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Transformer tap changer

Question asked by apurvadave on May 10, 2020
Latest reply on May 21, 2020 by wf1029

I have small storage room which has 75kVA transformer 480V to 208/120V three phase with tap changer primary side.  The transformer secondary feeds Panel A in the same room.  

The Panel A feeds receptacles, heaters, and area site light.  Site light one branch circuit is 600 feet and second branch circuit is 400 feet.  In order to avoid voltage drop tap changer is being used.  It would elevate secondary more than 208V which panelboard sees and other circuits in panelboard see. It’s not problem for site lights due voltage drop however panelboard, receptacles and heaters would see higher nominal voltage.  Does NEC 2014 elevate of nominal voltage secondary above nominal voltage of panelboard is rated for, receptacles, heaters?