Derating & OCPD

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augie47 said:
Rob, To me Art 240 addresses overcurrent protection and Art 210 addresses the circuit. To me, 210.19 still requires the conductor to have an ampacity adequate for the load. ONCE you have selected that conductor, then you go to Art 240 and select the OCP device. Art 240 allows us to use that 20 amp breaker on any load (in this situation) up to 17.5 amps.
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I have a problem with the assumption that the receptacle is the load. If 240.4(B) didn't want to allow single receptacle circuits to go up to the next standard size then why does that section use the word multi-outlet as part of the requirement? If it truly was concerned about something that may happen in the future then it should prohibit all receptacles from the next standard size rule. Clearly (to me at least :D) as written it does not.
 
augie47 said:
I'm sorry but when I read that it supports my thinking. My concern is protecting the conductor. As long as the device is rated per 210.21 it's covered. My concern is that, by the receptacle being in the circuit, the breaker is the only limit to the end utilization equipment which can in this case exceed the ampacity of the conductor thus putting it in violation of 210.10.
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I understand your concern, I don't even disagree with your concern.:)

My issue is the NEC does not support your thoughts, if you call a receptacle a 'load' you are without a doubt making up rules to fit your thoughts.
 
I don't consider the receptacle the load. I am concerned that the receptacle can allow a "prohibited load".
Let me state it a different way. Forget the receptacle. Let's hardwire a piece of equipment that requires 19 amps. The conductors are rated at 17.5. Would this not be a violation of 210.19 ? I think so because the conductor ampacity is not adequate for the load.
If we stick a receptacle in the circuit simply as a means of disconnect, does that violation no longer exist ?
Until we take steps to someway limit the current placed on those conductors to 17.5 or less, we violate 210.19 any time we connect load over 17.5 amps.
By providing a 20 amp rated outlet we allow that violation, not as a "what if' but as a manner of everyday possibility by anyone.
 
augie47 said:
I don't consider the receptacle the load. I am concerned that the receptacle can allow a "prohibited load".
Let me state it a different way. Forget the receptacle. Let's hardwire a piece of equipment that requires 19 amps. The conductors are rated at 17.5. Would this not be a violation of 210.19 ? I think so because the conductor ampacity is not adequate for the load.
If we stick a receptacle in the circuit simply as a means of disconnect, does that violation no longer exist ?
Until we take steps to someway limit the current placed on those conductors to 17.5 or less, we violate 210.19 any time we connect load over 17.5 amps.
By providing a 20 amp rated outlet we allow that violation, not as a "what if' but as a manner of everyday possibility by anyone.
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Augie, I agree with the bold part, but what words in 240.4(B) would prohibit this if a receptacle were installed as you've suggested? How are a single receptacle and a hard wired load the same thing?
 
augie47 said:
I don't consider the receptacle the load. I am concerned that the receptacle can allow a "prohibited load".
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A slippery slope. :)

Let me state it a different way. Forget the receptacle. Let's hardwire a piece of equipment that requires 19 amps. The conductors are rated at 17.5. Would this not be a violation of 210.19 ?
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IMO without a doubt yes. :)

If we stick a receptacle in the circuit simply as a means of disconnect, does that violation no longer exist ?
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If the equipment is plugged in when you are inspecting it is IMO in violation of 210.19, if it is just sitting there ready to be plugged in than not a violation.

Until we take steps to someway limit the current placed on those conductors to 17.5 or less,
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There is nothing in the NEC that requires those steps to be taken.

Can a layperson put a 150 lamp in a 60 watt socket? Do we still allow 60 watt sockets?

we violate 210.19 any time we connect load over 17.5 amps.
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Yes.

By providing a 20 amp rated outlet we allow that violation,
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By having receptacles at all allows the violation of cords under rugs or through doorways.


not as a "what if' but as a manner of everyday possibility by anyone.
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I see, It is not 'what if' it is 'suppose that'. ;):)
 
Rob, question! Based on 240.4 if there were two outlets (multioutlet), it would not be allowed, correct ?
 
infinity said:
IMO yes, we concur!
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I've reached that "point", but that seesm to conflict with Bobs' concern about and outlet not being a load.
If we have concern about two outlets, why don't we about one ?

My opionion remains but I will take a break and study.
 
augie47 said:
... I am concerned that the receptacle can allow a "prohibited load". ...
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Augie -
Just exactly where does the NEC discuss a "prohibited load"? Just exactly how would you, as the AHJ agent, stop any owner from plugging in anything they want?

As far as the NEC is concerned, as soon as the job is turned over to the owner, it is their's to do with as they please. The NEC has no bearing on what might happen.

cf
 
Thats my point, thanks! As far as the owner is concerned "if it fits and doesn't trip the breaker" it's good to go. "The job was inspected wasn't it...so it must be o.k".
In real life it prpobably makes no differerence in 99.9% if not 100% of the time, but. the owner has a circuit with a 17.5 amp capacity, he does not know that or care. He knows he has one of those "funny outlets" (20 amp) that accepts his new piece of eqiuipment (19 amp load) and off we go.
 
augie47 said:
I've reached that "point", but that seesm to conflict with Bobs' concern about and outlet not being a load. If we have concern about two outlets, why don't we about one ?
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So is a duplex receptacle one outlet or two? If it is two, then we are restricted to a simplex receptacle in the scenario being discussed. And that at least could be a clue to Joe User that this receptacle is a little different that normal.

Cheers, Wayne
 
wwhitney said:
So is a duplex receptacle one outlet or two? If it is two, then we are restricted to a simplex receptacle in the scenario being discussed. And that at least could be a clue to Joe User that this receptacle is a little different that normal.

Cheers, Wayne
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Our concern here needs to be protection of the conductors that are now derated to 17.5 amps. One single receptacle or a duplex (2 outlets) both leave us in same condition. The load for receptacles is unknown. It can be from zero to 100 or more amps. The breaker size is what protects the conductors. You tell me how i can protect the conductors in this proposed circuit. A 15 amp breaker will do this. How does a 20 amp breaker protect wires that are rated for 17.5 amps. If hard wired and load is fixed we are covered but with receptacles we can not control what is plugged in. I do not believe we can apply the next size up breaker for a receptacle.
 
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