Any benefit in running my bandsaw on 220 instead of 110?

[Phillip Gregory]

Sorry, not true. Motor doesn't know the difference. The only real difference is that it can take a smaller wire to feed the saw.

There may be practical differences though. A 1.5 or 1.75 hp motor which draws near capacity of a typical 15 or 20 amp 120 volt branch circuit will may benefit from running on 240 volts for a few reasons:

1. A 120 volt circuit will often have other things such as lights and other equipment on it that draw power. This reduces the amount of power the tool can draw and may result in excessive voltage drop or a tripped breaker. I have many not so fond memories of our window-less basement shop plunging into darkness if we plugged the tablesaw into the outlets on the circuit that also served the lights, and bogged down its 1 hp motor on a thick rip or dado cut and tripped the breaker.

2. Voltage drop is four times as large with 120 V than 240 V as V = I^2 * R and the I is twice as large on 120 volt circuits. This is most noticeable when you have a tool plugged into an extension cord from a receptacle a good ways from the breaker panel. When I was growing up, my Dad had a 1.5 hp dual-voltage oil-lubed air compressor of course wired for 120 volts that could only be plugged into certain receptacles and run, and NEVER on an extension cord. If you plugged it into a "wrong" receptacle, it would bog down and fail to start.

3. If you do need to use an extension cord, you can use a smaller, cheaper, longer cord for 240 volt tools than 120 volt tools due to the lower amp draw.

4. If you do decide to ever convert anything to 240 volts, you will likely run a 20 amp line and that lets you run 3 hp tools. That lets you use a whole 'nother world of tools in your shop as many "decent" tools are 3+ hp and will only run on 240 volts.

I learned the lessons in #1, 2, and 4 and ended up with a shop full of 240 volt only tools, with my one technically dual-voltage tool (2 hp bandsaw with a 120 V FLA of 19.9 A, so really a 240 volt only tool) being 240 volts. I have never had to deal with any of the issues he did, and I am much happier for it. I did have to run a few branch circuits, which for me is actually kind of fun. He hated it. Which is probably why all of his tools are 120 volts only and many of mine are 240 volts.

I think the real point is being missed. The more 240 volt machines you have the better balanced the rec panel is. A good balanced panel will have very small amount of amps on neutral. Mostly when a router or lights (120 ) causes the imbalance. Ohm's law is the same on single phase 120 / 240.

Eric...the 208 motors are mostly used in factories. It takes a difference step down transformer to develop the 208....480/208

208Y is probably more common in office and urban high-density residential installations than it is in factories. A factory will have essentially everything 3-phase run on 480 and run as much single-phase on 277 as possible. They will have a little transformer for office receptacles to make 120 V. The only things that would be 208 V would be some odd stuff like a break room range oven. Residential installations will be 120/208 from the transformer as the "big" loads can't handle 277 or 480, namely clothes dryers and ranges, which are nearly always 208/240 V units. Last place I worked had three transformers; 120/208Y, 277/480Y (the largest by far), and 2400/4160Y. The massive server room and fire suppression gear ran on 2400 volts, the air handlers and kitchen ran on 480, lights were all 277 volt fluorescents, and the 120/208Y transformer fed receptacles at 120 V. Hey, everything was labeled with the little orange voltage labels and I simply saw what was labeled what. Another place I worked was 277/480 and did have a bunch of few-hundred-amp 277/480Y-to-120/208Y transformers sitting around. I walked by several disconnects for those which were clearly labeled on my way to and from the parking garage every night.

My current office of employment has a 7200/12470Y to 120/208Y 100 kVa transformer sitting outside and provides us with 120/208V service. The 8 essentially residential-size HVAC units run on 3-phase 208Y, one specialized machine is a 208/240 single-phase tool, and everything else is 120 V. I know this as we had a leg drop out to our transformer last year and got to very briefly look at the breaker panels and service drop to tell them what went wrong. They mainly looked at me slack-jawed as they did not expect a healthcare paper-pusher to know anything engineering related. But after the city engineer who came after the facilities guy couldn't diagnose the problem agreed with me, they looked at me even weirder as I was right.

[Malcolm McLeod]

After reading this (ALL), I have made a decision. Everyone here is an either an engineer or a college physics professor.

I KNEW I was gonna like it here!

[Phillip Gregory]

Guilty as charged, trained as an engineer but went into something else due to better job security (much more difficult to send to send my job to India.)

[Chris Padilla]

2. Voltage drop is four times as large with 120 V than 240 V as V = I^2 * R and the I is twice as large on 120 volt circuits. This is most noticeable when you have a tool plugged into an extension cord from a receptacle a good ways from the breaker panel. When I was growing up, my Dad had a 1.5 hp dual-voltage oil-lubed air compressor of course wired for 120 volts that could only be plugged into certain receptacles and run, and NEVER on an extension cord. If you plugged it into a "wrong" receptacle, it would bog down and fail to start.

I think you meant P = I^2 * R there.... Also, the voltage drop is twice as large at 240 V over 120 V but the current is half as much comparing 240 V to 120 V. However, the power lost in the voltage drop over the wire is what is 4 times LESS with 240 V over 120 since the current goes as the square. Since we are doubling or halving (depending on your point of view), your 2 or 1/2 becomes 4 or 1/4 due to the ^2. Current drives the size of wires or conductors. This is also why the power company sends our power out at 10s of thousands of volts...the extremely high voltage allows them to use smaller wires to send out lower current yet deliver plenty of power (P = V^2 / R = iV = i^2 * R) and then they use big transformers to step the voltage down to our customary 240 V and further split it to give us 120 V. This is also known as split-phase (don't call it 2-phase although I read that some buildings in Philadelphia actually use a 2-phase system today).

[Bud Millis]

Mike,

Using 220 is a better option - it draws less amps than 110 and seems to provide more efficient power from the motor when cutting, etc. You will need to change the plug over as well and have an outlet close by. If an outlet is not close by, make a 220 volt extension cord (I made one in 12-2 and 10-2 both 12' long with actual power tool wire from Home Depot).

[Marion Smith]

It's been explained to me, that a motor on 110v throws the power out of phase, 220 will not. I've also heard running your motors on 220 won't dim your lights like when they are running on 110. But, I'm not an electrician either.

[Malcolm McLeod]

power tool wire = 'SO' cord

[Steve Southwood]

Perhaps electrics should be added to the "No Politics & Religion" clause

Yes, electrician by trade, and no I never give an electric spec or answer. Hire an local electrician to do the work or find a local to ask the question.

[David C. Roseman]

First of all my apologies to Mike Dowell for highjacking his thread.

Mike, you're guessing right it is the cheap chinese import that is the problem, whether Grizzly, Shop Fox, Craftex or G I the motors are all the same, these motors are not of the greatest quality.
I hooked on my Amp meter when the motor was still wired 120 and the amps spiked so high for a split second I couldn't even get a reading before the breaker tripped, after rewiring the motor to 240 everything is just fine (7 Amp on startup with blast gate open) and it runs smoother than it ever did on 120. Is it worth having the motor checked out and maybe rewired - no, unless it happened during the warranty period. I doubt this would happen with a Baldor, Leeson or Siemens motor. You get what you pay for .

John, we are all victims of our own experience, but this doesn't sound right. You may well have been tripping a 120v breaker with that particular motor (did you try switching out your breaker, BTW?), but it is hardly grounds for your generalized bashing of "chinese imports". In fact, the saw Mike says he has is the well-regarded Grizzly G0555. That saw and motor are made in Taiwan, not China. And in any event it is demonstrably untrue that "the motors are all the same" among the various bench machines from the vendors you list.

Anecdotally, just last week the 30-y/o "made in the USA" General Electric 1 hp motor on the smaller of my two bandsaws (a Rockwell-Delta 14") finally gave up the ghost cutting green Sycamore blanks for a turning workshop we hosted. I wanted to replace it quickly, so ordered a 1 hp Taiwanese motor from Grizzly. The new motor arrived in just two days with standard shipping, and has more torque, is quieter, and runs cooler than the G.E. motor ever did.

[Ole Anderson]

One factor that hasn't been brought up is that a band saw (and a dust collector) have in effect a heavy flywheel that must be brought up to speed. As a motor comes up to speed it draws significantly in excess of its nameplate amp rating. My 2 hp DC runs on 240 vac and while running draws generally less than 10 amps, but on startup draws nearly 70 amps. I will leave it to another to explain why. A TS has just a fairly light blade to bring up to speed, so the heavy amp draw is for milliseconds, whereas it could take a BS ten times (or more) that amount of time to come up to speed while drawing a heavy amp load. It is during that heavy amp load that that you might notice the lights dimming. The start capacitor helps supply the heavy start current. And if you are running on a fused panel, that is why you need time delay fuses on motor circuits.

[Dan Friedrichs]

The start capacitor helps supply the heavy start current.

No, that's not true. The start cap produces a phase shift on the start winding so that the motor is pulled in a particular direction. Without a start cap and winding, the forces pulling a (stopped) motor CW or CCW would be the same, and it would just sit there. The start cap is part of the system that gets the motor going in the correct direction, but it has nothing to do with reducing inrush current.


Your other point about inrush currents being larger is true, but it goes back to what everyone has been saying: if the circuit is properly sized, it doesn't matter if it's 120 or 240.

[David C. Roseman]

One factor that hasn't been brought up is that a band saw (and a dust collector) have in effect a heavy flywheel that must be brought up to speed. As a motor comes up to speed it draws significantly in excess of its nameplate amp rating. My 2 hp DC runs on 240 vac and while running draws generally less than 10 amps, but on startup draws nearly 70 amps. I will leave it to another to explain why. [snip]

Ole brings up an important point, and I wonder if it explains why some of us have definitely noticed improved performance converting induction motors on some machines from 120v to 240v even on circuits that are sized to minimum NEMA standards and have short cable runs.

[Dan Friedrichs]

Ole brings up an important point, and I wonder if it explains why some of us have definitely noticed improved performance converting induction motors on some machines from 120v to 240v even on circuits that are sized to minimum NEMA standards and have short cable runs.

Sure, but I think what usually happens is:
1) Someone decides their equipment isn't working to his satisfaction on a shared, undersized, long-run, 120V circuit
2) He decides to correct this by installing a dedicated, short-run, heavy-gauge circuit and use 240.
3) Tool works "way better". Must be because of the 240.

If that same new dedicated, short-run, heavy-gauge circuit were run on 120, you'd likely get just as good of performance, it's just that few people do that, because they've been convinced that "240 is better!"

In retrospect, I wish I hadn't bothered with 240V circuits in my garage - they limit where I can move equipment. There is a certain convenience factor of having 120V standard outlets everywhere, versus a mix of 120 and 240.

There are really only a few reasons to run 240:
1) You have a motor large enough (7.5HP+) that can't be run on 120
2) You are running new circuits, and the incremental cost of heavier-gauge wire (for 120 circuits) is significant enough that you're willing to forgo convenience for that cost savings
3) You have an existing circuit that would be undersized at 120, and you don't want to replace it, so you'll switch the motor to 240

[Chris Padilla]

Run 10/3 everywhere and you'll future-proof your shop for 99% of what you'll ever need. It'll be just a matter of changing the breaker and outlet if you're converting from 120 V to 240 V or vice versa.

Dan, I would add a 4) to your list albeit it probably is relatively insignificant. The power loss in the wall wiring and any extension cord running at half the current of a 120 V circuit IS less.

[Mike Henderson]

Sure, but I think what usually happens is:
1) Someone decides their equipment isn't working to his satisfaction on a shared, undersized, long-run, 120V circuit
2) He decides to correct this by installing a dedicated, short-run, heavy-gauge circuit and use 240.
3) Tool works "way better". Must be because of the 240.

If that same new dedicated, short-run, heavy-gauge circuit were run on 120, you'd likely get just as good of performance, it's just that few people do that, because they've been convinced that "240 is better!"

In retrospect, I wish I hadn't bothered with 240V circuits in my garage - they limit where I can move equipment. There is a certain convenience factor of having 120V standard outlets everywhere, versus a mix of 120 and 240.

There are really only a few reasons to run 240:
1) You have a motor large enough (7.5HP+) that can't be run on 120
2) You are running new circuits, and the incremental cost of heavier-gauge wire (for 120 circuits) is significant enough that you're willing to forgo convenience for that cost savings
3) You have an existing circuit that would be undersized at 120, and you don't want to replace it, so you'll switch the motor to 240

I don't disagree with your primary thesis but I would say that most of us wire our shops with 12 gauge wire, which is too small for a 7.5HP motor at 120V. I don't even know if they make 7HP motors that will run on 120V.

My recommendation - for a normally wired shop, say with 12 gauge wire - is to go 240V for anything over 1.5HP.

The big advantage of staying 120V is flexibility - it's much easier to move tools around. Once you go 240V you'll probably have to run new wire if you rearrange your shop.

Mike

[But I do agree that with a proper circuit, motor performance will be the same at 120V as at 240V. Most people who have problems running a motor on 120V have a circuit problem.]

[And to address the comments about "balanced current" on the feeder wires: It doesn't matter if there's current flow in the neutral between the grid and your main box. The neutral wire in that circuit is sized to take the full current flow - it's the same size as the two "hot" wires. I can't think of a single problem with having current flow in that wire.] [And, of course, the current flow in the neutral will be the difference between the current flow in the two hot wires. So if one hot is carrying 20 amps, and the other hot is carrying 10 amps, there will be 10 amps flowing in the neutral.]