[Alex422]

I have a question about the following. I always install a 3 phase sub-panel off of a 3 phase main panel. One company on a job I recently went to installed a single phase sub off of the 3 phase main. Is this against any NEC codes or is it normal practice? I understand the AIC ratings and how they pertain, but I am just curious how this (or is not) acceptable. Load balancing could become a major issue in this circumstance.

Any thoughts?

 

[Pete m.]

I can't think of any NEC restriction.

Pete

 

[micromind]

There's nothing in the NEC that would prohibit it, but unless there's a very good reason, the first thing I think of when I see this is 'what sort of a hack would do such a thing?'

It's pretty common to have a 120/208 3ø service to an apartment building and each unit has a single phase panel, but other than that, I can't think of a good reason to do it.

Other than to be cheap........

 

[LGLS]

There's nothing in the NEC that would prohibit it, but unless there's a very good reason, the first thing I think of when I see this is 'what sort of a hack would do such a thing?'

It's pretty common to have a 120/208 3ø service to an apartment building and each unit has a single phase panel, but other than that, I can't think of a good reason to do it.

Other than to be cheap........

Depending on the size and type of sub, have you compared prices of 3ø panels to single phase?

 

[ablyss]

Hi Alex, excellent question. Got my wheels spinning early this morning!

You are absolutely right about the load balancing and in good judgment to be concerned. In almost all cases this scenario would be discouraged. The reason it is allowed is because under properly engineered electrical systems the bottom line is cost effective. The NEC may one day address this but as for future revisions on how is beyond me.

Thanks