On 1/25/2016 11:38 AM, email@example.com wrote:
Who said it was "20A equipment"?
I have a 100ft spool of 12/3 and another of 10/3. Both are
capable of supporting 20A loads. Both have 20A *plugs*.
Does this mean I can never use the *wire* to support a 15A
device on a 15A outlet? Should I have to remove the 20A
plug and replace it with a 15A plug when using it in such a
situation? Or, replace the 15A *outlet* (which might only
be on a 15A branch circuit) with a 20A outlet for that
No. Run a 16AWG extension cord -- better yet, daisy chain 5 or 6 of
them together -- then throw a 15A resistive load on the end and
see what happens. (hint: 15A breaker won't trip) Do the same with
an inductive/reactive load.
Connectors are sized to the expected loads because wires are not "ideal"
conductors. They have losses (which can be complex if coiled, etc.).
The XMAS lights we use can be daisy-chained -- logical as it makes
stringing them much easier; the earlier string(s) act as extension
cords for the later strings. But, the wiring is flimsy: why size
it for 15A when the current string doesn't use more than an amp or two
and its unlikely that there will be 6 or 7 strings fed, in series,
off of that one!? OTOH, you *know* Joe Average will mindlessly
keep plugging strings into each until they've reached whatever
length they need (total number of lights). So, you put a fuse *in*
each string to ensure the fuse blows before the wire "overheats".
You don't want someone to "see" a connector at the load end of
a cord that *suggests* they can connect a 20A device there
(esp if the other end of the cord is 100 ft distant). Likewise,
you don't want to limit where a (extension) cord can be used
by fixing the connectors on each end:
- one cord with 20A plug and 20A (or 15A) receptacle
- another identical cord with 15A plug and 15A receptacle
especially when the cord -- and the reel through which it is
supplied power (think: commutating brushes/rings) -- is costly.
Instead, you (I) want to be able to do double-duty with the cord
while ensuring that anyone using it is aware of the limitations
of the circuit to which it may be connected. Having a *captive*
adapter forces the person using the cord to think about what
they are plugging it into and the consequences of that choice
(adapter on vs. adapter off).
There's a *reason* manufacturers make such adapters! Trick is finding
one that is easily "made captive".
It's perfectly acceptable to use a larger gauge of conductor,
than the baseline for a given ampacity. In fact, the code
tables for ampacity vs. gauge note that for longer runs, you
must increase the gauge to avoid voltage drop due to resistive
loading of the conductor.
NEMA 5-20R are specifically designed to allow a NEMA 5-15P, so
using 5-15P on your extention cord not only conforms to the
NEC recommendations, but is a logical move as well if have
a desire to use the same cord with a NEMA 5-15R.
YOur spools of wire are not rated for what you think they are. While the
wire will carry the current, there is enough voltage drop that you should
not be using them at 20 amps.
100 feet of # 12 should be used for up to 12 amps and 100 feet of # 10
should be used up to 15 amps from a wire chart I looked at.
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