Cord overcurrent protection for listed cords and appliances is covered in 240.5-B-1 and 3. "Listed" cords and appliances are protected when listing requirements are followed.
A single 15A receptacle can not be the only receptacle on a 20A breaker. Multiple 15A receptacles are allowed.
"Continuous" loads (over 3 hours) are limited to 80%.
When there are 2 or more receptacles, the NEC also wants an 80% limit. This is not enforceable. And UL does not have that restriction. A 15A load may have a 15A plug.
A "listed device" will have a cord large enough to be adequate when the device is used according to manufacturer instructions. The cord is allowed by the NEC (240.5-B-1).
I agree that NEC allows using a NEMA 5-20 and 5-15 receptacle protected with a
20-ampere branch circuit breaker, and as long as you don't interface a Listed appliance rated at not more than 15-amperes with these receptacles, it's a non-problem.
However, the mere fact that someone provide such interfaces, and those interfaces can be used by "Listed" cord connected equipment is proof that NEC Article 110.3 (A) (8) was not done
110.3 Examination, Identification, Installation, and Use of Equipment (A) Examination. In judging equipment, considerations such as the following shall be evaluated: (8) Other factors that contribute to the practical safeguarding of persons using or likely to come in contact with the equipment.
These are the responsibilities of the engineer of record as well as the local regulatory and code inspection agency. They have totally ignored the "Testing for Public Safety**" aspect of the "Listing" effort.
They've failed miserably with respect to this NEC article. The public is not protected because the require interfaces (receptacles) for "Listed" equipment utilizing NEMA 5-15 plugs and cord sets has not been provided for "Protection" as defined by NEC. Additionally, try to find a power cord set with NEMA 5-15 plug in your McMaster Carr catalog that's rated for more than 15 amperes! If there are any, then "ALL" listed cord connected equipment would have to use it. We have NEMA 5-20 plugs for that ... and they won't interface with a NEMA 5-15 receptacle for good reason!
A NEMA 5-15 plug and cord set applied to a 20-ampere branch circuit could be exposed to approximately 78% more real power than it's Listed rating. The conductors are essentially resistors ... and in a resistive circuit, power increases as the square of current. Subsequently (20 amperes)^2 is much greater than (15-amperes)^2. As a result, the power cord will overheat and possibly burn up. It's really quite easy to conduct this experiment with an extension cord ... but have a fire extinguisher present ... because loading up a "Listed" extension cord beyond it's listing or labeling requirements will most probably result in a fire/electrical hazard ... and since it's listing efforts (Testing for Public Safety) did not include exposing the extension cord to possible overloading (up to 20-amperes).
Wrong. What is the rating of 18ga wire? ...or are you saying that there are no appliances with 18ga wire? I suppose it's illegal to plug a lamp into a NEMA 5-15 outlet on a 20A circuit? You'd probably shit if you caught me plugging a lamp into a NEMA 5-20 outlet!
Completely irrelevant. The circuit breaker is *NOT* there to protect your cord, or appliance. Good grief! LEARN SOMETHING!
Your missing the point. If branch circuit protection in a home is 20-amperes or greater, and use NEMA 5-15 and/or NEMA 5-20 receptacles, the "Listed" appliances are not protected, and because they cannot be applied in accordance with their listing and labeling requirements.
On the other hand, if branch circuit protection in a home is 15-amperes, and use NEMA 5-15 and/or NEMA 5-20 receptacles, "Listed" appliances will be considered "Protected" according to NEC because they can be applied in accordance with their listing and labeling requirements.
This argument is a lot like which came first .... the chicken (branch circuit protection) ... and the egg ("Listed" appliances). The argument boils down to "Do you protect Listed appliances" or not? If not, get use to having latent fire/shock hazards ... and overloaded extension cord fires every X-mas!
Now there's a response that clarifies absolutely NOTHING! KRW ... Review Articles 100, 200, 300, and 400 of the latest NEC for clarification of the purpose of circuit protection. I also encourage you to contact U.L. for clarification of requirements of Listed and Labelled equipment.
... and you totally ignored NEC 110.3(1) (8): "Other factors that contribute tothe practical safeguarding of persons using or likely to come in contact with the equipment".
The issue if not about the ampacity of power cords, wall receptacles, etc.. The issue is a "Listed" appliance can and is being interfaced with a branch circuit that is beyond the Listing and/or labeling requirements of the "Listed" appliance. It not "all bets are off" at the consumer level. Such thinking totally ignores the "Testing for Public Safety" of the Listing effort. The Engineers and Architect's of Record and well as the local regulatory inspection agencies are NOT doing their job. The installations cannot be NEC compliant because latent fire and shock hazards do exists ... and the consumer doesn't even get a vote!
The smallest standard size circuit breaker is 15-amperes. Do you really think a "Listing" agency, such as U.L., AGA, CSA, ETL, etc. would put their listing mark on a product that couldn't operate safely from a 15-ampere circuit?
Does it make any sense to protect a fractional horsepower bathroom exhaust fan with a 20-ampere circuit breaker? A 15-ampere circuit breaker would provide more protected ... and is most likely what the "Listed" equipment is rated for anyhow ... because of it's fractional horsepower load.
Horsepower available from a 20-ampere receptacle: 746 watts per horsepower/hr. However, a motor is not a purely resisttive device. It has inductive and capacitive characteristics. Subsequently to answer your question, I'll need to know how many vars (a measure of imaginary power) or volt-amperes (a measure of total power), or the power factor of the motor to answer your question. In addition, is the line to line voltage 120, 240, etc? Makes a difference ... but obviously you already know that!
If you can't have multiple 15 amp receptacles on a 20 amp circuit, because someone could plug one of the everyday common devices like lamps, TV, coffee pot, etc into one, why is it that they are being installed and passed by electrical inspectors all around the country every day? Sound like the electrical inspectors who understand the code disagree with your opinion.
Your contention is that the circuit breaker has to be capable of protecting the load and it's wiring? Why then is this safety issue unique to 20 amp circuits? As has been pointed out, most lights have 18 gauge wire cords and they are connected to 15 amp receptacles, 15 amp breakers. The current carrying capability of that wire is less than the breaker rating. How is that different? When it was brought up, you just ignored it.
Perhaps you can show us examples of UL listing tags that say: "This appliance may only be used on a circuit with a 15 amp breaker". "Using it on a circuit with a 20 amp breaker is not allowed and dangerous". I've bought and used a lot of appliances, lights, etc and don't ever recall seeing any such thing. If this issue was 1% of the problem you make it out to be, you would think there would be required warning labels like that all over the place. I've never seen one.
Does it make any sense to protect floor lamps that have 18 gauge cords with 15 amp breakers on the circuits they get plugged into? Yet apparently the UL and NEC are OK with that. As for protecting the small fan with a 20 amp breaker, it depends on what else is on that circuit. If it serves other loads, that warrant a 20 amp breaker, then AFAIK, it's allowed. The motor has it's own overload protection. And if it's not allowed, perhaps you can show us the install instructions for some typical bath fans that say you can't put them on a 20 amp breaker.
It appears you have a denial problem ... and either refuse to debate the issue ... or just can't. When you grow up, I'll explain it again to you ... but with crayons!
Power: there is real, total, and imaginary power. Goggle it for yourself and perhaps you'll be enlightened.
Speaking of explaining things, why haven't you explained why the same alleged safety problem related to breaker sizing with 20 amp circuits doesn't exist when we all plug floor lamps, radios, clocks, etc that draw an amp into 15 amp receptacles.
When mommy changes your diapers, little boy, perhaps she can teach you to read.
I am an EE. I know a little more about this stuff than you pretend to, little boy. The fact that you even bring this up shows that you're flailing, trying to get *SOMETHING* to hang onto. What a doof.
just like a fundie...blame everyone else for their failures. your inability to debate is demonstrated on almost all of your posts, unless in your feeble mind calling someone a PLCCF or Liberal or Lefty qualifies as debate
Hey, every 8 feet there shall be every outlet known to man, with all devices properly "plugged" for "protection". Mr. "I can't get it right" obviously cannot figure out that by design devices are protected barring misuse or catastrophic failure. No that never happens. Far be it for a breaker to fail to trip, or a fuse. No, such things never happen.
It is not like a 4 amp short could start a fire, like something like that would ever happen.
Everything must be comfy and safe, just like life. Like something like that would ever happen.
It not a matter of what a NEMA 5-15 receptacle can handle during normal operation. It's what can it handle during a non-fail-safe incident. For example, say you have to Listed devices interfaced with a NEMA 5-15 receptacle, and each listed device is rated at 6 amperes full load. Not a problem! However, what happens when one or both fail in a non-safe manner?
Circuit breakers at the plug is a good way of getting around the problem we have in the U.S. ... and the U.S. will eventually follow their lead if branch circuit protection is not done in a manner that is compatible with "Listed" equipment.
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