I read... somewhere... about this cool setup a fellow did w/his TS. He had
a 220v plug mounted on the side of the saw cabinet, and a pigtail that went
from the mag switch to the plug. When he was changing blades, etc. it was
very easy to unplug the saw. Additionally, "upstream" in the cabinet
mounted outlet, he had taken 1 leg of the 220 and mounted a small shielded
light and switch on the inside of the saw cabinet, so he could have a better
look-see when he dropped an arbor nut, etc.... The saw itself would be
unplugged but he still had 110 hot to check things out.
Okay, so far, so good... What I am wondering, is if you took things a bit
further, could you set up a 110 power outlet on the saw from the 220v
circuit? It would be real handy having a 110 outlet right on the saw in the
middle of the shop, without an additional power cord.
After thinking about this, I put on my safety hat. I've been doing that a
LOT more lately... would pulling 110 off of one side of the 220 create any
trouble, i.e., some sort of "disturbance in the force"... (Luke....luke....
I am your FATHER!!!) Also, what about the circuit breaker? A small 60 lamp
might not cause trouble. However, a larger load, or any load using this set
up would essentially be "unprotected" as a 110v overload may/may not trip
the 220 breaker? Is there a safe way to set this up? Is it smart? Does
this Morris Chair make my butt look fat?
Any help with those FAMILIAR would be most appreciated....
Sure, just wire the saw with a 4-wire (dryer style) plug and feed
circuit. This woudl give you the two hots (220v) a neutral (any hot to
neutral voltage of 110v) and a saftey ground.
Each "hot" on the circuit goes through a breaker. The job of the breaker
is to protect the _wiring_ on the downside, not the object plugged in. A
typical 3hp 220v saw runs fine on a 20 amp circuit so in effect you have
two standard 110v 20A circuits with 12 AWG wire. Only thing I can
think of is the breaker should be the kind that if one leg trips, it
also shuts off the other leg.
Typical 240v (and it is 240v btw) for table saws has two hots and a ground.
You "can" make a 120v circuit by using one hot and the ground, but it is
illegal and conceivably dangerous. Under very unlikely circumstances it can
make things such as the saw frame somewhat hot. Until recently all electric
dryers were wired that way (mine still is) and I never heard of anyone
getting hurt, but it is now illegal for new wiring.
To do what you want, you must have 4 wires; the 3 above plus a neutral. If
you are running a new circuit, it is very little extra expense or work. If
you are dealing with an existing circuit, you are probably out of luck; but
a simple look at the cable will tell you if it is 12/2 or 12/3 (or whatever
gauge it is.) Contrary to what someone else said, the 240v receptacle has
The disturbance in the force will create a little imbalance and increase the
voltage drop a tad, but it is almost certainly too small to be a
You raised an interesting point about unplugging your saw. With a magnetic
starter, the only way it can turn on is by hitting the "on"; it should be
perfectly safe. Still, I unplug mine before changing blades also; just
because I know it can't happen doesn't mean I am not afraid of it. I wonder
if there have been any accidents due to saws starting despite magnetic
I would be interested as well in any verified reports, as I do not unplug my
mag switched Jet TS. I figure a bolt of lightning could turn it on, but I'd
be toast before the saw ripped my hand off.
Actually no, a bolt of lightning would burn it out before it could close;
probably welding it open.
I suppose a malfunction is always possible, but odds of a malfunction for
the 10 minutes a week you have your hands in the saw, rather than in the
10,000 you don't are unlikely.
Google the thread titled "Auto-starting Unisaw"
Then see if you still think the major concern is bumping the switch
The bottom line is, an unplugged tool *can't* start, no matter *what* happens.
Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter
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You must use your REAL email address to get a response.
I have a followup question.
Let's say you wire a 120v outlet onto the circuit, then plug in, say,
a circular saw or other device with a high current draw? Obviously,
nothing as long as both the TS and the blurfl (thanks, Sylvan) aren't
running at the same time. But what if they are? Then you have lots
of amps on one hot leg, and not so many on the other, right? Will
that damage either the TS or the blurfl or the wiring or affect global
warming or something?
I have no practical need for this knowledge (and no intention of
attempting this) at this point. I was just wondering.
Compared to the blurfl, the circular saw doesn't draw that many amps. The
breaker on the 220 circuit is desiged to protect the wire, so as long as the
breaker doesn't blow, then the wire it ok. The load on the two taps in the
panel will be mismatched, but then it's always slightly mismatched depending
on what circuits are in use at any given time.
Regarding global warming, yes this will have a negitive effect due to the
conversion of the eletrical energy into some waste heat. This will cause a
localized increase in temperature, but then the refigerator that keeps the
beer cold has a much worse effect. Additional tonage in your air conditioner
can easliy correct this problem and transfer it outside and make it your
Please note, this is the opinion of a right wing conservative with only
practical knowledge of electrical issues and global warming.
Caution: The author is not responsible for any mistakes made in this
posting, because he is only human (he tries his best, nevertheless). He is
also not responsible for the consequences of any application or
misapplication of the information herein to your woodworking, other hobbies,
personal lies or environmental issue. Always appropriate safety equipment,
engage brain before engaging hands, and never, ever, ever do something only
because someone else told you to (The old jump-off-the-bridge adage our
mothers all taught us). If a process or technique does not sit comfortably
with you, then by golly, don't do it. It's better to be slow than injured.
Two issues; overloading the wiring and voltage drop.
Overloading is not important as long as you don't do it. If the TS draws
10a and the circular saw draws 5a on one leg (with the TS drawing 10a on the
other leg) then all is will as nothing is over loaded. If you plugged your
15a router in you might trip the breaker, but that is all. The fact that
the two legs are unbalanced is irrelevant.
240v is often done with somewhat smaller wire than 120v (for the same
amperage of course) because there is no return path on the 240v; so the
voltage drop is only half as much. If you start using a 240v circuit for
120v it might be undersized with a really heavy load. This would only be a
problem under certain circumstances, but is possible.
For instance, a 100' run of 240v/22a might need #10, while the same run used
for 120v/22a might require #8. (I pulled these numbers out of thin air, so
don't get on me if they are not precise) It seems odd that half the power
needs larger wire, but that is the beauty of 240v.
Whoa. Wire size is based on current, length, and allowable voltage drop.
The only reason that a smaller conductor might be allowable on 220 is that
the same voltage drop is percentagewise only half as great with 220 as it
is with 110, but that would be pretty sloppy engineering in my book.
And any electric current has a return path--in general current only flows
when there is a circuit. You may be confused because 220 has two
"hots"--one is outbound, the other is return, with the two alternating
roles 60 times (in the US) a second.
Reply to jclarke at ae tee tee global dot net
Lets say your acceptable voltage drop is 5%; your load is 20a, and your
length is 100ft.
If you are using 240v, you can use 12 gauge copper. (3.3%)
If you are using 120v, you need 10 guage copper. (4.2%)
That is exact; not the least bit sloppy or confused.
And... the 240v carries twice the power(at the same current) over the
All the advice is good, but I'd do it if I wanted to. To be dangerous, you
need leakage in the 120V device so that the case you touch gets hot AND a
defective neutral wire. If the neutral is good, the leakage will be shunted
to ground through it and will trip the breaker when the current gets high
You can't develop enough voltage across 50 feet of neutral wire to even
feel, much less hurt yourself. The code has run away from us a bit on this,
I think, but the 4 wire hookup IS better. If you get gung ho on this, you
could put a small subpanel on the saw and have some smaller breakers for the
On Fri, 16 Jul 2004 17:00:28 +0000, John Moorhead wrote:
As long as you run 4 wires (2-hot, 1 neutral, 1 ground) of the appropriate
size, it shouldn't be a problem. Just wire your 120V outlet to 1 hot, 1
neutral and ground. The 240V ganged breaker should trip if overloaded on
If it's just for the light, you could use a 240V bulb or wire up a fixture
with two 120V lamps in series across your 240V and not worry about having
to add a neutral leg.
"If you have an apple and I have an apple and we exchange apples
then you and I will still each have one apple.
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