Can 20A CB to protect NEMA 5-15R outlet branch ckt?

Status
Not open for further replies.

anbm

Senior Member
Can someone remind me which NEC rule won't allow 20A CB to protect branch circuit with NEMA 5-15R outlets? Thanks
 

kwired

Electron manager
Location
NE Nebraska
210.21(B)(1) is only for a single 15 amp receptacle on a single yoke, multiple outlets on one yoke or multiple outlets on a circuit can be on a 20 amp circuit 210.21(B)(3)
 

hurk27

Senior Member
Can someone remind me which NEC rule won't allow 20A CB to protect branch circuit with NEMA 5-15R outlets? Thanks

since you put "outlets" as in plural, there is no such code, as was said 210.21(B)(1) is only for a single outlet on a single yoke, look at the definition of an outlet in article 100:
Receptacle. A receptacle is a contact device installed at the outlet for the connection of an attachment plug. A single receptacle is a single contact device with no other contact device on the same yoke. A multiple receptacle is two or more contact devices on the same yoke.

This has been misinterpreted by many inspectors, by not knowing this definition.
 
Can someone remind me which NEC rule won't allow 20A CB to protect branch circuit with NEMA 5-15R outlets? Thanks

Is it fair to assume you have 20 A wiring going to a duplex receptacle????

I think many answers given are based on that assumption so far.

If you have only 15 A wiring going to a 15A device, then the table in 310 specifies the limits.....
 

dicklaxt

Senior Member
210.21(B)(1) says, A single receptacle installed on a branch circuit shall have an amp rating of not less than that of the branch circuit.

210.21(B)(3) says,Where connected to a branch circuit supplying two or more receptacles or outlets,receptacle ratings shall conform to the values listed in Table 210.21(B)(3),,,,,,,,,,,

Question is,,,,,,,why does the fact that when you have more than one receptacle, as listed in Table 210.21(B)(3) with a receptacle rating of 15 or 20 amps,is it permissable to hang them on a 20 amp breaker but 210.21(B)(1) says a single 15 amp receptacle cannot be hung on a 20 amp breaker?

It my eyes it looks like 210.21(B)(1) and 210.21(B3) are contradictory.I'm sure there is a logical reason for this difference but I'm not seeing it.

dick
 
Question is,,,,,,,why does the fact that when you have more than one receptacle, as listed in Table 210.21(B)(3) with a receptacle rating of 15 or 20 amps,is it permissable to hang them on a 20 amp breaker but 210.21(B)(1) says a single 15 amp receptacle cannot be hung on a 20 amp breaker?


dick


I was taught this----- lets say you have 2 appliances, each is plugged into 1/2 of a DUPLEX recep, and each is drawing 9 amps..... if you have a 20 A breaker on 20 A wire the 18 A load will hold.....

If you reverse that situation, and put a 20 A OCP with 20 A wiring to a SINGLE 15 A outlet, then when that appliance goes bad and uses more than the 9 A it was supposed to use, the device, wiring, and everything going back to the OCP will not fault until after the 15 A SINGLE device melts.... then you got a mess on your hands.....

did that make any sense??
 

dicklaxt

Senior Member
I was taught this----- lets say you have 2 appliances, each is plugged into 1/2 of a DUPLEX recep, and each is drawing 9 amps..... if you have a 20 A breaker on 20 A wire the 18 A load will hold.....

I see where you are coming from, but conversely if you only had one 9amp appliance plugged into this duplex and it faulted,,,,,,,isn't that the same scenario?If it is a bolted fault the 20 will trip as well but may not with a circuit overload,,,,,,is that what you are saying?

dick
 
I do believe we are thinking along the same lines dick, yes.

Your absolutely right that if a single 9A load were on that same ck then something similar would happen. It was taught to me that the convenience of several receps on a larger circuit out weighed the total cost of running a single circuit to every device in the facility.

The simple difference between the 2 scenarios is that if you provide 20 A of power to a 15 A single outlet, you are knowingly providing more current than the device can handle.

Since you are using more than one 15 A device on a 20A circuit, it then becomes the end user's liability issue by plugging too much stuff into their circuit....

Remember the days of edison based fuses....??
when a 15A fuse blew and it would get replaced with a 30 A fuse (until Safety fuses came out anyhow).... its really the same theory, just a different twist to it.....
 

dicklaxt

Senior Member
I think there has to be more than economics at stake here but then again :grin:who knows for sure,we were not the authors nor do we know how folks voted and their reasons .

dick
 

hurk27

Senior Member
a single receptalce will only have the rating of that one receptacle, where a duplex will have the rating on each recptacle, as well as any more receptacles on that circuit, you will still have to abide by the 50% load rule, where a single receptacle can be loaded to 80% 15 amp duplex receptacles have a 20 amp feed through rating also.
 

kwired

Electron manager
Location
NE Nebraska
They are betting that on a multiple outlet branch circuit that you will not have all the capacity of the circuit used up by one outlet. If you have a single utilization equipment that uses more than 50% of the circuit capacity then you need a dedicated circuit for that particular equipment.
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
If . . . that appliance goes bad and uses more than the 9 A it was supposed to use. . .
. . . but conversely if you only had one 9amp appliance plugged into this duplex and it faulted. . .
It's not about receptacles or appliances faulting or drawing more than they are rated to draw. It's about putting more than 15 amps through a receptacle not rated to handle more than 15 amps, and not having a breaker capable of protecting the circuit.


Now perhaps Larry is right, in that a 15 amp receptacle can indeed handle 20 amps all day long. But we are required to operate equipment within their ratings. Therefore, we cannot knowingly set up a circuit that could allow a component to sustaing a continuous overload.
 

dicklaxt

Senior Member
[/QUOTE]
Question is,,,,,,,why does the fact that when you have more than one receptacle, as listed in Table 210.21(B)(3) with a receptacle rating of 15 or 20 amps,is it permissable to hang them on a 20 amp breaker but 210.21(B)(1) says a single 15 amp receptacle cannot be hung on a 20 amp breaker?

It my eyes it looks like 210.21(B)(1) and 210.21(B3) are contradictory.I'm sure there is a logical reason for this difference but I'm not seeing it.

[/QUOTE]

I hear what you are saying Charlie and I'm not questioning that logic, my question is as stated above..:-? It still seems to me that it is the same..:confused:

dick
 

dicklaxt

Senior Member
Let me state my question in a different way,,if I have a single 15 amp rated
receptacle on a dedicated 15 amp circuit and as I read it, I am in compliance and that satisfies 210.21(B)(1),,,,,,,,,,,,now if I disconnect that receptacle and reinstall it on a different circuit rated 20 amps that already has 2- 20 amp receptacles I am in compliance and satisfy 210.21(B)(3).

If all that above as written is correct then I do not understand,,,,,,,,,,,,, where I am wrong in asking why a 15 amp receptacle in the first case can not be less than the circuit rating but can be less that the circuit rating in the second case ?

dick
 

dicklaxt

Senior Member
AHAA!!!!!! It finally sunk in,the omission of one word in my reading of the Article as well as writing it was the culprit that led to confusion.


as I read and wrote it

210.21(B)(1) says, A single receptacle installed on a branch circuit shall have an amp rating of not less than that of the branch circuit.

it should have been

210.21(B)(1) says, A single receptacle installed on an individual branch circuit shall have an amp rating of not less than that of the branch circuit.

That one word changed the whole set of rules and thoughts,sorry for being such a hardhead (duh) I must have had dreams about this last night,bad night:)

dick
 
Status
Not open for further replies.
Top