Just finishing my workshop and am doing my finish work. On 220
electrical outlets I notice there are a couple of different styles.
What is the difference. There is on that is similar to a 110 sytle but
with one of the blades turned 90 degrees. there is also one they call
a NEMA 6(?)? All three blades are in a cricular pattern. My new
jointer recommends the NEMA but would like to know what the difference
is and why one is better than the other.
Not so much that one is "better" than the other, but that the
differently configured receptacles are rated for different maximum
current. BTW, they are all "NEMA" configurations. NEMA 5-XX are 120v
plug/receptacle configurations and NEMA 6-XX are for 240v circuits.
Here is a link to a chart of the NEMA configurations for the straight
blade (non-locking) configurations:
and for the circular blade (locking) configurations:
On Mon, 29 Oct 2007 19:14:58 -0500, Tom Veatch wrote:
"Rated" may be an unfortunate choice of words (especially when using
"for maximum current"). "Keyed" is more accurate. For example, (and I
can't speak to the locking series) the 6-15 and 6-20 are keyed
differently, and the 6-15 is for 15 A and the 6-20 is for 20 A.
However, an exception exists in the NEC which permits that in 15 and
20 A circuits (on both 120V and 240V supplies), either receptacle may
be used on a 20A line. You can't, however, use a -20 on a 15 A line.
So, clearly, the 15 A receptacle is "rated" (in tems of its ability to
carry the current) for 20 A, it's just "keyed" for 15 A plugs (a 20 A
plug won't fit into it). However a 20 A receptacle will accept both a
15 A and a 20 A plug.
All of the foregoing is thrown out the window if the only receptacle
on the circuit is a simplex receptacle--then the receptacle must match
the current capacity dictated by the wire/breaker.
Well, since - if there's only one receptacle on the circuit - the
"keying" of the device must match the current capacity (IOW, maximum
amperage) of the circuit, I'd tend to call that the "rated" capacity
of the receptacle.
But, have it your way, it's not worth arguing over..
On Tue, 30 Oct 2007 10:10:21 -0500, Tom Veatch wrote:
Well, it's not "tomato, tomahto". "Rated" implies capacity or ability
to withstand. To say a fixture is "rated for 15 A" makes it sound like
it will burn up when used on a 20A circuit. That simply isn't true.
So, it is worth arguing over...unless you're wrong.
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.
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? Do you think it might
be because the X-15 receptacles aren't intended to carry a continuous
current greater than 15 amps? That sounds like a "rating" to me.
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
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
On Wed, 31 Oct 2007 18:12:53 -0500, Tom Veatch wrote:
But it's supposed to be protected if it's mounted in a box. That's the
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.
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.
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
Well, it might very well be, if it were any other current device than
15/20 A devices.
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.
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
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.
as the ONLY outlet on a 20 amp circuit since it is "rated (that is
designed and permitted to carry said current) for 20 A service." Yet
that is prohibited by code. Wonder why?
And do you understand the reason behind allowing multiple instances of
15 amp outlets, but prohibiting a single 15 amp outlet, on a 20 amp
The difference(s) I see is simply one of semantics and is completely
limited to the single instance of allowing a 20 amp circuit to feed
multiple instances (but not a single instance) of 15 amp outlets.
However, I will admit to some interest in why you seem to feel that
the use of the word "rated" in my response to the OP was
"unfortunate". Do you seriously believe it could lead the OP into some
sort of unsafe practice?
Wow.. I would have loved the chance to pick your brain a few months ago... great
Mexican builders don't have a lot of RV experience, so when I specified a "50
amp hookup" they put in some weird kind of plug that a friend said might be from
a dryer or something...
Oh.. before we found out that it wasn't an RV outlet, we went to the States and
bought a "dog bone" to plug into it to convert it to a 30 amp plug for our
We didn't realize we had a problem until the dog bone wouldn't plug into the
Last month we took a trip to Yuma and took along the dog bone.. went top an RV
place and paid almost $50 for the outlet that fits the plug on the dog bone..
Lots more expensive and time consuming than asking a knowledgeable person a few
Please remove splinters before emailing
The NEMA ones are great! We have put them in place of the old ones we had
as the round ones are twist lock, no worry about someone accidently pulling
out the plug. Besides all my outlets are in the ceiling and not on the
floor or walls. See here for explanation:
I am getting to the point of deciding what type of heat to install in a new
workshop. The shop is 30'x54' with 10' walls and will be insulated to R-20
in the walls and R-38 in the ceiling. I have natural gas available and am
trying to decide between using one or two of the ventless "blue flame" gas
units or a single ceiling mounted vented gas furnace. The ventless units
would be less expensive and have a few other advantages, but I have heard
that because they do not vent combustion air outside of the building they
can lead to potential moisture problems. Is this an issues to be concerned
about? The shop will be used for woodworking and fossil/mineral preparation
so a moisture problem would not be good.
Thanks for any recommendations or advice any one has.
Simply put, YOU DO NOT WANT VENT LESS!!
Dumping the exhaust into the building is definitely a problem, with both
possible oxygen depletion and moisture. In my area you can not even install
vent less heaters, they are against building code. Many of them recommend
leaving a door or window slightly open when using them.
Buy a 50,000~60,000 BTU Reznor UDAP, or a Modine Hot Dawg. And be done with
Now someone will come along and contradict every thing I just wrote!
Gas is a 'wet" fuel. It comes out of the ground wet and has the
moisture adjusted to be a certain 'wetness" . This makes it easier to
pump and stabilizes the gas under pressure.
Using a ventless in a wood shop will increase the moisture content of
your product. This does not even address the rusty tools or the odor
or the possible monoxide when the heater or gas line messes up.
Depends on where and when you are. In a New England winter blowing
all your heat out through the range hood isn't all that comfortable or
cheap. On the other hand, in the summer after the house has heated to
an uncomfortable temperature, sucking in some nice cool night air can
be just the thing.
Reminds me of my parents' house in Holland. We/they had several natural
gas fired heaters that sucked in outside air to feed the burners and vented
the exhaust outside through a single coaxial opening totaling some 6"
(guessing). Worked fine, even in brick housing. Isn't there something
like that here in the US?
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