfmr 250.20(D).
If it does not qualify as a separately derived source then I presume 250.25(C) applies and I have to run the neutral per Table 250.102(c)(1).
Do I need a neutral bus in the switchgear? It looks like 250.25(C) says I just need a neutral terminal.
 

McCES

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Location
OHIO
Since there are no single phase loads do I need a neutral bus in the switchgear, or just a termination point for the neutral and the bonding jumper?
 

GoldDigger

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Placerville, CA, USA
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Retired PV System Designer
When you say that the utility supplies the primary and you connect to the secondary, and you call it a service in your thread title, does this mean that the service point from the utility is on the secondary side and therefore your first disconnect is literally the service disconnect?

As long as the neutral is terminated there, I do not see the code as requiring a neutral bus for branch connection, but in the service disconnect the GES and the neutral will be bonded together anyway, so one bus would serve both purposes as long as it has enough wire terminations.
 

augie47

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Location
Tennessee
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State Electrical Inspector (Retired)
Since there are no single phase loads do I need a neutral bus in the switchgear, or just a termination point for the neutral and the bonding jumper?

230.66 requires your service equipment be listed and 408.3(C) requires the main bonding jumper, etc., and 230.75 requires a 'neutral disconnect link'. When the manufacturer supplies a piece of listed service equipment the design pretty much address all those issues,.
 
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