On Wed, 31 Oct 2007 18:12:53 -0500, Tom Veatch wrote:
On Wed, 31 Oct 2007 18:53:51 +0000, LRod
wrote:
...To say a fixture is "rated for 15 A" makes it sound like
it will burn up when used on a 20A circuit...
It may sound like that to you, but not to me. A 15 amp fixture
wouldn't "burn up" if it were used on a 100amp circuit. It just
wouldn't be protected by the circuit breaker.
But it's supposed to be protected if it's mounted in a box. That's the
whole point.
Yes, a 1 amp clock radio won't burn up on a 100 A circuit--I've been
arguing that for years when folks post worrying about running their
3HP saw on a 30 or 40 A circuit. Note, however, that all of that
wiring and equipment is outside of the wall and therefore none of it
is protected by the breaker.
Why can you use a NEMA X-15 on a 20 amp circuit ONLY if there are
multiple outlets? Why won't UL list products with NEMA X-15 plugs if
they draw more than 15 amps in normal operation?
Don't ask me, ask the people who wrote the NEC--they're the ones who
authored the exception(s). Note that those people are not the same
people who run Underwriter's Laboratories, and have different
parameters, goals, and sponsors.
Do you think it might be because the X-15 receptacles aren't intended
to carry a continuous current greater than 15 amps?
Of course not. If that were true, how could you be permitted to use
15A receptacles on a 20A circuit? And you are permitted to do so, by
the NEC,
That sounds like a "rating" to me.
Well, it might very well be, if it were any other current device than
15/20 A devices.
You want to use the word "keyed"? Fine, use it. I'll continue to use
the word "rated" and I suspect that most folks will know what I'm
talking about.
Under a lot of other circumstances we can afford to be less precise in
the nomenclature we choose to use. Electricity isn't one of them. It's
irresponsible to be casual about what one says just because "most
folks will know what [you're] talking about" (and you only *suspect*
that, to boot). Well, most folks don't. That's why they're asking
questions. And this whole discussion is precisely why there are only a
handful (and a small handful at that) of posters on the wreck whose
electrical advice is worth following.
Oh, BTW, is a NEMA X-50 "keyed" for 50 amps or is it "rated" for 50
amps? I don't believe you can use the same argument here as you did
for the code exception case of multiple 15 amp outlets on a 20 amp
circuit.
I don't have technical data to prove it, but since economics doesn't
support building 20 ton components for 1 ton use, it's a fair guess
that the specification for the contacts for a 50 A device is indeed
more like a rating. After all, it's only intended and permitted on 50
A circuits. Would you not agree that no 15/20 A receptacle is built
(that is, capable of handling the current) to operate on a 50 A line?
The contacts wouldn't be able to handle the current. That's what
rating is.
That's the whole point of the argument on using that word in the 15/20
A exception. Clearly a device that is keyed for 15 A components but is
permitted to be installed on 20 A circuits is rated (that is designed
and permitted to carry said current) for 20 A service.
If you don't understand the importance of the differences I've pointed
out, there isn't any purpose served by continuing to convey them. And
if you don't, then please don't give electrical advice.
--
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net
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