Transformer Secondary Neutral

[garyvigrass]

Feeding a 480v 3ph subpanel with no neutral. Then 2 branch circuits from
480v subpanel to 2 transformers 480v to 120/208v. To feed 2-120/208v
subpanels. Is this legal with NEC? I think it is according to Art 450.5 A.
Can someone confirm this is the right Article.
Thank You.

 

[charlie b]

450.5 addresses "auto transformers." You are not dealing with those, so you have the wrong article. That said, I do not know what you are specifically trying to ask. Is "what" legal? If you are asking if you can start with a panel that has no neutral, and feed two transformers that will have neutrals on their secondaries, that is as common as anything gets. It is simply a delta-wye transformer, and you end up with "separately derived systems." The grounding arrangements for these animals are described in 250.30.

Welcome to the forum.

 

[skeshesh]

Charles is correct. Feeding 480-120/208Y delta-wye to distribute power to panelboards is a very common practice. Make sure you read through the grounding requirements for the secondary in article 250 for proper installation.

 

[kacper]

450.5 addresses "auto transformers." You are not dealing with those, so you have the wrong article. That said, I do not know what you are specifically trying to ask. Is "what" legal? If you are asking if you can start with a panel that has no neutral, and feed two transformers that will have neutrals on their secondaries, that is as common as anything gets. It is simply a delta-wye transformer, and you end up with "separately derived systems." The grounding arrangements for these animals are described in 250.30.

Welcome to the forum.

Charlie is absolutely right. You also need to adjust the max. rating of OCPD
based on the table Table 450.3(B)