Specs for 240v outlet/breaker

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Newbie here, wife is about to by a used 2018 Leaf. I'm a little confused about the Level2 charging. Nissan says that using an L2-EVSE charging cable, it will charge the 40kwh version in 8 hours, which is a net of 5000 watts. But they also say you need to install a 50amp/240v outlet. That's 12000watts. I understand that outlets (over-current protection devices, specifically) need to be oversized, and that there's some inefficiency in the charging circuit. Still 12000watts versus 5000watts seems a bit extreme. Against code even, as breakers aren't supposed to be drastically larger than the expected load (I forget what the factor is, but it's a lot less than 2.4x). Please help me to understand.
 
RustyShackleford said:
Newbie here, wife is about to by a used 2018 Leaf. I'm a little confused about the Level2 charging. Nissan says that using an L2-EVSE charging cable, it will charge the 40kwh version in 8 hours, which is a net of 5000 watts. But they also say you need to install a 50amp/240v outlet. That's 12000watts. I understand that outlets (over-current protection devices, specifically) need to be oversized, and that there's some inefficiency in the charging circuit. Still 12000watts versus 5000watts seems a bit extreme. Against code even, as breakers aren't supposed to be drastically larger than the expected load (I forget what the factor is, but it's a lot less than 2.4x). Please help me to understand.

OK, There are a lot on nuances in this equation. The EVSE (that's the cord you plug into the wall and the car) has a 14-50 plug on it, which nominally means a 50a circuit. The EVSE itself is able to supply 32a of current. Finally the car has a maximum draw of 27.5a. 240v * 27.5a = 6.6kW then knock a few percent off for charging inefficiencies (5-7%) and you're close enough to your 5000W estimate.

So why does Nissan seem to require a 50a circuit? Technically, the circuit must be 125% of the EVSE capacity. This means you could get by with a 40a circuit. Indeed, I have a setup exactly like that and it's pretty common. However, ask most electricians to put in a 14-50, and they'll do a 50a circuit unless there's a reason to do it differently...and I recommend that you do so unless there's a technical or economic reason to put in the smaller 40a circuit.
 
davewill said:
However, ask most electricians to put in a 14-50, and they'll do a 50a circuit unless there's a reason to do it differently...and I recommend that you do so unless there's a technical or economic reason to put in the smaller 40a circuit.
Oh, it's the plug (it's a 3XB3, by the way), I see. No, no real reason not to do 50amp. I'll DIY anyhow, not that it'd matter much on cost either way. I just thought 50amp sounded grossly oversized; and I'd rather work w/ 8awg than 6awg. Thanks !
 
50 amp is fine with lighter loads. Short circuit will trip the breaker before #12 wire melts.

Only reason to get a smaller evse would be to utilize an unused dryer outlet rated 30 amps. For this you need 24 amp evse.
 
smkettner said:
50 amp is fine with lighter loads. Short circuit will trip the breaker before #12 wire melts.
Wait, what, use 12awg w/ . a 50amp breaker ?


Only reason to get a smaller evse would be to utilize an unused dryer outlet rated 30 amps. For this you need 24 amp evse.
That might actually be helpful for visiting certain friends and family. So you're saying that if I look around, I can find a charging cable that'll work with this car and only need a 30amp outlet ?

Sounds like the 3XB3 will probably work with a 40amp outlet (and maybe a 30amp), but still, if has a 50amp plug and so needs a 50amp receptable, it's a code violation to install that outlet with less than 50amp breaker and compatible wire.
 
RustyShackleford said:
smkettner said:
50 amp is fine with lighter loads. Short circuit will trip the breaker before #12 wire melts.
Wait, what, use 12awg w/ . a 50amp breaker ?


Only reason to get a smaller evse would be to utilize an unused dryer outlet rated 30 amps. For this you need 24 amp evse.
That might actually be helpful for visiting certain friends and family. So you're saying that if I look around, I can find a charging cable that'll work with this car and only need a 30amp outlet ?

Sounds like the 3XB3 will probably work with a 40amp outlet (and maybe a 30amp), but still, if has a 50amp plug and so needs a 50amp receptable, it's a code violation to install that outlet with less than 50amp breaker and compatible wire.

By code you will need at least 40 amps to power the 2018-2019 Nissan 120/240v. EVSE. A 40 amp circuit can only legally power 32 amps continuous and a 30 amp circuit can only legally power 24 amps continuous.

1- There is no such thing as a 40 amp only receptacle. For 40 amp 240v the receptacle used is a 14-50R the same for 50 amp 240v.

2- if you use THHN/THWN etc individual stranded wires in a raceway (conduit) you can run 8 AWG for 50 amps if the run is less than 100 ft. If you use NM-B romex you must use 6/3 with 50 amp 240v. NEC310.15(B)(16)

3- for the 120/240v OEM Nissan EVSE you can connect it to a 14-50R wired with 8AWG or 6AWG THHN in conduit or even non metallic flex conduit and use either a 40 amp or 50 amp double pole breaker.

I wired my barn outlet for my Nissan EVSE with 6AWG since I had some around and wired it to a 14-50R protected it with only a 40 amp breaker. It comes off a 60 amp sub panel and the receptacle is dedicated to the Nissan EVSE. The Nissan 120/240v EVSE draws 30 amps max.

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Jerryr said:
By code you will need at least 40 amps to power the 2018-2019 Nissan 120/240v. EVSE.
So there's no such thing as a charging cable that would only pull 24 amps (and so be ok w/ 30amp circuit) ?
There is no such thing as a 40 amp only receptacle. For 40 amp 240v the receptacle used is a 14-50R the same for 50 amp 240v.
Oh I see, so the '50' (in 14-50R) means it can handle 50amps but not that it's illegal to hook it to a small circuit (or at least to a 40amp).
 
RustyShackleford said:
So there's no such thing as a charging cable that would only pull 24 amps (and so be ok w/ 30amp circuit) ?

They do exist, but are not very common. More common are adjustable EVSEs that can be set to 32 A or to lower current settings. These are available for fixed installation and as portable units. If you are looking to minimize costs, you could consider a 16 A EVSE, which can be found for about $200.
 
RustyShackleford said:
Jerryr said:
By code you will need at least 40 amps to power the 2018-2019 Nissan 120/240v. EVSE.
So there's no such thing as a charging cable that would only pull 24 amps (and so be ok w/ 30amp circuit) ?

Clipper Creek makes a 30 amp 240v connectable EVSE Model LCS-30 that connects to a 30 amp Supply and pulls max 24 amps. It will provide a decent rate L2 charge at about 5.8 kw.

There is no such thing as a 40 amp only receptacle. For 40 amp 240v the receptacle used is a 14-50R the same for 50 amp 240v.
Oh I see, so the '50' (in 14-50R) means it can handle 50amps but not that it's illegal to hook it to a small circuit (or at least to a 40amp).

Yes. Most electric ranges require 40 amp 240v supply and come with a cord with a 14-50P plug that plugs into a 14-50R receptacle protected by a 40 amp breaker. Here’s an example of a 40 amp rated range power cord with that plugs into a 14-50R receptacle. https://www.homedepot.com/p/EZ-FLO-6-ft-8-4-4-Wire-Range-Cord-61273/301074807
 
Jerryr said:
RustyShackleford said:
So there's no such thing as a charging cable that would only pull 24 amps (and so be ok w/ 30amp circuit) ?

Clipper Creek makes a 30 amp 240v connectable EVSE Model LCS-30 that connects to a 30 amp Supply and pulls max 24 amps. It will provide a decent rate L2 charge at about 5.8 kw.
Thanks for these pointers (you and @mkettner). They are several hundred dollars. The only reason to try to go to a smaller amperage cable would be to be able to use with a 30amp receptacle at her son's house, the idea being it's easier to find one of those. But I think she's better off sticking with the 3XB3 that'll come with the car (i.e. free), and put that money into another 40amp outlet at her son's house if need be (he or I can install it).

I am curious though: if I bought that 30amp cord, how does the car know to pull less juice ? I'm thinking the other conductors in the connector allow the car to handshake with some kind of logic in the box in the cord, and tell it "you're actually connected to a car and not some kid's fingers" while the cord tells the car "you can only draw 24 amps from this charger (dunno why it insists on making this a hyperlink)"; do I have that about right ?

Yes. Most electric ranges require 40 amp 240v supply and come with a cord with a 14-50P plug that plugs into a 14-50R receptacle protected by a 40 amp breaker.
Duh, I actually installed one of those when we remodeled kitchen 3 years ago (with 40amp breaker and 8/3 NM-B).
 
RustyShackleford said:
how does the car know to pull less juice ? I'm thinking the other conductors in the connector allow the car to handshake with some kind of logic in the box in the cord, and tell it "you're actually connected to a car and not some kid's fingers" while the cord tells the car "you can only draw 24 amps from this charger"; do I have that about right

Yeah, that's about right, except technically, the charger is in the car and the EVSE is the 'box in the cord' plus the associated other parts (cord, plug, etc). You can find all the details if you're interested in the J1772 spec which should be freely available on the web.
 
Now we have to decide whether to spring for a hard-wired charging station, or just install a 14-50R outlet on the side of the house near where wife parks (in some sort of weather-proof housing I guess) and use the 3XB3 cord that's with the car. I guess it's cost of the hard-wired unit versus the inconvenience of she either has to leave the cord plugged in and thus not have it while she's on the road, or have to pull it out and plug it in every time she comes home.

Have to decide REAL soon too, she'll get the car Thursday ...

Oddly (especially considering our earlier discussion) it looks like the hard-wired unit that Nissan points you to:

https://www.amazon.com/dp/B07FWSGK1C/ref=s9_acss_bw_cg_vasevn_12c1_w?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=merchandised-search-2&pf_rd_r=0KKYKSKMR3QM1ZSVDCEA&pf_rd_t=101&pf_rd_p=fd2e30a2-0a4e-479c-94ae-ccda5eff82d5&pf_rd_i=19006194011&th=1

... is only 32 amps, so wondering if it'll charge the car as fast as the 3XB3 in a 40- or 50-amp outlet ?
 
RustyShackleford said:
Now we have to decide whether to spring for a hard-wired charging station, or just install a 14-50R outlet on the side of the house near where wife parks (in some sort of weather-proof housing I guess) and use the 3XB3 cord that's with the car. I guess it's cost of the hard-wired unit versus the inconvenience of she either has to leave the cord plugged in and thus not have it while she's on the road, or have to pull it out and plug it in every time she comes home.

Have to decide REAL soon too, she'll get the car Thursday ...

Oddly (especially considering our earlier discussion) it looks like the hard-wired unit that Nissan points you to:

https://www.amazon.com/dp/B07FWSGK1C/ref=s9_acss_bw_cg_vasevn_12c1_w?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=merchandised-search-2&pf_rd_r=0KKYKSKMR3QM1ZSVDCEA&pf_rd_t=101&pf_rd_p=fd2e30a2-0a4e-479c-94ae-ccda5eff82d5&pf_rd_i=19006194011&th=1

... is only 32 amps, so wondering if it'll charge the car as fast as the 3XB3 in a 40- or 50-amp outlet ?
There's normally little purpose to carrying the cord around on a daily basis. I can count the number of times I've used a portable EVSE during my 8 years of EV ownership on my fingers, and not once was it unforeseen. It's sufficient to leave it plugged in at home, and take it with you only when you are leaving on a long trip or have some other reason to think you might need it.

The JuiceBox you linked to will certainly charge the car at it's full rate. With it being the same price, you might as well buy the 40a unit...it won't charge the LEAF any faster, but if you get some other car later than can charge at 40a, you'll be ready. :)
 
RustyShackleford said:
I am curious though: if I bought that 30amp cord, how does the car know to pull less juice ?
All evse send a pilot signal (tone) to the vehicle in order to communicate the maximum amps. Range is about 6 to 80 amps.
 
The EVSE signals the current available via the pilot. If there is an amount equal or greater than the car needs the car;s charger sets the current. Any excess is ignored.

My EVSE is a 40A unit connected to a 50A circuit that charged my "B" at 49A. The same EVSE charges my IoniQ at 28.5A. The car takes what it needs and it ignores the excess..
 
Thanks for all the replies. Wife has deemed that she'll never leave the charging cable at home; we live in a relatively rural area, not super EV friendly. And it's a pain, and possibly dangerous if I don't use a GFCI breaker (which I really don't want to do*) for her to be pulling the cord out of the car and plugging in both ends, every time she comes home. Plus she'll be spending lots of time at new grandkid's house and that's 50+ miles away.

So I'll be putting in a hard-wired unit. Clipper Creek seems to be mentioned a lot here, should I consider others ? The HCS-50 or HCS-40, able to supply 40 and 32 amps, respectively ? I understand the HCS-40 can supply all the juice the Leaf can take, but maybe something else down the road ?

Do I understand correctly that the Leaf (specifically a 2018 SV) allows you to schedule a charge ? If not, I want to find a charging station that handles that, because we have super-off-peak in the middle of the night, plus it's been recommended (in another thread) to avoid charging the battery when it's hot.

* Load center is pretty full, and I don't think there are "space saver" versions of GFCI outlets.
 
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