110/220 convertible table saw

txmatMarch 17, 2009

I am looking at a used Craftsman 3hp table saw that is 110/220 convertible. What is the difference between running it on 110 (which is available) and 220 (which I could make available with some electrical work)?

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220 will draw less amperage (but same wattage). Thus it is a little less electrical "strain" on the wiring. In other words, you can get by with a higher gauge (lesser diameter) wire. It will not run "cheaper" since you are paying for kilowatt-hours.

Here is a link that might be useful: Ohm's law

    Bookmark   March 17, 2009 at 2:24PM
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Thanks Bobsmyuncle. If I understand this correctly then the saw will work just as well with 110 as it will with 220. That is the horespower will be the same and therefore the cutting ability will be the same. The difference will be in how many amps will be required and hence what size circuit will be required and what else I will be able to run on the same circuit. Do I have this correct?

    Bookmark   March 17, 2009 at 3:12PM
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Pooh Bear

..... then the saw will work just as well with 110 as it will with 220. That is the horespower will be the same and therefore the cutting ability will be the same.

That's the theory anyway.
Personally, I would wire it for 220v.
No rhyme or reason as to why, it just feels better.

Pooh Bear

    Bookmark   March 17, 2009 at 5:03PM
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The motor will run cooler and last longer on 240 V.

The smallest wire you can use is #14.
A 3 hp motor on #14 wire will have a slightly longer starting time since the voltage drop in the wires will be larger.

The lower starting current on 240 V reduces the drop, allowing the motor to come up to speed more quickly.

All the rules about current and voltage only apply if you can maintain the voltage at the motor terminals under all conditions.
Start up is the worst since the motor is at stall and trying to come up to speed.

Sears is very well known for exaggerating the horsepower of electric motors they sell.

I have a Unisaw with a Baldor 3 hp motor.
By Sears 'maximum developed horsepower' it would be over 60 hp.
Repeated starts on 240 V require a 40 amp breaker.

    Bookmark   March 17, 2009 at 7:20PM
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That 3hp Craftsman saw---unless it is a built in the 70's or before-----is probably a 1.5 useable hp motor.

The 120v amperage is probably 15-18A---while the 240hp amperage is probably 7-9A per leg. You do not save any electrical use/cost---but the motor does run cooler on 240v. And the power transfer is a bit smoother.

    Bookmark   March 17, 2009 at 7:44PM
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I have a similar craftsman TS. Once I had 220 available in a shop I was using, so I converted the motor. I really enjoyed the faster startup. The thermal breaker on the motor throws pretty fast when doing heavy cutting @ 120. I never got the motor to trip the thermal breaker on 220 that I can recall.
I would go for it.

    Bookmark   March 17, 2009 at 8:50PM
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I'd hard pressed to believe that it's a true 3 hp. motor. That would pull something like 30 amps at 115v.

What's the amperage rating on the motor?

    Bookmark   March 18, 2009 at 12:23AM
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Pooh Bear

I have some Baldor motors here that are true 3 horsepower motors.
At 240v they pull 16 amps, at 110v they pull 32 amps.
This is according to the plate on the sides of the motors.

The motors were surplus (but brand new) and the application they
were using those type motors for was to drive hydraulic pumps.

I have one motor mounted under a 6x48 Delta belt sander.
I have had belts break, but never bogged one down yet.

I run these motors at 220v on a 30amp breaker.

Pooh Bear

    Bookmark   March 18, 2009 at 12:56AM
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Thanks all. I am still negotiating on price for the saw. It is about 5 years old and has the motor outside the cabinet like a contractor saw. The legs have casters on the back legs so it is semi movable. I don't recall the model number nor do I know the amperage draw. My garage is currently wired for 110, but I can add 220 without too much trouble. It was the main saw in a small cabinet (make solo) shop, so it has seen a good bit of use.

I appreciate all the comments and welcome any more you may have.

    Bookmark   March 18, 2009 at 4:38AM
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I'd think a contractor style saw would have more like a 1.5 hp motor and pull something like 14-16 amps at 120v. Most of their stuff is designed for the weekend warrior and just taken home and plugged in. Few would have a 30 amp, 120v receptacle. Of course, it could have been sold as 240v with the option of running it at 120v. But, I'm not an expert on Craftsman saws so who knows what motor might actually be installed on the saw and until with get the information there is a bit of conjecture is this thread. As others have pointed out there are some advantages to running it at 240v.

I would though the advisability of used Craftsman saw. I'd think Delta or Jet would be a better choice, especially if the old one has seem some use.

Good luck!

    Bookmark   March 18, 2009 at 8:28AM
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There is an old ( not sure what year) Rockwell Delta Model 62-273 1HP 110volt table saw available as well for about the same money. It is also an exposed motor in the rear. The Craftsman has a 50 in. extension where the Delta has only about 2ft X 2ft table. Also the Delta table needs a lot more cleaning than the Craftsman. Any comments?

    Bookmark   March 18, 2009 at 11:14AM
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I think save your money for a real tablesaw. For $150 you can gat a new portable tablesaw from Rigid or Delta that will work better than these dinosaurs. The old dual rail rip fences are frustrating to adjust and set. If you want a quality used tablesaw, look for a Delta Unisaw.

    Bookmark   March 18, 2009 at 5:51PM
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