follow up EV charger questions

J

jdping2

Member
Location
Monterey ca
Recent thread that I posted was answered and I would like to thank all for the comments received, Owner has sticker shock and is now asking for a revised proposal which means more calc's that dont know how to formulate. here goes - Owner now wants 6 EV chargers for Step vans ( looks like UPS truck), Owner has 480 volts available 200 amp spare breaker in 277/490 switchboard. I have 6 chargers which draw 80 amps max at 208 volt single phase . I now need to deliver a 480 feeder, size a transformer and size a 120/208 panelboard which will ultimately accept the 6 new 2 pole 100 amp breakers ( per charging manufacturer). Owner does not want to build in any flexiblility or additional amperage capacity for future car chargers- he simply wants a panel that will handle the full load of chargers and nothing more. How many amps will be required at new 120/208 panelboard? What size is transformer ? How many amps is main breaker ( owner does understand that existing 480 volt main breaker might need to be re-sized.

thank you to the entire community for the support
 
C

CoolWill

Senior Member
Location
Alabama
Occupation
Electrical Contractor
I'm no calculations expert when it comes to EVs, and I'm kinda lazy so I don't want to get a code book, but wouldn't you just get your total watts: 80 x 208 x 6 x 1.25 = 124800 W and then use that? That's like 350 amps at 208 three phase and 150 amps at 480 three phase. Use a 150 kVA transformer for a little overhead.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Here's mine: 80 x 208 = 16,640va x 6 = 99,840va = 99.84 kva

What will it take to be able to deliver 100va at 208v and at 480v?

I get 277.57a and 120.28a respectively. Add your 25% to those.
 
W

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
As a transformer's rating is continuous, the required transformer rating is only 6 * 208V * 80A = 99,840 VA, so a 100 kVA 3 phase transformer would suffice.

Agree on the secondary and primary OCPD sizes for non-100% rated OCPD.

Also, if these are regular J1772 EVSEs, then you have the option to use a 240V delta secondary. The vehicles would charge a little faster if provided 80A @ 240V, although that would obviously require a larger transformer.

Cheers, Wayne
 
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