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I am feeding a 480 delta- 208/120 wye transformer from a 480 wye source. Is there a code article that would require a neutral to be pulled with the phase conductors to the transformer?
 

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I am feeding a 480 delta- 208/120 wye transformer from a 480 wye source. Is there a code article that would require a neutral to be pulled with the phase conductors to the transformer?
That I remember I never did. Your 3 phase 480 volt is the feed and on the secondary you DERIVE your neutral, if needed to the load.
 

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I did not think the transformer needed it, but thought I might be missing a code requirement to pull it. I understand that I will be deriving a neutral on the transformer.
 

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No neutral on the primary side.

Yes neutral on the secondary side.
As long as it is a delta wye which I would think 99% of transformers in a commercial establishments (excluding buck boost).
 

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The funny thing is, it's the norm for us to derive a noodle, where the poco's will often run a solid noodle thru to us .....~CS~
 

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I did not think the transformer needed it, but thought I might be missing a code requirement to pull it. I understand that I will be deriving a neutral on the transformer.
A delta - wye transformer will not need a neutral on the supply and only needs a neutral on the load side if you want to.

A wye - wye transformer would require a neutral on the supply side and only needs a neutral on the load side if you want to.
 

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Discussion Starter #10
BBQ said:
A delta - wye transformer will not need a neutral on the supply and only needs a neutral on the load side if you want to. A wye - wye transformer would require a neutral on the supply side and only needs a neutral on the load side if you want to.
No problem feeding 480 delta transformer from 480 wye service- correct?
 

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Which begs the question, when would a wye primary transformer be required?
Why wye? Wye primaries are often used on large substation class transformers. 1 reason is the closer you get to the star point the lower your voltage is to ground therefore requiring less insulation and the windings can be closer to the transformer can. Another reason is that by having the neutral it gives you more options for your protective relaying of the transformer. Wyes also handle unbalanced loads better which for all these reasons that pretty much all utility generators are wye connected.
 

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Honestly said:
Which begs the question, when would a wye primary transformer be required?
I once saw a wye to wye transformer used in an inverter setup on a solar array we installed. I don't know what its purpose was or reason for being wye was though.
 
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