EV Chargers Service Calculation

[jimjones]

What size service I will need for 4 48amp ev chargers. It’s for an apartment complex. They will have a service of their own coming out of the pad transformer. If you don’t mind, please show calculation

 

[acrwc10]

What size service I will need for 4 48amp ev chargers. It’s for an apartment complex. They will have a service of their own coming out of the pad transformer. If you don’t mind, please show calculation

Sorry I have taken enough tests for one week. How about you do the calculations and share what you have come up with, then we will let you know if you are on the right track.

 

[jimjones]

I don’t even know where to start. I know How to do dwelling load calculation, but this is a little different

 

[tortuga]

What size service I will need for 4 48amp ev chargers../../. They will have a service of their own coming out of the pad transformer.

48 X 4 = 192A for service lateral
48 X 4 X 1.25 = 240A for service entrance conductors.

 

[jimjones]

But the are 125% for continuous load. Do I factor that in?

 

[jimjones]

Never mind I see it

 

[jimjones]

It’s like you’re adding up the breakers. How is this right. You won’t do that on a dwelling calculation

 

[jaggedben]

It’s like you’re adding up the breakers. How is this right. You won’t do that on a dwelling calculation

You said this service is just for the EV chargers, so it's not for a dwelling. Both per code and practically speaking in my opinion, for a service with only EV chargers there should be no demand factor. The optional calculations for dwellings assume everything won't be on at full load at once, but you can’t assume that here.

 

[Fred B]

220.57 Electric Vehicle Supply Equipment (EVSE) Load.
The EVSE load shall be calculated at either 7200 watts (volt-amperes) or the nameplate rating of the equipment, whichever is larger.

625.42 Rating.
The EVSE shall have sufficient rating to supply the load served. Electric vehicle charging loads shall be considered to be continuous loads for the purposes of this article. Service and feeder shall be sized in accordance with the product ratings, unless the overall rating of the installation can be limited through controls as permitted by 625.42(A) or (B).

220.53 Appliance Load — Dwelling Unit(s).
Applying a demand factor of 75 percent to the nameplate rating load of four or more appliances rated 1⁄4 hp or greater, or 500 watts or greater, that are fastened in place, and that are served by the same feeder or service in a one-family, two-family, or multifamily dwelling shall be permitted. This demand factor shall not apply to the following:
(5)Electric vehicle supply equipment (EVSE)

 

[suemarkp]

Is your supply single phase or 3 phase? That changes the amp size of the service. Also if 3 phase, it is best to do chargers in sets of 3, e.g. 3, 6, 9, 12... four wastes capacity.

 

[acin]

220.57 Electric Vehicle Supply Equipment (EVSE) Load.
The EVSE load shall be calculated at either 7200 watts (volt-amperes) or the nameplate rating of the equipment, whichever is larger.

625.42 Rating.
The EVSE shall have sufficient rating to supply the load served. Electric vehicle charging loads shall be considered to be continuous loads for the purposes of this article. Service and feeder shall be sized in accordance with the product ratings, unless the overall rating of the installation can be limited through controls as permitted by 625.42(A) or (B).

220.53 Appliance Load — Dwelling Unit(s).
Applying a demand factor of 75 percent to the nameplate rating load of four or more appliances rated 1⁄4 hp or greater, or 500 watts or greater, that are fastened in place, and that are served by the same feeder or service in a one-family, two-family, or multifamily dwelling shall be permitted. This demand factor shall not apply to the following:
(5)Electric vehicle supply equipment (EVSE)

this must be from 2023 nec

 

[letgomywago]

Is your supply single phase or 3 phase? That changes the amp size of the service. Also if 3 phase, it is best to do chargers in sets of 3, e.g. 3, 6, 9, 12... four wastes capacity.

If up to me I'd stick with a 320 single phase can with a couple 200a 8 space main breaker panels it would allow for a couple extra chargers if necessary in the future and be not much more expensive. When outdoor I get wary of maxing out panel rating with plug on breakers. Maybe if it was a bolt on it might be long enough lasting. If in a garage disregard my idea on the grounds of making the bus last so up sizing it.

 

[jimjones]

Is your supply single phase or 3 phase? That changes the amp size of the service. Also if 3 phase, it is best to do chargers in sets of 3, e.g. 3, 6, 9, 12... four wastes capacity.

Single phase

 

[jimjones]

this must be from 2023 nec

this must be from 2023 nec

Thanks!!

 

[jimjones]

If up to me I'd stick with a 320 single phase can with a couple 200a 8 space main breaker panels it would allow for a couple extra chargers if necessary in the future and be not much more expensive. When outdoor I get wary of maxing out panel rating with plug on breakers. Maybe if it was a bolt on it might be long enough lasting. If in a garage disregard my idea on the grounds of making the bus last so up sizing it.

That’s make sense. Good answer and thank you for your response.

 

[jimjones]

Change of plans guys. The apartment complex has 120/208 3 phase because of the elevators in the buildings. Do my figurings change because of the 3 phase transformer?

 

[letgomywago]

yes it changes it if you decide to do a 3 phase panel.

My recommendation is a 3 phase 200a bolt on it'll come at a premium in cost so if you're trying to be cheap as possible then a plug on panel board would work too. Even with this it might be cheaper to still do a 320 1 phase can with 2 200a 3r panels.

4 chargers would put 96a on one phase and 48 on the other 2. You can calculate total VA but since it's imbalanced you need to account for this. I'd still do a 200a service to this no way I'd do smaller it won't be cost effective to be smaller.

If doing 3phase order the panelboard with breakers and all and price it out between your 3 or 4 big name manufacturers supply houses in the area. Don't piece meal it.

 

[suemarkp]

Three 48A single phase 208V loads on a 3 phase panel will not be 48A per phase -- they add to each other by a factor of 1.73 or so. This is easiest to see when you use VA as a calculation: 48*208 = 10KW. Three 10KW loads is 30KW. 30KW on a 3 phase panel, evenly balanced, is 30000/208/1.732 = 84A. But since there are 4 chargers, two legs are going to have an additional 48A load. So the panel needs to support 84+48 = 132A * 125% = 165A (168A * 125% = 210A if you want to support 6 chargers).

Question: do the chargers still draw 48A if fed with a 208V supply?

 

[letgomywago]

Three 48A single phase 208V loads on a 3 phase panel will not be 48A per phase -- they add to each other by a factor of 1.73 or so. This is easiest to see when you use VA as a calculation: 48*208 = 10KW. Three 10KW loads is 30KW. 30KW on a 3 phase panel, evenly balanced, is 30000/208/1.732 = 84A. But since there are 4 chargers, two legs are going to have an additional 48A load. So the panel needs to support 84+48 = 132A * 125% = 165A (168A * 125% = 210A if you want to support 6 chargers).

Question: do the chargers still draw 48A if fed with a 208V supply?

Yep I forgot to do square root of 2 in mine.

Most of the cars will charge anywhere between 200v to 240v so that they can be sold internationally. The voltage will provide less charging speed but will charge at same amperage.

 

[brycenesbitt]

Change of plans guys. The apartment complex has 120/208 3 phase because of the elevators in the buildings. Do my figurings change because of the 3 phase transformer?

Know that in the nearish future, the J3400 connector will allow 277V charging: specifically for 3-phase.
Which cars will be compatible is an open question....