changing tools to 240V - power cord question

[dunk6666]

I want to convert my band saw and jointer to use 240 volts. I have the wire diagram for the motors and have no questions on that. The manual says that for 120 v, I should use a 5-20 plug, which is what it came with. For 220 v, it says to use a 6-15 plug. My 220 circuit is 20A so I will use a 6-20 plug. The power cord on the band saw is made up of 16 gauge wire, according to the spec sheet. If, when running on 120v, it recommended a 20 A circuit, why does it have a 16 Gauge cord on it? I thought you needed a 12 gauge wire for a 20A circuit. Should I replace it when I get the new plug? And if I do replace the power cord, what do I replace it with? It obviously can’t just be a piece of romex and I doubt it would be an ‘extension cord’.


Thanks

Eric

 

[LigouriRd]

Assuming that the tool was designed properly from the factory, the wire was probably spec'ed out to meet the current draw of the tool based on whatever electrical standard the manufacurer certifies to. 16Ga stranded has a higher carrying capacity than solid (romex, etc.).
I would think the 16ga wire would be fine, there will be less amps drawn at 220v anyway (20A@120V = 11A@220V)

 

[Stuart in MN]

If they run fine now on the existing cord at 120vac, they will be fine at 240vac. The 12 gauge wire for 20 amp circuit requirement is in the NEC, which covers the building wiring - power cords on tools are covered under different standards.

I'll ask if there's a specific reason you want to convert them to 240vac...if they run fine now on 120vac, there's no particular advantage in converting them.

 

[dunk6666]

If they run fine now on the existing cord at 120vac, they will be fine at 240vac. The 12 gauge wire for 20 amp circuit requirement is in the NEC, which covers the building wiring - power cords on tools are covered under different standards.

I'll ask if there's a specific reason you want to convert them to 240vac...if they run fine now on 120vac, there's no particular advantage in converting them.

Stuart - I have read that the motors will last longer. Plus they draw a lot of amps on my 120 circuits.

Eric

 

[rlitman]

They will not last any longer. Your sources are wrong.

More amps does not equal more power. The power draw is the same, so how much you pay is still the same.

 

[Alchymist]

One of the major factors in conductor size is voltage drop. In your case, the original wire is fairly short, so voltage drop is minimal. Also, the size of the plug/receptacle is not directly tied to the demands of the machine. I doubt your band saw will draw 15 amps on 240V. Check the motor data plate for more information.

 

[Charles (in GA)]

Assuming that the tool was designed properly from the factory, the wire was probably spec'ed out to meet the current draw of the tool based on whatever electrical standard the manufacurer certifies to. 16Ga stranded has a higher carrying capacity than solid (romex, etc.).
I would think the 16ga wire would be fine, there will be less amps drawn at 220v anyway (20A@120V = 11A@220V)

True, but it only is measurable, or having any noticeable effect under, if I recall, very high frequencies and voltages. given 60hz 120 or 240 v current, there will be no measurable difference in current carrying capacity of fine stranded vs solid. (even difficult to meausure under laboratory conditions, if even then).

Charles

 

[sberry]

If it came with a factory 16 cord I agree no real advantage to changing. If this is a single use circuit it adds to the cost, uses another breaker space and may have issues with sizing these type of circuits.
This is a real good case for not messing with it unless you have to.

 

[wyliesdiesels]

Stuart - I have read that the motors will last longer. Plus they draw a lot of amps on my 120 circuits.

Eric

The only advantage to using higher voltage is the ability to use smaller gauge wire since current is reduced. This has huge savings potential when it comes to large motors that draw a LOT of current even on 480v!

In your case, the smaller size of wire needed at higher voltage doesnt matter since your tools dont draw that much to begin with!

 

[Charles (in GA)]

Woodworkers claim that 240v equipment starts smoother and runs smoother on 240v than on 120v given a multi-voltage motor.

Charles

 

[dunk6666]

I am not claiming to be an expert, but i have seen similar thoughts such as this:

"since you have two wires carrying half of the amps, the wear on the switches are less, the voltage drop is less, the lights dim less, and it balances the electrical load. There is less heat, and wear on the motor it self. There is faster recovery from bogging under heavy load and less bogging in general, which is an advantage in thicker materials."

Regardless, my 240 circuits are dedicated for my larger tools and my 120 lines are shared amongst my smaller tools. My jointer draws 15 amps at 120 and I don't want that to interfere with other things running on the 120 circuit.

Eric

 

[rlitman]

Whether 120V or 240V, both wires carry the full current of the circuit.
Yes, at twice the voltage, the amperage is halved.
Yes, at 240V, you will get less dimming of lights.
No, the motor heating is identical. No, the motor wear is identical. No, motor bogging would only be different if your wiring were inadequate. No motor recovery to speed would be identical, this is a function of horsepower, not the wiring.

How many people work in your shop? I have dedicated circuits for things that could be used at the same time. Air compressor, dust collection, lights. Power tools are on a shared circuit. I'm not going to be using the grinder/table saw/chop saw/drill press, etc. all at the same time.

I do use the plasma cutter at the same time as the air compressor, so they're not on the same circuit. Same thing goes for saws and dust collection (or the compressor and dust collection when I'm using pneumatic sanders). Lights are always on a dedicated circuit (ok, I share them with the TV), so they don't go out when a tool binds up and trips a breaker. I also have a separate circuit for my freezer.

If you just want dedicated circuits, then run them. But switching to 240V for the sake of using 240V on individual tools is pointless (and this, coming from someone who tries very hard to run as much equipment at work on 208V instead of 120V whenever possible).

 

[2ManyProjects]

I want to convert my band saw and jointer to use 240 volts. I have the wire diagram for the motors and have no questions on that. The manual says that for 120 v, I should use a 5-20 plug, which is what it came with. For 220 v, it says to use a 6-15 plug.

So far, so good.

My 220 circuit is 20A so I will use a 6-20 plug.

You just de-railed.

While there may be some justification for using a 6-20R receptacle in the outlet box (tho' very little justification, if the outlet will be dedicated to that tool), there is NO good reason to use a 6-20P on the tool itself, since it will ALWAYS draw (much) less than 15 amps @ 240V. Note that if you compare the two plug/socket types:

http://upload.wikimedia.org/wikipedia/commons/0/0d/NEMA_simplified_pins.svg

You will see that the 6-15P WILL fit into the 6-20R.

The power cord on the band saw is made up of 16 gauge wire, according to the spec sheet. If, when running on 120v, it recommended a 20 A circuit, why does it have a 16 Gauge cord on it? I thought you needed a 12 gauge wire for a 20A circuit.

As others have pointed out, the "official" requirement to use AWG 12 (or heavier) for a 20A circuit is limited to permanently installed wiring. Plug-in power cords on (even nominally) "portable" devices are not covered by those regulations/standards.

That said, AWG 16 DOES seem somewhat on the light side for that application, by my lights, particularly if the power cord is more than a foot or two long.

Should I replace it when I get the new plug?

If that same AWG 16 cord worked OK at 120V, it will surely work OK (even better, really) at 240V, since it will now need to carry only half as much current to power the tool. So the short answer is, you probably don't NEED to replace the cord. But if you WANT to replace it with something a bit heavier, it surely won't hurt. The only cautionary note I'll sound is to make sure that wherever the cable connects inside the tool, the terminals will correctly accommodate the heavier wire.

And if I do replace the power cord, what do I replace it with? It obviously can’t just be a piece of romex and I doubt it would be an ‘extension cord’.

Actually, you very probably could cannibalize an old extension cord, if it was of adequate AWG and had the right sort of plug on it; but that probably would not be cost-effective if the extension cord is otherwise usable as-is. Ideally, you'd want some 3-conductor Type SOOW cord, of at least AWG 16 (but since most of the point of replacing the cord is to upgrade it, make that AWG 14 or heavier)

Systek P/N: 10523 would be suitable.

http://www.systekcable.com/wire/product_info.php?cPath=68&products_id=276

Or Omni B11403 / B11403-V:

http://www.onestopbuy.com//wire-cable/B11403-40198.asp?pt=frB11403

http://www.onestopbuy.com//wire-cable/B11403-V-42014.asp?pt=frB11403-V

Or, something like this

http://www.americord.com/6-15p-to-roj-2in-strip-1-4in.html

would also likely do the trick.

Assuming that the tool was designed properly from the factory, the wire was probably spec'ed out to meet the current draw of the tool based on whatever electrical standard the manufacurer certifies to. 16Ga stranded has a higher carrying capacity than solid (romex, etc.).
I would think the 16ga wire would be fine, there will be less amps drawn at 220v anyway (20A@120V = 11A@220V)

True, but it only is measurable, or having any noticeable effect under, if I recall, very high frequencies and voltages. given 60hz 120 or 240 v current, there will be no measurable difference in current carrying capacity of fine stranded vs solid. (even difficult to meausure under laboratory conditions, if even then).

Charles

Correct, sort of.

It's not even really a matter of "current carrying capacity", per se; but rather, stranded wire will exhibit somewhat less attenuation of VERY high-frequency (measured in MegaHertz, or at least dozens/hundreds of KiloHertz) signals than solid-core wire will. At 60 Hz, it is simply a non-issue.

I am not claiming to be an expert, but i have seen similar thoughts such as this:

Taking these "thoughts" one-by-one...

"since you have two wires carrying half of the amps, the wear on the switches are less,

Wrong. Wear on the switch contacts will be almost purely a matter of their mechanical properties vs. how often/roughly they are cycled. Higher-quality switches will last longer than cheap crappy switches.

OTOH, the higher voltage potential across the switch contacts MIGHT actually exacerbate wear, if it leads to (more) arcing.

the voltage drop is less,

True. HOWEVER, whether or not this will be significant in any given case depends on more variables than we have available here at the moment.

the lights dim less,

Maybe, but probably not IF the building's electrical service is adequate and the wiring is designed and installed correctly. Your lights should not be on the same branch circuit(s) as your power tools (especially your BIG power tools). So if the lights are dimming AT ALL when you kick on one of those big machines, that implies that you're somehow dragging down the main feed to the sub-panel/building. If that is the case, the CORRECT cure is to upgrade the building's electrical service & wiring, not try to "skate by" by re-jiggering your tools to use slightly less current. In short, you'd be treating the symptom, instead of curing the disease.

and it balances the electrical load.

This depends on how "unbalanced" is is now, and why. In practice, it really shouldn't matter.

There is less heat, and wear on the motor it self.

Probably untrue -- or at least "mostly" untrue. While you are cutting the current in half, you are doubling the voltage; so exactly the same amount of POWER is being consumed. It is power which most closely correlates to heat. IF the tool's internal wiring & such is inadequate, so that the higher current flow at 120V causes significantly more voltage drop, then going to 240V might somewhat ameliorate this; but then, this should NOT be the case in the first place, so...

There is faster recovery from bogging under heavy load and less bogging in general, which is an advantage in thicker materials."

Again, probably untrue, or at least "mostly" untrue, for most of the same reasons as in the previous answer, and again presuming that the building's electrical service and wiring are up to snuff.

Regardless, my 240 circuits are dedicated for my larger tools and my 120 lines are shared amongst my smaller tools. My jointer draws 15 amps at 120 and I don't want that to interfere with other things running on the 120 circuit.

Now THAT is actually a good reason to convert the stationary tools to 240V. .

 

[theoldwizard1]

My experience has been 6-20 plugs and receptacles are more common than 6-15.

For short length of cord/wire the following is pretty much irrelevant.

The voltage drop across a piece of wire is determined by Ohm's Law, E=I*R. The resistance (R) of a given length of wire (typically obtained from a table) is constant, so when you cut the current (I) in half (by doubling the supply voltage) the voltage drop is cut in half.

So if you have a 120V load (motor) that is operating near the limit of the circuit breaker, changing it to 240V operation (and changing the circuit breaker) would half the current draw and the voltage drop ! (Of course, anything else on that circuit would have to be rewired for 240V).


Most of the "rest of the world" uses 240V so they can use less copper (and maybe a bit more insulation) in their wiring.

Automaker had a big push in the 1980s to go to 36V (42V charging). Big cost and weight savings in wiring and motors. It was deemed too difficult to get every single component from the smallest light bulb to the starter, alternator and battery converted at the same time. 36V lead acid battery (still the most cost effective battery chemistry for high current) were a real problem because the case and internal cell dividers could not be made any smaller. So a 36V battery in the same footprint had a lot less power and cost more to make.

 

[justsam]

Automaker had a big push in the 1980s to go to 36V (42V charging). Big cost and weight savings in wiring and motors.

So does this mean I can toss out all the SAE "white papers" I have squirreled away on 42V, or save them for yet another "STANDARD" that never was!

 

[wyliesdiesels]

I am not claiming to be an expert, but i have seen similar thoughts such as this:

"since you have two wires carrying half of the amps, the wear on the switches are less, the voltage drop is less, the lights dim less, and it balances the electrical load. There is less heat, and wear on the motor it self. There is faster recovery from bogging under heavy load and less bogging in general, which is an advantage in thicker materials."

Regardless, my 240 circuits are dedicated for my larger tools and my 120 lines are shared amongst my smaller tools. My jointer draws 15 amps at 120 and I don't want that to interfere with other things running on the 120 circuit.

Eric

Keep in mind, watts is watts. 10a @ 240v is 2400w and 20a @120v is, u guessed it, 2400w!! As someone already said, watts is what is gonna cause heat issues along with high resistance!!