277/480v Service Question

Status
Not open for further replies.
A

AJBelectric

Member
Location
Westchester, NY
Hi All,

New to to the forum so bare with me if this question has been addressed in some form.

I have recently been asked to complete a 277/480v 3phase 225a service. The service is fed
from a 400a MDP approximately 1500' away from the new panel location. I am picking up where the previous electric a contractor left off- he pulled 4 conductors to the location thinking that the service requirement was only single phase. Conductors are sized properly to account for voltage drop.

My question is: Can I wire the panel with 3 hot legs and a ground, and no neutral? All loads from this panel will be 3-phase equipment that won't require a neutral. And if a step-down 120/208 transformer is needed down the road, I should be able to feed it with 480v and a ground. Pulling in an additional conductor is not an option.

I have asked all my local inspectors but each seem to have a different opinion and no definitive solutions.

Any feedback is appreciated. Sorry for the long-winded post.

AJ
 
Yes you can have a feeder that is strictly 3 phase with no neutral. Of course as you stated you may need a trany later
 
The OP mentioned the word "service" in a context which was not entirely clear.

If the three phase comes from a wye source with a grounded neutral, then the code seems to require that the neutral conductor be brought as far as the first disconnect even if no connected loads will be using the neutral.

If that is the case, the answer to the OP may depend on just what, if anything, is upstream of the panel he is going to install.
 
GoldDigger said:
The OP mentioned the word "service" in a context which was not entirely clear.

If the three phase comes from a wye source with a grounded neutral, then the code seems to require that the neutral conductor be brought as far as the first disconnect even if no connected loads will be using the neutral.
Click to expand...

The OP is using incorrect terminology.

The service is fed
from a 400a MDP approximately 1500' away from the new panel location.
Click to expand...
He is describing a feeder but if it were a service I agree with you.

Roger
 
If the wiring method is metal raceway that can be the equipment grounding conductor and you still have a conductor that can be used for neutral. Many like to pull a wire type EGC anymore but the raceway is still NEC compliant.
 
Thanks for the Reply guys.

Roger - absolutely correct in my using of the wrong terminology. I am talking about a panel downstream from my main service disconnect.

kwired - raceway is PVC or else I would most definitely use this method.

This was extremely helpful guys, thank you for the feedback. Look forward to further discussions with you. Great forum.

AJ
 
Status
Not open for further replies.
Top