# converting a unisaw 1.5hp motor from 115 volt to 220 volt



## Beginningwoodworker (May 5, 2008)

I been thinking converting my Unisaw 1.5hp motor from 115 volt to 220 volt, I am wondering how do you do that? I hear you get more hp with 220 volt current?


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## JustJoe (Oct 26, 2012)

No you don't get any extra power. The motor just draws less amps. If your motor is switchable there should be a wiring diagram on the side or on the inside of the capacitor cover. You can get a new cord and a 220V plug to match your 220V outlet from any electrical supply store for under $5.


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## patron (Apr 2, 2009)

take the cover off where the wires go into the motor
it should have a wiring diagram there
for the conversion
(the wires are numbered
and just go to different places then)
then get the right plug for the power
(you got advice on your other post for that)


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## Beginningwoodworker (May 5, 2008)

Ok thanks!


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## shawnmasterson (Jan 24, 2013)

a lot of people think it draws less amps. This is not exactly true. If a motor draws X amps on 110 (1 leg) then it draws 1/2 the amps on 220 (2 legs). What I mean by "leg" is when you look at the wire 110 has 1 hot wire 1 neutral and 1 ground , 220 has 2 hot wires and a ground, some have a neutral. A 220 motor draws its amps from each side of the panel using the same amount of amps in total it just draws it from 2 legs not 1. It is better to run 220 because the motor runs cooler, and starts easier/faster. The wiring diagram for changing it over should be on the motor some where, and the cord will work as long as you change the plug. The plug will cost some where around $5 and the cord you have on the machine now is sized for 110 so changing to 220 the cord will be oversized. If your wanting to make the cord longer it is cheaper to buy a #12 extension cord and cut the ends off and put a 220 plug on it than to buy the wire alone. the only thing not mentioned is to make sure the starter switch is rated/setup for 220.


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## JamesT (Mar 1, 2013)

There will *NO* difference in the power of the saw at 110v or 220V. Most 1-1/2HP motors are rated at about 12 amps at 110V and would be 6 amps at 220V. 110X12=1320 watts 220X6=1320 watts. The power of the motor is the same. If the 110V circuit is sized correctly you will accomplish nothing by changing to 220.


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## Beginningwoodworker (May 5, 2008)

Thats what I tought. My motor is rated at 115 volt at 19.2 amps I think. Well I was running the motor on a 100ft exentsion cord so thats why I was losing power. In the new 12×20 garage I am going to build it will be wire.


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## knotscott (Feb 27, 2009)

It's very common for 110v circuits to suffer from voltage loss during peak demand, and starve the motor for amperage. 220v is much less likely to suffer from voltage loss, so the motor tends to start faster, and recover faster from lugging….it also tends to run cooler. If your 110v circuit is at all suspect, you might find that 220v makes a noticeable difference….not more horsepower, but faster starts and faster recovery can make it seem like it had it's Wheaties. 220v can be handy to have for bigger motors, even if you don't notice a difference on your TS.


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## Beginningwoodworker (May 5, 2008)

Maybe, but I was running my saw on a 100ft extension cord.


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## CarpenterMark (Mar 31, 2013)

Try it and see


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## guitchess (Mar 31, 2008)

Here's a metaphor for you.

Imagine a 5 gal bucket. You fill it with the garden hose and it takes 1 min. Now image that you take your hose and a hose from the neighbor's house and use them both to fill the bucket. Of course, it takes half the time.

The windings of your motor are just like that bucket. They have to fill up with electricity to turn the motor. 220v allows them to fill faster, thus improving performance. In almost every situation it will help.

Also, most table saws draw enough current that using a 100ft cord is not recommended. Unless that cord is 10 gauge or bigger.


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## wormil (Nov 19, 2011)

I've been meaning to convert my saw to 220 and just haven't gotten round to it the last 15 years or so… I'll just hardwire it though.


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## TorxNut (Mar 16, 2013)

A few years ago I converted my Ridgid 3660 table saw and Sears RAS from 120 to 240 volts. I figured the motors would start faster and maybe give a little more power. It made absolutely no difference. I even recorded the sound of the machines starting up before and after - no difference.

In this case the supply circuit was 12 gauge wire on a 20A breaker for both the 120 and the 220. Because the 120V circuit was a fairly short run with 12 gauge wire, the motors were getting all the power they needed to run properly on the lower voltage.

A 100 foot extension cord, as mentioned above, is a bad idea.

Bill


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## Beginningwoodworker (May 5, 2008)

I been using a 12 guage!


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## JamesT (Mar 1, 2013)

I repeat. If the 110 circuit is sized *correctly* it will make no difference using 110 or 220. A 100 ft. cord *is not *the way to go, way to much voltage drop. Also re-check the motor, hard to believe a 1-1/2HP is rated 19.2 amps. That kind of current draw (watts more than 2300) is more like a 3HP. 
If you are indeed drawing 19.2 amps @ 110 volts on a #12, 100 ft. cord (wiring in saw may be #14) the voltage drop may be as much as 7%-8%. The voltage reading at the saw may be 100 volts or less. Before you rewire the motor, you need an electrician to look at the entire set-up. (Just my 2 cents)


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## REO (Sep 20, 2012)

people have a tendency to think of electricity like water in a hose. often people will use the analogy and oversimplify an explanation but it is misguiding. The simple hose story leaves out resistance to flow, pressure, hose diameter etc. To get right down to it, a motor is designed to use a certain amount of electricity. it can only pass a given amount of water (HP or work) At a given pressure (110 volts) if you feed it with one hose (110) it will require a bigger hose to allow enough flow to satisfy the draw. if you split it up into two supplies (220 peak to peak 110 per leg, less if you use RMS because they are 180 out of phase.) you can use a smaller diameter hose. The total volume in the bucket over a given amount of time is still the same. smaller hoses are easier to run and carry.lol
Roger


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## wormil (Nov 19, 2011)

Water hoses are for beating employees, not filling tablesaws. We should just switch over to DC.


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## oldnovice (Mar 7, 2009)

A *100 foot 12 gauge* extension cord has approximately *0.16 Ohms* per conductor *@20°C* so if the current is *10 Amps*, there will be approximately a *3.2* volt drop just due to resistance of the extension cord.

More current required for starting which will cause the conductors to get warmer and therefore increasing the resistance and increase the voltage drop during operation. Therefore if the voltage at the outlet is 117 VAC it is possible that the voltage at the end of the extension cord, when the motor is running, could be as low as 113.8 volts.


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## JamesT (Mar 1, 2013)

oldnovice,
He said the current was 19.2, not the 10 amps example you are using. Wouldn't that mean the voltage could be as low as 100 or even less at the saw? Anyway I think we're getting off course, his question was rewiring to 220 for more power. You're post does point out there are several ways to calculate voltage drop.


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## guitchess (Mar 31, 2008)

People have a tendency to hear a metaphor and think that because it has been simplified it does not apply. The same applies to my drawing, very quick and simple.

The windings on a 220v motor have two separate paths. When wired 110v, a single supply of 110v is used to fill both windings (bucket). When wired 220v, two separate 110v feeds fill their half (bucket) simultaneously.

Red = one branch of 110v windings Blue = one branch of 110v windings. Both sets of winding can be combined: In a series - increases resistance of the windings which leads to more heat and issues arising there from. In parallel - which decreases resistance which leads to more heat and issues arising there from. Of course, modern motors are designed to minimize these issues, but there is still a theoretical advantage for 220v. 









I repeat, *regardless if it is sized correctly* running 220v will make a difference. How perceivable is that difference is the only real question. There are many variables contributing to that difference. The mass that the motor has to rotate is one of the bigger factors. You won't notice as much change on a table saw that has to start rotating a 18 oz blade as you will a dust collector with a 3 lb propeller, or a high capacity air compressor, hence larger compressors don't even have a 110v option. If it was just a "hose" size issue, you could run a 6 gauge,110v 40 amp circuit to a 5 horse.


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## oldnovice (Mar 7, 2009)

*JamesT, *I used 10 Amps just to make the calculations without a calculator! Since the actual current was closer to 20 Amps, the voltage drop would be double the numbers in my previous post or a 6.4 volt drop.

And, yes I was getting off track! When some see HP they think it is like a car which generates horsepower while an electrical component, like a motor, consumes that amount of power, ie 1HP = 746 Watts and Watts is Voltage X Current so 1.5 HP is 1119 Watts and 1119/120 VAC = 9.325 Amps, or 1119/220 VAC = 5.08 Amps, in both cases assuming 100% effeciency of the motor which is theoretical!

*guitchess* is correct in the current paths when rewiring a motor even if the drawing has bad bearings … chuckle!


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## JamesT (Mar 1, 2013)

oldnovice and quitchess,
Getting to be an interesting discussion, however I think we're getting beyond helping "beginningwoodworker". Sorry about that beginningwoodworker, didn't mean to get carried away.
quitchess, I agree with oldnovice, do something about those bearings!


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## BGST (Apr 5, 2016)

I switched my motor to 115 but the set up in the garage but pulled too many amps and kept flipping the breaker. I had an electrician install the 220 wiring but when I went to switch the motor back to 220 I realized I should have asked him to do it for me. The wiring diagram shows there are 6 wires (they are numbered 1, 2, 3, 4, 5, 8). To be 220 set up the diagram shows that #1 is alone, numbers 4 & 8 connected and 2,3,5 should be connected. Why would #1 be on its own? It was being used in the 115 set up. Thank you.


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