On Tue, 15 Mar 2005 22:58:22 -0500, "Mark Cooper"
wrote:
I just acquired a new 6" jointer...the Craftsman which is made by Orion. It
has a (true) 1 HP motor and comes pre-wired for 110, but can be easily
rewired for 220. My questions a
1. What is the advantage of wiring for 220 vs. 110? Different Websites say
different things...some say the motor will run cooler, some say it will run
"better" (not defined!), some say it makes no difference whatsoever.
Opinions?
2. The 220 drop in my basement is the type with two straight prongs (at an
angle) and one L-shaped. The L-shaped prong carries the neutral. (It's a
30-amp "dryer outlet.") The jointer's manual says I must connect the ground
wire to a true ground. My question is...if I connect the ground wire to a
neutral instead of a true ground, am I still properly grounding the tool?
Here's the way to look at it: in most dual voltage motors there are
two windings. It is possible to connect the windings either in series
or in parallel. For 120V operation, the windings are connected in
parallel; for 240V operation, the windings are connected in series.
What all of this means is related to E=IR (Ohm's Law) and the
derivative, P=IE, and the result is half the current used at 240V vs
that used at 120V--however, the power (watts) is the same. The
windings in your motor are thus always seeing 120V so no difference in
efficiency, no change in the electric bill, and no cooler running.
If you have a stiff supply (short run of adequately sized wire) it
won't make a whit of difference which voltage you run it on. If you
have a 15A run of 50 feet, you would indeed be well served by rewiring
the motor to 240V, if for no other reason than to reduce the effect of
the high current draw (and voltage drop) at startup.
Now, erase all thoughts of a "neutral" in a 240V circuit. Ain't no
such animal. There are two 120V hot leads (180° out of phase) and a
ground, and the ground is only for safety; it's not needed to make the
motor run (dryers were permitted to use the ground as a netural so
that they could use one leg of the 240V circuit for electric timers
and such, but otherwise, the 240V feed is used for the heating coils).
If the panel that feeds your "dryer outlet" is the main load center,
Bob's your uncle, as the ground and neutral are bonded in the panel
and the third wire can truly be used as a ground with no further
effort. If the panel is a sub-panel then you must make sure the third
wire is indeed connected to the ground bus.
--
LRod
Master Woodbutcher and seasoned termite
Shamelessly whoring my website since 1999
http://www.woodbutcher.net