Switching small stationary tools to 220v [Archive] - Sawmill Creek Woodworking Community

Mike Henderson

09-09-2008, 8:38 PM

As far as the motor itself, there is no difference in operating it at 110V or 220V. It will produce the same power, the same heat, it will have the same starting torque, and it will last as long.

The reason large motors are operated on higher voltages is to reduce the current into the motor (that means the circuit supplying it can be of smaller wire). But small motors take so little current at 110V that there's just no advantage to switch them.

The disadvantage of switching a small motor to 220V is the availability of 220V. If you decide to rearrange your shop, you'll incur a big cost to move your 220V supplies. If you leave them at 110V, you can just plug in to the nearest outlet.

Someone (Rick C.???) had a guideline that anything less than 2HP should be left on 110V. Anything greater than 2HP should be put on 220V, and exactly 2HP can go either way. I think that's a good rule of thumb.

Mike

Tom Veatch

09-09-2008, 8:55 PM

...I've heard that 220 is easier on the motors than 110...

In a derivative sense, it might be, but isn't a dyed-in-the-wool given. The difference between running a multivoltage motor on low or high voltage is that configured for low voltage, the coils are wired in parallel. For high voltage, they are connected in series. The effect is that you get the same voltage drop across each coil in either case. So in a real sense, the motor doesn't know whether it's being fed from a high voltage or a low voltage supply.

The advantage to running on high voltage is that the amperage draw of the motor is half the low voltage current. Since the voltage drop in the wiring to the motor is E=IR (Ohm's Law), half the amperage through the same wiring gives half the voltage drop. That means that of the power you buy from the utility company, there will be less lost to transmission losses and more available at the motor. Whether the power loss can be characterized as "slight" or "considerable" is entirely dependent on the total resistance in the conductive path (wiring) feeding the motor.

With twice the voltage and half the losses, the Percentage Voltage Drop in the high voltage case is 1/4 that of the low voltage case. The effect will be most noticable during motor startup when the motor is drawing several times its full load current. That's when both current and line losses are maximum. You may see the motor start easier and faster on the high voltage and a little more resistant of bogging down. That's due to less power being lost to resistance in the wiring.

Not everyone sees a noticable difference, while for some the difference is fairly dramatic. It all depends on the particular wiring installation. Converting to 240v will not increase the HP rating of the motor. The only time the high voltage benefit appears is under conditions of high current draw - start up and heavy/over loaded conditions. Under those circumstances the motor will be able to produce a little more power due to the reduced voltage drop and power loss in the wiring.

If you have the circuitry installed to feed your tools 240v, there is absolutely no downside to converting a stationary tool to the higher voltage. It only takes a few minute to reconnect a couple of wires in the motor's junction box. And you just might see a little "peppier" performace from the motors. Or, you may not.

For what it's worth, every tool I own that has a dual voltage motor has been converted to the 240v configuration. Certainly doesn't hurt, and just might help.

Eric Larsen

09-09-2008, 9:07 PM

Heh...

If I want to rearrange my shop, I'm going to need a forklift. The sander is staying put.

Based on the replies, I think I'm going to switch over the molder and bandsaw. I'm going to be doing a lot of resawing in the very near future, so why not.

The DC sometimes finds it's way into the house for cleaning the REALLY BIG MESSES, so it will stay 110... (I once dropped a bag of flour in the kitchen. I won a bet with SWMBO that I could have it cleaned up in 15 minutes flat.)

The disadvantage of switching a small motor to 220V is the availability of 220V. If you decide to rearrange your shop, you'll incur a big cost to move your 220V supplies. If you leave them at 110V, you can just plug in to the nearest outlet.

Jim Becker

09-09-2008, 9:09 PM

Tom, a dual voltage motor is going to work identically no matter which voltage you choose. The windings will draw exactly the same current (amperage). All you are doing when you switch the voltage is rearranging how the windings are arranged in the circuit. There is a very small set of motors "out there" that are designed to supply slightly more horsepower under 240v, but they are not common. So the net-net is switch if it is convenient for your use, but don't expect any change in performance. You are correct that there is no downside to conversion...outside of the cost for termination hardware, however. Rick C has covered this in depth a number of times at SMC.

Tom Veatch

09-09-2008, 10:16 PM

Tom, a dual voltage motor is going to work identically no matter which voltage you choose. The windings will draw exactly the same current (amperage). All you are doing when you switch the voltage is rearranging how the windings are arranged in the circuit. ...

I thought that's what I said.

Windings connected in series for high and parallel for low means the same voltage drop across each set of windings in either case. Same voltage drop + same windings = same current. So we agree that the same current will flow in each set of winding whether connected for high or low voltage.

You get twice the current with the parallel (low voltage) connection because different electrons flow through the separate (parallel connected) winding so the amperages add. With series connection, the same electrons flow through both windings and an electron only get counted once for determining amperage.

I don't see where there's any disagreement.

scott spencer

09-09-2008, 10:27 PM

If you've got 220v already, then I'd do it. But unless you're experiencing dimming lights or other issues, it's probably not worth the time, cost, and effort.

I did switch both my GI50-185 contractor saw and 22124 hybrid saw to 220v. Not much difference with the GI, but with the 22124 I definitely noted faster startup and quicker recovery time from slowups. I'm guessing due to less voltage loss during those very high peak amperage moments.

Gary Curtis

09-09-2008, 10:49 PM

220 = Bragging rights! Pure and simple. My tool is bigger and badder than your tool. Seen it many times right here on this forum.

Seriously, what Mike and Tom said provides the scientific rationale. My shop was just constructed along with a new house, so I had the opportunity to arrange all electrical hardware. I was even entertaining thoughts of getting 3-phase current. Crazy me!

I run a few 2hp motors, a 5hp motor on 220. The dust collector at l.5hp is on 110 and the same for anything smaller. By the way, the national electric specifies that (depending on the circuit size) only one 220 machine can be plugged into a given circuit at a given time. So in my shop there is a lot of 'plug in, plug out' going on constantly.

Gary Curtis

Alan Schaffter

09-09-2008, 11:34 PM

What Tom said about the machines.

One consideration if you have a small shop breaker panel- you will likely need to go to half-width c/bs for any new 220V circuits. Another small shop consideration is there are often multiple outlets on each 110V branch and so there may be multiple items on that circuit. Adding a 220V circuit and switching a few tools to 220V reduces the load from the 110V circuit. Do your lights dim when you turn on a machine? :D There is no change to the overall capacity of the panel.

Jim Becker

09-10-2008, 9:30 AM

Tom, I guess I miss-read your post and I apologize accordingly.

Lee Schierer

09-10-2008, 12:07 PM

I agree that the motor will perform the same on either voltage. In large industrial applications the higher volatages are used so that lighter gauges of wiring can be used. Lighter gauges means less copper which means less cost both for material and the labor to pull them.

Tom Veatch

09-10-2008, 2:13 PM

Tom, I guess I miss-read your post and I apologize accordingly.

No problem, Jim, and no apologies needed.

Sometimes my brain, what's left of it, and my keyboard don't work on the same frequency so what I write comes out not being what I meant. In fact, rereading my response, it comes across as maybe being a little surly. If anyone saw that in it, be assured that was not my intention.

Thanks for checking me.:)

Brian Kincaid

09-12-2008, 9:40 AM

There was a definite difference between running 110 vs 220 on my Delta contractor table saw. The start-up is faster and it doesn't bog down on 2" resaws anymore. That was my experience, but YMMV.

I have always read that heat is a motor-killer, and that a motor run off 220 has less current, therefore much less heat. Makes sense to me since P=I^2 R, but I haven't dug any deeper.

-Brian

Anthony Whitesell

09-12-2008, 10:05 AM

In general, for the smaller tools you won't notice any difference. In the 1 1/2 to 2 HP range (15-20 amps), the difference may become noticeable. I would leave anything less than 1 HP alone (<10-12 amps). I don't think it's worth the time, cost, or hassle.

P=IV. Twice the V half the I (amps) same power, same heat. High V, higher starting torque, faster spin up, but not by too much. Some people may notice, some won't.

Line losses will come into effect a little. More line losses occur as the amperage goes up making the meter spin a little faster. As a hobbiest and the time spent in the shop on a monthly basis probably wouldn't make much of a difference.

Jim Becker

09-12-2008, 4:05 PM

Carl Babel

09-12-2008, 5:08 PM

I'm going to jump on the "made a big difference in my contractor saw when I converted" bandwagon. The primary difference was in ripping thick hardwoods - the saw just didn't bog down when wired for 240V.

That being said, I agree with previous posters that there should be no difference inside the motor. As previously stated, the supply lines are the reason for the difference - I was getting dimming of lights when using my saw with 120V.

BTW, I got an even bigger boost by going to a link belt, but that's a subject for a different thread...
:D

Mike Henderson

09-12-2008, 6:21 PM

It's not half the current/amps, folks. The same amount in aggregate is drawn from the power company when you convert to 240v. It's just split between two hots instead of one on the way to the motor. When you do notice increased "pep" it's probably because the wiring in the wall is playing happier, especially at startup and when the motor is under heavy load.I'm afraid Jim has a misconception about how the power distribution works in a home.

It absolutely is half the amps at the higher voltage (220V) than at the lower voltage (110V). In both cases, the load is supplied by two wires and the current flows through both wires.

What confuses people is that, in the US residential power distribution system, one leg of the 110V distribution is tied to ground. But from a "delivery of power" that makes absolutely no difference. You could remove that ground and the system would work exactly the same, except there would be a safety concern. In certain European residential distribution systems, there is no ground. The advantage is that you can grab one of the hot leads and you won't get shocked because there's no return. The disadvantage is that you can have an inadvertent ground in the system and not know it. Then, if you grab one of the hot (not the grounded leg) wires you'll get fried.

I prefer the grounded system, but I'm sure the Europeans prefer the non-grounded system.

But back to the original issue, a motor draws the same POWER, whether you operate it on high voltage or low voltage. Since the high voltage is twice the low voltage, it must draw half the amperage to equal the same power.

Mike

Jim Becker

09-12-2008, 9:44 PM

I stand corrected, Mike. My apologies for misstating this to all...

David Freed

09-13-2008, 11:58 AM

I'm afraid Jim has a misconception about how the power distribution works in a home.

It absolutely is half the amps at the higher voltage (220V) than at the lower voltage (110V). In both cases, the load is supplied by two wires and the current flows through both wires.
..................
But back to the original issue, a motor draws the same POWER, whether you operate it on high voltage or low voltage. Since the high voltage is twice the low voltage, it must draw half the amperage to equal the same power.

Mike

I agree with your explanation. I hope you don't mind if I add something to it.

Since Volts x Amps = Watts, you could substitute the word "watts" in place of "power".

A motor draws the same POWER (number of watts), whether you operate it on high voltage or low voltage. Since the high voltage is twice the low voltage, it must draw half the amperage to equal the same power (watts).

I thought this might help some people because everyone pays for their "power" according to how many watts they use.

There was a definite difference between running 110 vs 220 on my Delta contractor table saw. The start-up is faster and it doesn't bog down on 2" resaws anymore. That was my experience, but YMMV.

I have always read that heat is a motor-killer, and that a motor run off 220 has less current, therefore much less heat. Makes sense to me since P=I^2 R, but I haven't dug any deeper.

-Brian

I'm going to jump on the "made a big difference in my contractor saw when I converted" bandwagon. The primary difference was in ripping thick hardwoods - the saw just didn't bog down when wired for 240V.

I was getting dimming of lights when using my saw with 120V.

:D

I would say that the reason both of you noticed such a difference in your saw when you changed voltage is because you were overtaxing the circuit it was on, which was causing a noticable voltage drop. This is where the line losses that Anthony mentioned comes into play. The lights dimming indicated that you were drawing more current than the wiring could handle.

If you had originally had your saw on a dedicated 110 circuit, with the proper size wiring, you probably wouldn't have noticed much difference. In your cases you did need to get your saws on a different circuit, whether it was 110 or 220 volts. Excessive voltage drop is hard on motors because it will make them run hot. Running them on 110 or 220 makes no difference in how hot they run, though, because the same amount of power (or watts) is required.

Mike Henderson

09-13-2008, 2:40 PM

I have always read that heat is a motor-killer, and that a motor run off 220 has less current, therefore much less heat. Makes sense to me since P=I^2 R, but I haven't dug any deeper.

-Brian
There is no difference in the heat. I've seen your equation used many times to "justify" using a higher voltage but you have to look a bit deeper to understand why the heat is the same - in other words, "P" is exactly the same whether you run the motor on high voltage or low voltage.

The quick answer is that the current (I) is twice as high in the low voltage operation but the resistance (R) is one fourth.

The way a motor is wired so that it can operate on dual voltages is that the field is divided into two coils (logically - it could be more than two coils but will always be an even number). For high voltage operation, those coils are put in series. For low voltage operation, those coils are put in parallel.

See the attached drawing. Let's assume each coil has a resistance of one Ohm (if you don't like using 1 Ohm, use your own value). When the coils are in parallel, the effective resistance of the two is 0.5 Ohm. When the coils are in series, the effective resistance is 2 Ohm.

Doing this mathematically, let's let R= the resistance at low voltage. Therefore, the resistance at high voltage is 4R.

Let's let I= the current at high voltage. That means the current at low voltage is 2I.

Plugging into your equation for low voltage we get.

P=4I^2*R

For high voltage we get

P=I^2*4R

The two equations are the same and the heat is the same.

[You can check this by using one of the other equations for power (or watts as David mentioned above), P=V*I. Note that when we change the voltage by a factor of two, the current changes by the inverse. So let's let low voltage = V. Therefore high voltage will be 2V.

Let current at high voltage be I. Therefore, current at low voltage will be 2I.

The equation for power at low voltage will therefore be:

P=V*2I

Power at high voltage will be:

P= 2V*I

Again, exactly the same.]

Mike

[As far as the motor itself, there is absolutely no difference between operating it at low or high voltage. The difference is in the circuit supplying the motor. If you have a proper circuit supplying it, it will operate the same. A proper circuit is one which will supply rated voltage under all conditions of normal operation. That is, when you start or load the motor, the voltage does not drop below the rated voltage on the motor.]

David Freed

09-13-2008, 4:40 PM

Plugging into your equation for low voltage we get.

P=4I^2*R

For high voltage we get

P=I^2*4R

The two equations are the same and the heat is the same.

What does this symbol mean? ^ Better still, explain that whole equation if you would. I am 99.99% sure I agree with you, but I am not sure what I am agreeing with. I am not up on electical equations. I only went to the redneck school of electricity.

Mike Henderson

09-13-2008, 5:22 PM

What does this symbol mean? ^ Better still, explain that whole equation if you would. I am 99.99% sure I agree with you, but I am not sure what I am agreeing with. I am not up on electical equations. I only went to the redneck school of electricity.
In Excel, the ^ means "to the power of". I didn't use parentheses so the equation is ambiguous, but I felt people would know what it means.

So the first equation could be read as:

power equals four times (current squared) times resistance

Note: resistance (R) is what we defined it to be - the resistance at low voltage. Current is also what we defined it to be - the current at high voltage. The current at low voltage is twice the current at high voltage, so when we compute the power at low voltage we must use 2I instead of I. When that is squared, we come out with 4*I^2.

The second could be read:

Power equals (current squared) times four times resistance. The resistance (R) is what what we defined it to be - the resistance at low voltage. Since we know that the resistance at high voltage is four times the resistance at low voltage, when we compute the power at high voltage, we must use 4*R to represent the real resistance at high voltage. The current was defined as the current at high voltage, so it is just I^2 in the equation.

In this case, I added the parentheses to clarify things. The material in parentheses should be evaluated first, then the other operators used.

I hope that's clear. If not, let me know and I'll try to add to my explanation. In algebra we can define variables to be anything we want them to be, as long as we use them consistently. The results will be exactly the same. For example, we could have defined R to be the resistance at high voltage and I to be the current at low voltage. As long as we are consistent, we'll get exactly the same results. But we normally choose variables so that it's easy to compute with them, which is what I tried to do here.

Mike

David Freed

09-13-2008, 6:35 PM

Thanks for the explanation. I understand it now, but I will still let you figure out those kind of equations. I can wire my shop and machines (including 3 phase), so that is good enough for me.

Michael O'Sullivan

09-13-2008, 6:59 PM

Tom Veatch

09-13-2008, 7:16 PM

...My first question is, why does a 220v circuit require 2 breakers? If amperage were the only issue in wire size, 1 should suffice.

Because a 240v circuit has two wires that are "hot" relative to ground. Either one of those wires could independently develop a short to ground. Therefore each wire has to be independently protected with a breaker. The breakers are ganged together with a common trip so that if either wire has excessive current for a period of time long enough to trip the breaker, both breakers trip and shut off power to the entire circuit, not just the wire that is overloaded.

Second, is the improvement people see in their performance when rewiring for 220v a result of that tool being on a dedicated and adequately wired circuit? ....

Possibly, even likely, but not necessarily.

The improvement is due to reduced voltage drop in the supply wiring. That could be because of reduced amperage draw through those wires, or it could be because of reduced resistance in a new circuit, or some combination of the two. The only way to definitively answer your question for a specifc case would be to set up a test in which the same wiring was used for both voltages and compare the difference. If you convert a tool from 120 to 240 and then run it on a different circuit, you have changed 2 things in the setup and, in general, it's impossible to state which of the two contributed most to the change in the result.

Eric Larsen

09-13-2008, 7:29 PM

Man, I am loving this thread.

I still haven't swapped the tools over, because I realized I'd need to make the cords considerably longer.

I really appreciate the insight, Tom & Mike.

David Freed

09-13-2008, 7:47 PM

I have always suspected that the reason for "lights dimming" is a circuit that is overloaded and drawing power away from the rest of the location (but not quite tripping the breaker).

Go here to see another extensive explanation about lights dimming when you turn on one of your machines. http://au.answers.yahoo.com/question/index?qid=20071231194603AAuf2wB

When I had my shop in the basement of my house, I bought a 48" double drum sander that had a 7 1/2 hp single phase motor. When I would turn it on (startup only), every light and appliance in the entire house would dim or pull down slightly. That motor was pulling so many amps on startup that it was causing a voltage drop in the 200 amp service lines supplying our house.

Mike Henderson

09-13-2008, 7:59 PM

I am pretty good at algebra, but I am having trouble seeing how theory translates into reality.

My first question is, why does a 220v circuit require 2 breakers? If amperage were the only issue in wire size, 1 should suffice.

Second, is the improvement people see in their performance when rewiring for 220v a result of that tool being on a dedicated and adequately wired circuit? I have always suspected that the reason for "lights dimming" is a circuit that is overloaded and drawing power away from the rest of the location (but not quite tripping the breaker). However, IANAE, although IAAL for what that is worth.
The reason you need two breakers on a 220V circuit has to do with the way the residential distribution system works. The power that comes into your home comes from the secondary of a center tapped transformer. The voltage between the outside wires of that secondary and the center is 110V and the voltage between the two outside wires is 220V.

In the USA, that center tap line is grounded. So any 110V circuit only has one wire that is at a potential to ground (110V). Since the second wire is connected to ground, the potential difference between it and ground is very small (should be zero).

So, for protection, you only need to fuse (or break) the "hot" lead.

But when you have 220V, both of your wires have a potential to ground - 110V. If you only had one circuit breaker, it would break the circuit but you'd still have 110V between that second wire and ground. Your machine would not run because no current could flow through the circuit.

Just as an aside, note that in the US, the voltage to ground on a 220V circuit is only 110V. To get shocked with 220V, you have to grab both wires of the circuit. Of course, 110V can kill you, but it won't kill you any faster on a 220V circuit than on a 110V circuit.

So - for safety - two breakers are required on a 220V circuit and they must be tied together so that if only one trips (such as if you grounded one of the wires) the other breaker will also trip and all voltage will be removed from your equipment.

For your second question - it's impossible to say for sure but the most likely cause is an improper circuit for the low voltage. When they switch to high voltage, they put in a new, properly designed circuit and the motor works like it should.

Mike

Mike Henderson

09-13-2008, 8:06 PM

Deleted this post.

Changed my mind.

Mike

Jim Becker

09-13-2008, 8:58 PM

Mike Henderson

09-13-2008, 10:35 PM

Mike, isn't the standard in the US now 120v and 240v? I know my power is 122v and 244v by actual measurement "as we speak". In fact, I had an issue last weekend with my slider shutting down when the voltage was running slightly higher. My conversations with Sam Blasco were interesting in that he had the same problem when he moved his shop...it was 239v at the old location and running 245v at the new one. (Buck/Boost transformer needed to correct)
You're right, Jim. I just use 110V and 220V by habit. The actual voltage is higher. I don't know what the utilities shoot for - at one time it was 117V but it could be 120V now.

But for what we're talking about, we could say "low voltage" and "high voltage" and still communicate okay.:)