220v TS aux 110 v outlet - Safe, smart, dangerous??? Help!

Folks -
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....
TIA,
John Moorhead
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John Moorhead wrote:

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.
-Bruce

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Good possibility your dryer or stove has this feature already. It's the # of wires which count. Do you have 3+ ground available? Safe and effective. Even legal.

the
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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 no relevance.
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 consideration.
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 starters.
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magnetic
wonder
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.
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be
my
I'd
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.
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I think the concern is more of hitting the switch while thrashing about trying to stick your arm all the way down the throat plate opening to get the nut you dropped.
Bernie

should
just
unplug
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Google the thread titled "Auto-starting Unisaw" http://www.google.com/groups?&as_usubject=auto-starting%20unisaw
Then see if you still think the major concern is bumping the switch accidentally.
The bottom line is, an unplugged tool *can't* start, no matter *what* happens.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
Get a copy of my NEW AND IMPROVED TrollFilter for NewsProxy/Nfilter by sending email to autoresponder at filterinfo-at-milmac-dot-com You must use your REAL email address to get a response.
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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.
-Phil Crow
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<<Snip>>

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 neighbor's problem.
Please note, this is the opinion of a right wing conservative with only practical knowledge of electrical issues and global warming.
Disclaimer; 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.
Bernie
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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.
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toller wrote:

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.
--
--John
Reply to jclarke at ae tee tee global dot net
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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 smaller wires.
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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 enough.
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 smaller devices.
Wilson

had
went
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the
any
(Luke....luke....
lamp
set
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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 either leg.
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.
-Doug
--
"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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Next you'll be mounting a lap top inside and checking blade run out on the fly with a laser pointer. Geek. :)
Rich

had
went
better
the
any
(Luke....luke....
lamp
set
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