3 phase service

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sokkerdude

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I have a 1600 amp 3 phase 480 volt service for a mill plant. All my loads are 3 phase motors and one 45 KVA 120/208 transformer. There is no 277 V load at all. The utility company set a 1000 KVA Y transformer. My question is, do I need neutral in the service lateral. Inspector says yes, but I can not find it in the code. Please help.
 
sokkerdude said:
I have a 1600 amp 3 phase 480 volt service for a mill plant. All my loads are 3 phase motors and one 45 KVA 120/208 transformer. There is no 277 V load at all. The utility company set a 1000 KVA Y transformer. My question is, do I need neutral in the service lateral. Inspector says yes, but I can not find it in the code. Please help.
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If I remember right, and IMHO you need the service neutral to bond to the neutral in the transformer... but I cant remember a code section.
 
Check 250.24(C).

If the power company has grounded the transformer XO you will have to bring a neutral from that XO into the service disconnect.

If the power company has left XO isolated the NEC would not require you to bring a neutral in.

But are you looking to install an ungrounded system?
 
I am with Iwire { Bob } check that part very carefull and also verify with the POCO with netural if they did bond it or not.

I know mine POCO's in Wisconsin must have netural in wye system and ditto with France [ EDF ]

Not too often I heard a ungrounded Wye system if you go that route you have to run master RCD { GFI }

Merci,Marc
 
Check out 220.61 No freebees here, it requires you to dust off that calculator. I always run these kind of calcs by another engineer and the plant electricians as well. My best teachers are the mill electricians because of their years of knowledge and zero BS factor. (Plus if you run it by them they can't nail you later for not doing it right :)
 
Yeah look up in 220.61.

However there may have some addtional local code requirement that may change the figures a bit

The last time I did that figure it was 12.5% but I belive it do change now due I am used to French codes they figure it in 32% of phase conductors. { this is only with no load on netural conductors if have load the bet is off }

Merci,Marc
 
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