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SageBrush said:
LeftieBiker said:
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.
 
SageBrush said:
jjeff said:
SageBrush said:
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.
 
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 :)
 
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.
 
johnlocke said:
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 ?
 
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.
 
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!

As you were.
 
SageBrush said:
johnlocke said:
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.
 
johnlocke said:
SageBrush said:
johnlocke said:
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 ?
 
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 ?

No. They are likely rated for 20 amps because surge loads for motors starting up can hit that, and because it makes more sense to have one basic design that can handle the higher load.
 
I'd agree that the reason the receptacles are rated for 20A is that the basic design (probably as cheap as can be....) easily supports 20A and as Leftie said, why make 2 different versions when 1 version will cover any situation.

As for the loads, any single receptacle could pull 20A or even more. Or several receptacles could each pull, say, 10A or any combination of the above. The idea is that the breaker will trip and prevent more than 20A being carried by the wire since it is only rated for that amount. How the various loads add up doesn't matter as long as the total is less than 20A.
 
goldbrick said:
I'd agree that the reason the receptacles are rated for 20A is that the basic design (probably as cheap as can be....) easily supports 20A and as Leftie said, why make 2 different versions when 1 version will cover any situation.

As for the loads, any single receptacle could pull 20A or even more. Or several receptacles could each pull, say, 10A or any combination of the above. The idea is that the breaker will trip and prevent more than 20A being carried by the wire since it is only rated for that amount. How the various loads add up doesn't matter as long as the total is less than 20A.

Which is why we have one receptacle design no matter the Amp load. We just rely on the breaker.

Oh wait ... never mind.
 
SageBrush said:
goldbrick said:
I'd agree that the reason the receptacles are rated for 20A is that the basic design (probably as cheap as can be....) easily supports 20A and as Leftie said, why make 2 different versions when 1 version will cover any situation.

As for the loads, any single receptacle could pull 20A or even more. Or several receptacles could each pull, say, 10A or any combination of the above. The idea is that the breaker will trip and prevent more than 20A being carried by the wire since it is only rated for that amount. How the various loads add up doesn't matter as long as the total is less than 20A.

Which is why we have one receptacle design no matter the Amp load. We just rely on the breaker.

Oh wait ... never mind.

The 20a receptacle just guarantees the wiring going to the outlet is 12g and it has a 20a breaker, it's for devices the mfg knows it needs to be able to supply more than 12a continuously. You should never see a 20a outlet on a 15a circuit but you could see a 15a outlet on a 20a circuit.
 
jjeff said:
SageBrush said:
goldbrick said:
I'd agree that the reason the receptacles are rated for 20A is that the basic design (probably as cheap as can be....) easily supports 20A and as Leftie said, why make 2 different versions when 1 version will cover any situation.

As for the loads, any single receptacle could pull 20A or even more. Or several receptacles could each pull, say, 10A or any combination of the above. The idea is that the breaker will trip and prevent more than 20A being carried by the wire since it is only rated for that amount. How the various loads add up doesn't matter as long as the total is less than 20A.

Which is why we have one receptacle design no matter the Amp load. We just rely on the breaker.

Oh wait ... never mind.
you could see a 15a outlet on a 20a circuit.
A 15 Amp receptacle ... rated for 20 Amps. Which would be fine, until multiple such receptacles are on the same circuit.

Sorry, but this does not make sense and it is not coherent or consistent. Manufacturers have adapted by using the 20 Amp plug if their device pulls more than 12 Amps. They are smartly ignoring the too high Amp rating of the most basic 120 Volt, 15 Amp receptacle.
 
My guess is that a 20A receptacle is meant to signify that it is attached to a 20A circuit and as such will allow a 20A appliance to be plugged into it.

A 20A (or 15A) circuit with multiple 15A receptacles is the norm in US households. The circuit breaker protects the circuit if more than 15A is pulled through the circuit.

A 15A receptacle on a 20A circuit isn't an issue. A 20A receptacle on a 15A circuit is an obvious code violation.
 
Here the norm is 15A wiring and breakers for normal household outlet/lighting circuits, and 20A for "small appliance" circuits, which are not supposed to have lights on them, only outlets. That was originally to stop the larger appliances from blowing light bulbs when they start up.
 
SageBrush said:
johnlocke said:
SageBrush said:
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 ?
Let's assume that you have a 20A breaker wired to outlets with 12g wire. You have a 15A outlet with an extension cord with a 1500w space heater, a 200w reading light and a 200w laser printer plugged in to the extension cord. you can run any 2 of the 3 devices without exceeding 15A. if you run all 3 at once though, you're at 15.8A but below the 20A limit on the breaker. If your outlet is really rated at 15A, it's overloaded but the breaker doesn't protect it. That's why the outlet is really rated at 20A current even though the outlet is not supposed to carry more than 15A. If some idiot does something stupid and overloads the 15A outlet, the outlet can still safely carry the load. The extension cord is another problem altogether.
 
johnlocke said:
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 ?
Let's assume that you have a 20A breaker wired to outlets with 12g wire. You have a 15A outlet with an extension cord with a 1500w space heater, a 200w reading light and a 200w laser printer plugged in to the extension cord. you can run any 2 of the 3 devices without exceeding 15A. if you run all 3 at once though, you're at 15.8A but below the 20A limit on the breaker. If your outlet is really rated at 15A, it's overloaded but the breaker doesn't protect it. That's why the outlet is really rated at 20A current even though the outlet is not supposed to carry more than 15A. If some idiot does something stupid and overloads the 15A outlet, the outlet can still safely carry the load. The extension cord is another problem altogether.
[/quote]
Thanks -- I get it.

Overloading the circuit with multiple loads forces NEC to match receptacle and breaker ampacities.
 
OP here, with an update.

We tested our 50 amp outlet today with our modified Nissan EVSE and it ROCKS! We took a battery at 66% to 100% in under two hours and probably less (we were watching TV and being lazy as we just had our second Phizer shots yesterday and felt a little blah.)

As soon as we plugged it in, we heard two chimes instead of the usual one, and heard a soft clunk from under the hood that doesn’t happen when we use 120v “granny” mode. Level 2 engaged, captain!

$175 for the EVSE and a couple hundred for the 50 amp circuit installation by a licensed electrician. I call that a bargain.
 
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