# 120V vs 240V for shop tools

I understand basic electricity: running wires, connecting plugs, and putting your tongue on a 120V will give you more than the tingle you get from 9 volts. But I don't understand what difference 240V will make on my table saw and other shop tools.
I'm in the process of running 240V into my shop and was wondering if I should take advantage of the feature on my table saw and band saw motors that allows them to accept 240V. They run 120V now.
Can someone tell me what running these at 240V would do for me? Will they be more powerful (i.e. not bog down easily?), improve startup time, or just run up my electric bill?
Thanks, Dave.
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On 2004-10-21 07:50:54 -0500, "Dave Rathnow"

THere is one main advantage to 240 over 120, and that is delivering twice the power before tripping a circuit breaker. Basically, most household circuits will have a 20amp breaker and appropriate gauge wire to match (the thicker the wire, the higher the breaker amperage that you can safely install). Power is proportional to the voltage times the amerpage. Hence, a 1.5HP contractor saw may suck up around 15 amps at 120v running at full duty, but only 7.5 amps when running at full duty on 240v.
Now, imagine that you have a table saw and a 1HP dust collector (let's say around 10amps at 110v) running at the same time on the same circuit. Put in a piece of 2" thick oak and push it har through your saw and the lights will go out as your circuit heats up from the 25 amps on the line. (Remember to shut of the table saw before switching the breaker back on unless you have a magnetic switch!) If you converted both to run on the same 240v circuit, this would not have happened as the draw would have been only 12.5 amps.
Lars
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said:

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Keep in mind though it is not as simple as just changing the voltage. In most cases you will need new receptacles and 2 pole breakers, and probably new wiring.
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And, there will be NO DIFFERENCE in you electric bill. Dave
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Running the tools from 240V reduces the current draw by a factor of two. You electric bill won't change, since the with twice the voltage and half the current the power is the same.
Basic advantage of 240V operation is that voltage losses in the wiring are reduced because of the reduced current consumption. This can provide slightly better motor performance in the range you are talking about, and usually better starting (when current draw is greatest).
One other effect you may notice is less flickering of other lighting in the house. Heavy current draw on 120V slightly unbalances the transformer+wiring, and the light output of an incandescent light is pretty sensitive to voltage.
-- Tom

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Typically larger tools that draw a lot of amps will be straining when the going sets tough and typically this is the time that you do not want a motor to stall or slow down because of voltage drop caused by the inability of the electrical feed not being able to supply the proper amperage. Typically with 240 volt the amp draw is 1/2 that of a 120 volt tool. Voltage drop is is typically no longer a problem and the motor does not lack for power.

I do not believe that you will see any more power other that when under a load. Again since you will probably not be having a voltage drop the motor continues to run more efficiently when under a load. Start up time may very well be more abrupt, again little or no voltage drop during the amperage sucking start up period.
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If you have a long run from the breaker panel like mine which was over 50 feet, then going to 240 made a big difference.
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On Thu, 21 Oct 2004 12:50:54 GMT, "Dave Rathnow"

If you can, you do.
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