SageBrush
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Re: A tale of two chargers

Thu Apr 15, 2021 3:05 pm

LeftieBiker wrote:
Thu Apr 15, 2021 2:40 pm
50 amp breaker for a 40 amp circuit - at least not AFAIK.
Did you write that backwards ?
2013 LEAF 'S' Model with QC & rear-view camera
Bought Jan 2017 from N. California
Two years in Colorado, now in NM
03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
-----
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LeftieBiker
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Re: A tale of two chargers

Thu Apr 15, 2021 4:51 pm

SageBrush wrote:
Thu Apr 15, 2021 3:05 pm
LeftieBiker wrote:
Thu Apr 15, 2021 2:40 pm
50 amp breaker for a 40 amp circuit - at least not AFAIK.
Did you write that backwards ?
No, but I'm having second thoughts about it. You can use a 30 amp breaker for a 25 amp device, as long as the wiring will take 30 amps. I was assuming/remembering that wiring that could handle 40 amps could also take 50, but now I'm not sure I'm correct about that. It is always best to have everything match.
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jjeff
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Re: A tale of two chargers

Fri Apr 16, 2021 4:20 am

SageBrush wrote:
Thu Apr 15, 2021 11:00 am
jjeff wrote:
Thu Apr 15, 2021 5:39 am
SageBrush wrote:
Wed Apr 14, 2021 3:26 pm
If I am not mistaken, a 14-50r is limited to 40 Amps continuous.
Actually from what I've read the outlet itself is rated for a full 50a continuous, it's just that most 50a breakers are only 80% duty rated, or 40a. I know the 14-50 outlet can be fed by either a 40 or 50a breaker as we don't really have 40a outlets, I'm not sure but doubt you could feed a 14-50 outlet with a 60a breaker which would be 48a continuous rated and ideal for a Tesla.....our resident electrician whitney is sure to know.....
Also not sure if you could purchase a 50a continuous rated breaker, or how easy it would be to find but that would also work well with a 48a Tesla charger.
It will be interesting to hear what Witney says.

I'm under the impression that the NEC wants the breaker and the receptacle to have the same Amp rating. It goes against my grain of common sense to have some components of the same rating have higher ampacity limits than others.
Offhand I can think of a couple of exceptions to that rule. #1 is a 40a breaker feeding a 14-50(50a) outlet. Apparently, this is OK as there isn't a 40a outlet in the NEMA standard, I do this but have a label on my outlet stating it's fed by a 40a breaker. The other exception I'm aware of but is kind of a different scenario is having 15a standard 120v outlets on a 20a circuit/breaker which I believe is permissible if you have more than one? outlet off that 20a circuit. I'm sure the wiring would have to be capable of 20a(12g) but I'm guessing the thought is you could say draw 10a off one outlet and 6a off another, the total circuit amps could be higher than the total draw of any one particular outlet.
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denwood
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Re: A tale of two chargers

Fri Apr 16, 2021 6:48 am

You should never have a breaker rated higher than any of the receptacles on that circuit..it can create a fire hazard. It's against code pretty much everywhere. If you have a breaker lower than the rated current on a receptacle, that is not a fire hazard issue...but may drive you a bit crazy :-)

johnlocke
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Re: A tale of two chargers

Fri Apr 16, 2021 11:44 am

All UL approved 110v outlets are rated for 20 amps even if they are 15a outlets. This is because it's common to have multiple outlets on a single 20 amp breaker. That way even if a single outlet exceeds 15 amps and the breaker doesn't trip, you're still safe. Lots of people use extension cords to plug in multiple devices which could exceed 15a in total.
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SageBrush
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Re: A tale of two chargers

Fri Apr 16, 2021 2:53 pm

johnlocke wrote:
Fri Apr 16, 2021 11:44 am
All UL approved 110v outlets are rated for 20 amps even if they are 15a outlets. This is because it's common to have multiple outlets on a single 20 amp breaker. That way even if a single outlet exceeds 15 amps and the breaker doesn't trip, you're still safe. Lots of people use extension cords to plug in multiple devices which could exceed 15a in total.
I'm confused. Are you saying that all circuits with 15 Amp breakers have 20 Ampacity wire ?
2013 LEAF 'S' Model with QC & rear-view camera
Bought Jan 2017 from N. California
Two years in Colorado, now in NM
03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

jjeff
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Re: A tale of two chargers

Fri Apr 16, 2021 3:13 pm

In my area anyway a 15a outlet can be run using 14 or 12g wiring(probably larger too but no smaller than 14g) but if any of the outlets are 20a then it would have to use 12g wire(or larger) along with a 20a breaker. Again the exception is using 15a outlets(which John said are rated for 20a anyway) on a 20a breaker.
For those who don't know a 15a outlet is what we think of as the standard outlet, 2 vertical slots, one larger than the other and a round ground. A 20a 120v outlet is the same but the vertical neutral slot(larger one) also has a vertical slot, which isn't used for a standard plug but 20a devices will have that horizontal slot instead of the vertical slot. This prevents the plug being plugged into a 15a circuit for large current draw devices.
I'm guessing the majority of 15a outlets are hooked to 15a breakers with 14g wire, my older home is this way and only kitchen and garage outlets that may or may not have 20a outlets, use 12g.
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Re: A tale of two chargers

Fri Apr 16, 2021 6:34 pm

This is likely the wrong place to post this, but since I’ve been whining about it here I wanted let everyone know that I’m now a goldmember! The delay was just an email mixup because my wife and I share a PayPal account. Mea culpa!

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johnlocke
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Re: A tale of two chargers

Thu Apr 22, 2021 1:23 pm

SageBrush wrote:
Fri Apr 16, 2021 2:53 pm
johnlocke wrote:
Fri Apr 16, 2021 11:44 am
All UL approved 110v outlets are rated for 20 amps even if they are 15a outlets. This is because it's common to have multiple outlets on a single 20 amp breaker. That way even if a single outlet exceeds 15 amps and the breaker doesn't trip, you're still safe. Lots of people use extension cords to plug in multiple devices which could exceed 15a in total.
I'm confused. Are you saying that all circuits with 15 Amp breakers have 20 Ampacity wire ?
No. I'm saying that even 15A outlets are actually rated for 20A. You still need 12g wire to carry 20A legally. If you use 14g wire you are limited to a 15A breaker. 12g wire is used sometimes when several rooms are wired to one breaker. Best practice is one breaker for each room but that requires a lot more wire and the time to string it. Cheaper to use 12g wire and wire in several rooms to one breaker. Typically done for bedrooms and small bathrooms. Living room/dining room on one breaker is common as well.
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SageBrush
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Re: A tale of two chargers

Thu Apr 22, 2021 9:48 pm

johnlocke wrote:
Thu Apr 22, 2021 1:23 pm
SageBrush wrote:
Fri Apr 16, 2021 2:53 pm
johnlocke wrote:
Fri Apr 16, 2021 11:44 am
All UL approved 110v outlets are rated for 20 amps even if they are 15a outlets. This is because it's common to have multiple outlets on a single 20 amp breaker. That way even if a single outlet exceeds 15 amps and the breaker doesn't trip, you're still safe. Lots of people use extension cords to plug in multiple devices which could exceed 15a in total.
I'm confused. Are you saying that all circuits with 15 Amp breakers have 20 Ampacity wire ?
No. I'm saying that even 15A outlets are actually rated for 20A. You still need 12g wire to carry 20A legally. If you use 14g wire you are limited to a 15A breaker. 12g wire is used sometimes when several rooms are wired to one breaker. Best practice is one breaker for each room but that requires a lot more wire and the time to string it. Cheaper to use 12g wire and wire in several rooms to one breaker. Typically done for bedrooms and small bathrooms. Living room/dining room on one breaker is common as well.
Thanks for the explanation

I kinda sorta get the intent of wanting to allow multiple 15 Amp outlets on a 20 Amp wire/breaker, but I *don't* understand why these '15 Amp' receptacles are actually rated for 20 Amps. Does a 20 Amp load on the circuit place a 20 Amp load on each receptacle ?
2013 LEAF 'S' Model with QC & rear-view camera
Bought Jan 2017 from N. California
Two years in Colorado, now in NM
03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

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