20 amp circuits

[iwire]

Ok. Scrub the 40 and insert a 100 amp receptacle

:- )

Is it permissible to put a 100 amp receptacle in a 15 amp circuit?

Thank you.

I do not know of any code rule prohibiting that.

If there was a rule prohibiting that we could not use a 100 amp receptacle for a 70 amp circuit either.

A more common application is a 40 amp breaker protecting a 50 amp rated stove receptacle.

 

[FionaZuppa]

Here ya go.

doesnt 210.24 limit the recept to rated 15A on a 15A bc if more than one recept or outlet (there's that word "outlet" again)??

210.21(B)(1) - why does it say "not less than" ? just seems wrong. putting a single 20A recept on a 15A bc ckt ?? it almost seems backwards. if i put a 15A rated recept on a 20A bc ckt, you would just have ampacity that you cant use, but if you put a 20A recept on a 15A bc ckt you could potentially overload that circuit at a point below ocpd trip and overheat the wires??

 

[wwhitney]

doesnt 210.24

210.24 is just a summary, so we can talk about 210.21 directly.

210.21(B)(1) - why does it say "not less than" ? just seems wrong. putting a single 20A recept on a 15A bc ckt ??

The breaker needs to protect the wiring and the receptacle. If you put a 15A only receptacle (a mythical one that isn't rated for 20A pass through) on a 20A breaker, then a fault in the connected load could draw 20A all day long and cause the receptacle to fail.

If you put a 20A receptacle on a 15A breaker, then the breaker will protect the receptacle.

but if you put a 20A recept on a 15A bc ckt you could potentially overload that circuit at a point below ocpd trip and overheat the wires??

Any multiple receptacle circuit could do the same thing. If the OCPD is "overloaded below trip", then the wires will see a small long term load above their ampacity. But there is enough margin of safety in the wire ampacity so that shouldn't damage the wires. At least, if the OCPD is working properly.

Cheers, Wayne

 

[FionaZuppa]

210.24 is just a summary, so we can talk about 210.21 directly.


(1) The breaker needs to protect the wiring and the receptacle. If you put a 15A only receptacle (a mythical one that isn't rated for 20A pass through) on a 20A breaker, then a fault in the connected load could draw 20A all day long and cause the receptacle to fail.

(2) If you put a 20A receptacle on a 15A breaker, then the breaker will protect the receptacle.

Cheers, Wayne

15A recept is a 20A recept w/o the horizontal blade. its a physical diff of the insert cover/face, not a ampacity diff in the components. sure UL listed is UL listed. your 1st statement is not really real-world.

if i put a 20A recept on a 15A bc ckt?? hmmm, better to protect the recept or the wiring that snakes behind walls, floors, ceilings ?? 16A load not by fault, but because someone saw a 20A single and figured it must be a 20A ckt because a 20A recpt looks different for a reason, so their 20A cord cap is a 16A load. 15A ocpd may not trip at all and the #14 NM gets overheated.

i can see where there becomes a snafu when you start talking about the stove recepts because 1) there is no special phys diff that makes a nema 6-50 a 50A, and 2) there is no 40A nema, thus for a ckt wired to handle that 40A load the 50A recept.

i totally get it, its a mosh of this & that and nec has to accomodate somehow, so there's obviously gaps here & there. but for a single recept on a 15 or 20A bc, the recept should match the ckt rating, why? because there exists a recept that is rated 15 & 20 AND the 20 has a phys diff insert face.

 

[user 100]

15A recept is a 20A recept w/o the horizontal blade. its a physical diff of the insert cover/face, not a ampacity diff in the components. sure UL listed is UL listed. your 1st statement is not really real-world.

if i put a 20A recept on a 15A bc ckt?? hmmm, better to protect the recept or the wiring that snakes behind walls, floors, ceilings ?? 16A load not by fault, but because someone saw a 20A single and figured it must be a 20A ckt because a 20A recpt looks different for a reason, so their 20A cord cap is a 16A load. 15A ocpd may not trip at all and the #14 NM gets overheated.

The #14 and the 5-15 single would operate forever safely on that extra amp or so......

Note that wwhitney said ​mythical 15a receptacle.

 

[wwhitney]

15A recept is a 20A recept w/o the horizontal blade. its a physical diff of the insert cover/face, not a ampacity diff in the components. sure UL listed is UL listed. your 1st statement is not really real-world.

Yes, of course, but you were talking about 15A and 20A, so I responded in kind, about the non-real world 15A only receptacle. If you prefer, replace 15A/20A with 20A/30A, the point is the same.

if i put a 20A recept on a 15A bc ckt?? hmmm, better to protect the recept or the wiring that snakes behind walls, floors, ceilings ??

The OCPD will protect both, no need to choose.

16A load not by fault, but because someone saw a 20A single and figured it must be a 20A ckt because a 20A recpt looks different for a reason, so their 20A cord cap is a 16A load.

A user error that will not cause any problem, if the OCPD is working. The same error is trivial to make on a multi-receptacle branch circuit. Since an individual branch circuit is designed for a single load, and the load probably won't change very often, the likelihood of this error is much less on an individual branch circuit.

15A ocpd may not trip at all and the #14 NM gets overheated.

If the trip curve of a function 15A OCPD does not properly protect #14 NM, then there are much bigger problems in the NEC than the wording of 210.21(B)(1). I trust that the #14 NM will be properly protected by a functioning 15A OCPD--including the situation of a continuous 16A load that doesn't trip the OCPD.

but for a single recept on a 15 or 20A bc, the recept should match the ckt rating, why? because there exists a recept that is rated 15 & 20 AND the 20 has a phys diff insert face.

Clearly you feel that way, so go ahead and make a proposal for 2020. I doubt it will be accepted, as there is no safety issue with 210.21(B)(1) as currently written.

Cheers, Wayne

 

[FionaZuppa]

A user error that will not cause any problem, if the OCPD is working. The same error is trivial to make on a multi-receptacle branch circuit. Since an individual branch circuit is designed for a single load, and the load probably won't change very often, the likelihood of this error is much less on an individual branch circuit.

Cheers, Wayne

if its perfectly safe then why even bother using 15A receptacles on a 15A gp-bc? my job calls for 42 duplex receptacles, i just order a big box of 20A'ers, no mistake as to what recepts goes where, just use 20A recepts for everything, its perfectly safe if the ocpd is working, right?

as you explained it, i just not following the logic, or lack of.

 

[ActionDave]

..... i you explained it, i just not following the logic, or lack of.

It's what happens when the CMPs act on proposals that move the NEC into the area of design.

 

[iwire]

if its perfectly safe then why even bother using 15A receptacles on a 15A gp-bc? my job calls for 42 duplex receptacles, i just order a big box of 20A'ers, no mistake as to what recepts goes where, just use 20A recepts for everything, its perfectly safe if the ocpd is working, right?

as you explained it, i just not following the logic, or lack of.

Read the following please

90.1 Purpose.

(A) Practical Safeguarding. The purpose of this Code is
the practical safeguarding of persons and property from
hazards arising from the use of electricity.

(B) Adequacy. This Code contains provisions that are considered
necessary for safety. Compliance therewith and
proper maintenance results in an installation that is essentially
free from hazard but not necessarily efficient, convenient,
or adequate for good service or future expansion of
electrical use.

Informational Note: Hazards often occur because of overloading
of wiring systems by methods or usage not in conformity
with this Code. This occurs because initial wiring
did not provide for increases in the use of electricity. An
initial adequate installation and reasonable provisions for
system changes provide for future increases in the use of
electricity.


(C) Intention. This Code is not intended as a design specification
or an instruction manual for untrained persons.

They tell us straight out that the rules in the NEC are minimums and may leave customers disappointed.

 

[peter d]

The stuff that people argue over. :roll::happyno:

 

[FionaZuppa]

Read the following please
They tell us straight out that the rules in the NEC are minimums and may leave customers disappointed.

i was under assumptions we were all discussing this per that nec verbiage. nec does its best to safeguard people. that the intent.

with that said, why would nec allow a single 20A recept on a 15A bc? its not allowed if it were a single outlet with 20A duplex on the yoke. given that 20A that has special phys property to distinguish from the std 15A item, and that this special looking 20A has been around for many code cycles, why hasnt the nec adopted some verbiage for this case? a single on a 15A ckt should use a 15A rated recept, a single on a 20A ckt should use a 20A rated recept. when it come to range receptacles you dont have this issue because there is no dupes of a nema 6-'ers that are the same but only vary by an additional horizontal slot to distinguish from the other.

as for 16A running all day w/o tripping ocpd and still being safe on #14 wire. in real-world maybe, but 16A on 15A ckt w/ #14NM is bad according to ampacity chart. since the 5-'ers are most common why even allow a 20A 5- on a 15A ckt ??

 

[user 100]

The stuff that people argue over. :roll::happyno:

Tell me about it.:lol:

....since the 5-'ers are most common why even allow a 20A 5- on a 15A ckt ??

Why not allow the 5-20r ? As long as that circuit is fused correctly per wire gauge there is no issue.

 

[FionaZuppa]

Why not allow the 5-20r ? As long as that circuit is fused correctly per wire gauge there is no issue.

i dunno, it was mentioned that a 20A single on 15A ckt is very safe, thus i posed your same question a post or so ago. use 5-20r for everything, even if its a 15A gp-bc, its safe, no ?

 

[wwhitney]

i dunno, it was mentioned that a 20A single on 15A ckt is very safe, thus i posed your same question a post or so ago. use 5-20r for everything, even if its a 15A gp-bc, its safe, no ?

The only justification I can come up with for 210.21(B)(3) is that users will interact with a general purpose branch circuit long after the installer is gone. While for an individual branch circuit with a single receptacle, one can expect the installer to set up the equipment and for it to remain untouched for a long time.

It would be a rare piece of equipment that would come with a 30A plug but could be safely used on a 20A circuit. [For example, some EVSEs are rated for 24A continuous and come with a 30 amp plug, but can be downgraded via internal DIP switch to be only 16A continuous.] If such equipment is installed on a single 30A receptacle on a 20A individual branch circuit, and is configured for 20A, there's no problem.

In contrast, if you have an unused 30A receptacle on a 20A general purpose branch circuit, you are inviting the user to plug in an arbitrary piece of equipment with a 30A plug, which most likely draws more than 20A. So why facilitate creating an overload in this fashion?

Cheers, Wayne

 

[user 100]

The only justification I can come up with for 210.21(B)(3) is that users will interact with a general purpose branch circuit long after the installer is gone. While for an individual branch circuit with a single receptacle, one can expect the installer to set up the equipment and for it to remain untouched for a long time.

It would be a rare piece of equipment that would come with a 30A plug but could be safely used on a 20A circuit. [For example, some EVSEs are rated for 24A continuous and come with a 30 amp plug, but can be downgraded via internal DIP switch to be only 16A continuous.] If such equipment is installed on a single 30A receptacle on a 20A individual branch circuit, and is configured for 20A, there's no problem.

In contrast, if you have an unused 30A receptacle on a 20A general purpose branch circuit, you are inviting the user to plug in an arbitrary piece of equipment with a 30A plug, which most likely draws more than 20A. So why facilitate creating an overload in this fashion?

Cheers, Wayne

:thumbsup:

 

[iwire]

i was under assumptions we were all discussing this per that nec verbiage. nec does its best to safeguard people. that the intent.

And I was under the assumption you could comprehend all the words written in the NEC not just the ones you want to see.