Did you write that backwards ?LeftieBiker said:50 amp breaker for a 40 amp circuit - at least not AFAIK.
Did you write that backwards ?LeftieBiker said:50 amp breaker for a 40 amp circuit - at least not AFAIK.
SageBrush said:Did you write that backwards ?LeftieBiker said:50 amp breaker for a 40 amp circuit - at least not AFAIK.
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.SageBrush said:It will be interesting to hear what Witney says.jjeff said: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.....SageBrush said:If I am not mistaken, a 14-50r is limited to 40 Amps continuous.
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.
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.
I'm confused. Are you saying that all circuits with 15 Amp breakers have 20 Ampacity wire ?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.
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.SageBrush said:I'm confused. Are you saying that all circuits with 15 Amp breakers have 20 Ampacity wire ?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.
johnlocke said: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.SageBrush said:I'm confused. Are you saying that all circuits with 15 Amp breakers have 20 Ampacity wire ?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 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 ?
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.
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.
A 15 Amp receptacle ... rated for 20 Amps. Which would be fine, until multiple such receptacles are on the same circuit.jjeff said:you could see a 15a outlet on a 20a circuit.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.
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.SageBrush said:johnlocke said: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.SageBrush said:I'm confused. Are you saying that all circuits with 15 Amp breakers have 20 Ampacity wire ?
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 ?
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