Derating a neutral

[dhsvcs]

When is it legal to derate a neutral on a commercial 3 phase service with a 120/240 v 3 phase high leg system ?

 

[LarryFine]

When is it legal to derate a neutral on a commercial 3 phase service with a 120/240 v 3 phase high leg system ?

Any time you can calculate the greatest possible neutral current; typically based on the greater 120v loads on one phase.

 

[dkidd]

When is it legal to derate a neutral on a commercial 3 phase service with a 120/240 v 3 phase high leg system ?

That is covered in

220.61 Feeder or Service Neutral Load.

 

[dhsvcs]

Thanx....read the section and am applying it to a job I'm working on now...( setting up the plans / as builts ) before seeing my P.E. )