Utility transformer secondary LTC to get 240 V from 277V

[boshbosh43]

Coming across an issue, we have installed a level 2 (AC) EV charger, and input AC voltage setup selected was 277V ( retrieving a phase to neutral ) from the Utility Transformer 480V. Yesterday we found that the charger is set up for 240/208 V.

I am aware that we will most likely have to install a step down transformer 277 à 240 V, but could we install a LTC ( Load Tap Changer ) on the Utility transformer secondary winding ( on one phase only) tapping that 277V to 240 V , that way we won’t have any discrepancy or making any demolition and re-work the entire installation/wiring? In such a way that it won’t violate the NEC code?
Thanks

 

[Elect117]

LTCs that I know of move all the phases. I don't know of a LTC that could modify the voltage by more than 5%.

Modifying the service in such a way can negatively impact everything else on it.

Trying to wire the device in such a way will definitely violate the manufacturer's instructions / warranty.

 

[tortuga]

( on one phase only) tapping that 277V to 240 V

I doubt you can get away with that on one, if the EV load is the only thing on the bank you change all three so you have a 416Y/240 service.

 

[hillbilly1]

Most likely the ground fault protection in the controller would not like it. Better off biting the bullet, and using a 120/240 step down transformer.