# 20 amps at 110 volts Bandsaw



## Bluefilosoff (Mar 25, 2013)

I want to order a 17" bandsaw and I am concerned about whether it needs a dedicated outlet like an electric stove or dryer or can I just plug it into an ordinary outlet and go? 
The brochure says 20 amps at 110 volts or 10 amps at 220 volts? Any guidance greatly appreciated.


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## difalkner (Nov 27, 2011)

If it were mine I would wire it for 220 v *and* put it on a dedicated circuit. But definitely a dedicated circuit whichever way you go.


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## hwebb99 (Nov 27, 2012)

I'd wire it 220. Due to lack of space in in my breaker box I only have two 220 volt circuits shared between 3 tools. It really isn't a big deal.


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## Bluefilosoff (Mar 25, 2013)

Thanks, I guess what I'm explaining poorly is can I run a saw that big on a household plug? I run an old Sears contractor saw and a 6 " Laguna jointer on separate household plugs and I'm wondering if I could get away with that for a bigger bandsaw like I'm considering.


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## FrankC (Aug 24, 2012)

Do you have 20 amp 110 outlets wired into your shop, most ordinary outlets are 15 amp.

If not you will have to run a new line to run the saw, in that case you might as well run a 220 circuit.


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## Tennessee Tim (Dec 15, 2010)

Not necessarily.... some 110 circuits are wired for 15 amps. And yes for safety it would be best as a dedicated 20 amp circuit BUT BEST if wired 220. this saves electricity and is easier on the motor during starting and operating.


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## Bluefilosoff (Mar 25, 2013)

FrankC said:


> Do you have 20 amp 110 outlets wired into your shop, most ordinary outlets are 15 amp. If not you will have to run a new line to run the saw, in that case you might as well run a 220 circuit.


Ah I see now, unfortunately just 15 amp so yes time to call sparky. 

Cheers.


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## hwebb99 (Nov 27, 2012)

I doubt the saw would run on a 20 amp 110 volt breaker anyway. Have sparky wire it 220. It isn't that hard. You could probably do it yourself and save $.


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## Tony B (Jul 30, 2008)

DEpending on how far away your dryer outlet is, you can make a heavy duty extension cord and plug it in the dryer outlet when it is no being used. I did that for over a year and it worked out just fine. 
Just make sure you rewire your motor for the 220V. There should be a name plate on the motor with some specs and a wiring diagram to rewire the motor for 220. Very easy to do.


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## Bluefilosoff (Mar 25, 2013)

Tony B said:


> DEpending on how far away your dryer outlet is, you can make a heavy duty extension cord and plug it in the dryer outlet when it is no being used. I did that for over a year and it worked out just fine. Just make sure you rewire your motor for the 220V. There should be a name plate on the motor with some specs and a wiring diagram to rewire the motor for 220. Very easy to do.


Love this! 

Good old fashioned woodworker resourcefulness. In a pinch I will do this until I get a line put in. 
Thanks mang!


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## Steve Neul (Sep 2, 2011)

If it actually draws 20 amps on 110V you might have to put it on a dedicated line anyway. If you are at the saw for very long especially if you have anything else on the line running you shouldn't draw more than 16 amps on a 20 amp breaker. The general rule is to limit the draw to 80% of what the breaker is rated at. If it were me I would wire it to 220 but if that isn't an option I would change the wire to 10 gauge and install a 30 amp breaker.


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## GeorgeC (Jul 30, 2008)

hwebb99 said:


> I doubt the saw would run on a 20 amp 110 volt breaker anyway. Have sparky wire it 220. It isn't that hard. You could probably do it yourself and save $.


"You could probably do it yourself and save $" 

I do not think you should do this. Hire a professional. From your post it does not appear that work of this type in is your wheelhouse.

George


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## Tony B (Jul 30, 2008)

GeorgeC said:


> ................. i do not think you should do this. Hire a professional. From your post it does not appear that work of this type in is your wheelhouse..../QUOTE]
> 
> I totally agree with George. This is not meant to be a disparaging remark, but it is a humorous expression and mainly, it drives the point home.


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## ducbsa (Jul 6, 2014)

+1 on a new 220v circuit.

Regarding lower powered 110v tools, how often do you run more than one at once? Even in industrial power distribution design, if the motors aren't always running, the cable and fuses are sized for less than the motor nameplate amp total.


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## TimPa (Jan 27, 2010)

if the motor is dual voltage (110v/220v) then you have the choice to run the tool on the 110v/20amp circuit, or a 220v/10a circuit. 


a "typical" outlet circuit will have: 20 amp circuit breaker, 12 ga wire, and a 15 amp receptacle. after you verify the cb and wire, you should change the recep out for a 20 amp version to have a supply circuit capable of 20 amps for this tool.




Steve Neul said:


> If you are at the saw for very long especially if you have anything else on the line running you shouldn't draw more than 16 amps on a 20 amp breaker. The general rule is to limit the draw to 80% of what the breaker is rated at.


this is for branch circuits feeding _continuous_ loads, which are on for >3 hours time. not to say that you couldn't derate all branch ckts for an element of safety.


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## Steve Neul (Sep 2, 2011)

TimPa said:


> if the motor is dual voltage (110v/220v) then you have the choice to run the tool on the 110v/20amp circuit, or a 220v/10a circuit.
> 
> 
> a "typical" outlet circuit will have: 20 amp circuit breaker, 12 ga wire, and a 15 amp receptacle. after you verify the cb and wire, you should change the recep out for a 20 amp version to have a supply circuit capable of 20 amps for this tool.
> ...


That's all fine on paper but it makes a difference if you are aggravated by running back and forth to the breaker box resetting it. Putting a 20 amp saw on a 20 amp circuit is pushing limits.


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## Tony B (Jul 30, 2008)

Steve Neul said:


> .........Putting a 20 amp saw on a 20 amp circuit is pushing limits.


When in doubt, feel the wires, especially at the plug end. Slightly warm is not bad, but keep checking it. Hot is never good.
Also keep in mind that as the wires get warm, their electrical resistance gets higher. This results in even more warming. It becomes a system that feeds on itself. Either the wire, the fuse, the tool or all 3 are going die a painful death.

I still maintain that the safest cure is to use the 220V dryer outlet. That way when you pull the dryer plug, it cant be used at the same time as the saw. This is very safe. The only down side is the connecting and disconnecting of the new extension cord being a PITA. Then again, most woodworkers dont spend a lot of time on a band saw.

The plugs for the dryer outlet can be found in Walmart, Home Depot, Lowes and just about any hardware store. I havent bought any on a long time so I will guess the plug to cost around $15 or less these days.


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## TimPa (Jan 27, 2010)

a proper 20 amp circuit is designed to supply a 20 amp load safely, with no overload conditions. if the over current protection device is tripping, there is an issue with the device and it should be looked at for a problem.


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## Tony B (Jul 30, 2008)

Tony B said:


> When in doubt, feel the wires, especially at the plug end. Slightly warm is not bad, but keep checking it. Hot is never good.
> Also keep in mind that as the wires get warm, their electrical resistance gets higher. This results in even more warming. It becomes a system that feeds on itself. Either the wire, the fuse, the tool or all 3 are going die a painful death.
> 
> I still maintain that the safest cure is to use the 220V dryer outlet. That way when you pull the dryer plug, it cant be used at the same time as the saw. This is very safe. The only down side is the connecting and disconnecting of the new extension cord being a PITA. Then again, most woodworkers dont spend a lot of time on a band saw.
> ...


If your dryer is not in constant use, you might see about doing the same set-up for your Table saw, if it can be rewired for 220v also.

When you make the extension cord for the 220V you will be using a dryer plug at one end. I would strongly urge you to change the 110V ends of both the cord and the tool. There are less expensive 220v plugs both male and female that can be used at the tool end. This will elimate any chance of accidentally plugging a 220V plug into a 110V socket or outlet because the less expensive 220v plugs and recepticals will not fit in a 110v socket. The pin configuration is different.


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## ryan50hrl (Jun 30, 2012)

Steve Neul said:


> That's all fine on paper but it makes a difference if you are aggravated by running back and forth to the breaker box resetting it. Putting a 20 amp saw on a 20 amp circuit is pushing limits.



Putting a 20 amp saw in a home shop on a 20 amp circuit is by no means pushing it. That saw will rarely ever see full amp draw, and when it does, it will be for a short amount of time. 

I have all of my circuits in my shop sized correctly, 15 amp circuits with 15 amp or less tools and 20 amp circuits for 15-20 amp tools. The only time I've EVER popped a breaker is when I stalled my RAS in really thick oak. 

No ones hobby shop is ever going to have the tools running at 100% draw for hours on end. 

I'm a firm believer that running a 30 amp circuit when a 20 amp circuit meets the requirements is a waste of money.


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## ryan50hrl (Jun 30, 2012)

Tony B said:


> If your dryer is not in constant use, you might see about doing the same set-up for your Table saw, if it can be rewired for 220v also.
> 
> 
> 
> When you make the extension cord for the 220V you will be using a dryer plug at one end. I would strongly urge you to change the 110V ends of both the cord and the tool. There are less expensive 220v plugs both male and female that can be used at the tool end. This will elimate any chance of accidentally plugging a 220V plug into a 110V socket or outlet because the less expensive 220v plugs and recepticals will not fit in a 110v socket. The pin configuration is different.



You absolutely need to change the plug, and buy the correct one. A 20 amp plug should only be used on a 20 amp circuit. This ensures you always know what your plugging in to.


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## Alchymist (Jan 2, 2011)

TimPa said:


> if the motor is dual voltage (110v/220v) then you have the choice to run the tool on the 110v/20amp circuit, or a 220v/10a circuit.
> 
> 
> a "typical" outlet circuit will have: 20 amp circuit breaker, 12 ga wire, and a 15 amp receptacle. after you verify the cb and wire, you should change the recep out for a 20 amp version to have a supply circuit capable of 20 amps for this tool.
> ...





TimPa said:


> a proper 20 amp circuit is designed to supply a 20 amp load safely, with no overload conditions. if the over current protection device is tripping, there is an issue with the device and it should be looked at for a problem.


Does the brochure specifies a 20 amp at 120 volts circuit, or a draw of 20 amps at 120 volts. It the draw is truly 20 amps, it will not run on a 20 amp circuit - the instantaneous start current will pop a 20 amp breaker. If it specifies running it on a 20 amp circuit, then the nominal draw will be less.


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## hwebb99 (Nov 27, 2012)

ryan50hrl said:


> Putting a 20 amp saw in a home shop on a 20 amp circuit is by no means pushing it. That saw will rarely ever see full amp draw, and when it does, it will be for a short amount of time. I have all of my circuits in my shop sized correctly, 15 amp circuits with 15 amp or less tools and 20 amp circuits for 15-20 amp tools. The only time I've EVER popped a breaker is when I stalled my RAS in really thick oak. No ones hobby shop is ever going to have the tools running at 100% draw for hours on end. I'm a firm believer that running a 30 amp circuit when a 20 amp circuit meets the requirements is a waste of money.


 This is pushing it. I'd be surprised if the saw can even start if it truly pulls 20 amps.


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## hwebb99 (Nov 27, 2012)

GeorgeC said:


> "You could probably do it yourself and save $" I do not think you should do this. Hire a professional. From your post it does not appear that work of this type in is your wheelhouse. George


 Changing a motor over to 220 is easy. Unless you are a complete noob, there is no need to hire a professional. There is more involved in adding a 220 circuit. Although I have done it, I would recommend hiring a professional.


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## jdonhowe (Jul 25, 2014)

> BUT BEST if wired 220. this saves electricity and is easier on the motor during starting and operating.


 I must respectfully disagree. The motor (wired appropriately) can't tell the difference between 20 amps at 120 V and 10 amps at 240 V; It uses the same amount of energy regardless. 

The only real advantage of using a 15 amp circuit (either 120 or 240 V) is that you can get by with cheaper 14 gauge wire, whereas with a 20 amp (either 120 V or 240) circuit you need 12 gauge. One downside of 240 is that you need two slots in your panel, instead of one for a 120 circuit, and 2 pole (240 V) breakers are more expensive than 120.

I'd say if you already have a 20 amp 120V circuit in your work area, just use it. I assume you don't have a 240 line already installed, or you wouldn't be asking. If, down the road, you need 240 for a 240 only tool (e.g. big dust collector), you can have it wired sufficiently large to add the saw on as well.


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## ryan50hrl (Jun 30, 2012)

hwebb99 said:


> This is pushing it. I'd be surprised if the saw can even start if it truly pulls 20 amps.



I have every 15 amp rated tool in my shop on a 15 amp circuit, and every 20 amp took on a 20 amp circuit. Tools built from 1956 to 2015 and none of them have ever had a problem running on the correct circuit.


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## ryan50hrl (Jun 30, 2012)

By the way.....ratings exist for a reason. They're the safe operating standards of the system, they weren't determined by some chucklehead in a marketing department, they were determined by engineers and scientists based on actual data. 

If the standard was that 14 gauge wiring could only handle 12 amps, that's what the standard would be.


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## hwebb99 (Nov 27, 2012)

That was a full load rating. The starting load is much higher. If you overloaded the tool, the load is much higher. My bandsaw pulls 16 amps, and I have tripped a 20 amp breaker.


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## ryan50hrl (Jun 30, 2012)

I've never seen a tool that didn't have an issue that wouldn't run on the rated circuit. How old is your bandsaw?


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## Pirate (Jul 23, 2009)

If you look in the breaker box, at the 240 v breakers for the dryer, you will see just how 2 new breakers need to be installed and wired. 
The wire goes to the outlet. Very simple. I recently put in 2, 240 lines for a new AC install in our house.
Then again, "a man has to know his limitations" 
If you are not comfortable, don't do it.
I had a friend who rewired his whole house, and had it inspected. No problems.


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## hwebb99 (Nov 27, 2012)

Pirate said:


> If you look in the breaker box, at the 240 v breakers for the dryer, you will see just how 2 new breakers need to be installed and wired.
> 
> The wire goes to the outlet. Very simple. I recently put in 2, 240 lines for a new AC install in our house.
> 
> ...



My dad and I wired his whole house when it was built and passed inspection.


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## Alchymist (Jan 2, 2011)

Don't understand what the big deal is about someone wiring their house and "it passed inspection". What passed in one location may not pass in another. And inspectors have been known to miss things. Having done so does not make one an electrician. Just saying. YMMV.


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## hwebb99 (Nov 27, 2012)

Alchymist said:


> Don't understand what the big deal is about someone wiring their house and "it passed inspection". What passed in one location may not pass in another. And inspectors have been known to miss things. Having done so does not make one an electrician. Just saying. YMMV.



You're saying someone who wired a whole house and passed inspection is incapable of changing a motor from 110 to 220?


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## Alchymist (Jan 2, 2011)

hwebb99 said:


> You're saying someone who wired a whole house and passed inspection is incapable of changing a motor from 110 to 220?


Not what I said at all. Never intimated who was or wasn't capable of doing any electrical task. Just commenting that just because someone did a certain job and got through it doesn't make him an electrician.


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## Steve Neul (Sep 2, 2011)

Still arguing this topic? Go ahead and plug the saw in the outlet. Keep an eye on the motor temperature and the breaker will tell you if it will work or not.


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## Jig_saw (May 17, 2015)

Steve Neul said:


> Still arguing this topic? Go ahead and plug the saw in the outlet. Keep an eye on the motor temperature and the breaker will tell you if it will work or not.



I agree with Steve. 20A @ 120V is no big deal. I guess your circuit breaker is 30A. Here in India we use 15A @240V circuit breaker for power hungry appliances.


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## woodnthings (Jan 24, 2009)

*You have no idea...*



Jig_saw said:


> I agree with Steve. 20A @ 120V is no big deal. I guess your circuit breaker is 30A. Here in India we use 15A @240V circuit breaker for power hungry appliances.


To have a circuit rated at 20 AMPs at 120 V is the maximum that no. 12 GA wire will handle AND you will need a 20 AMP rated receptacle. You will rarely, if ever find a 30 AMP breaker on a 120 V circuit.

It is a big deal.:surprise2: You can NOT compare a 15 AMP 240 V circuit to a 20 AMP 120 V circuit in any way.

The higher the voltage, the lower the current draw in motors. Watts is watts and there's no way around it. Watts equals VOLTS X AMPs. One watt is equal to 1/746 HP. One HP is equal to 746 watts. A one HP motor typically draws 12 AMPs on 120 Volts at run condition.


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## Jig_saw (May 17, 2015)

*Maybe it is you who has to read physics again*



woodnthings said:


> To have a circuit rated at 20 AMPs at 120 V is the maximum that no. 12 GA wire will handle AND you will need a 20 AMP rated receptacle. You will rarely, if ever find a 30 AMP breaker on a 120 V circuit.
> 
> It is a big deal.:surprise2: You can NOT compare a 15 AMP 240 V circuit to a 20 AMP 120 V circuit in any way.
> 
> The higher the voltage, the lower the current draw in motors. Watts is watts and there's no way around it. Watts equals VOLTS X AMPs. One watt is equal to 1/746 HP. One HP is equal to 746 watts. A one HP motor typically draws 12 AMPs on 120 Volts at run condition.



Heating produced in a wire has to do with it's resistance times square of the current. For a given resistance, heating increases with the square of the current. However, Ohm's law relates voltage to be the product of the current and the resistance. Therefore, the rate of heating (i.e., power) has to do with the product of current and voltage. Thus [email protected] will produce exactly the same heating in any given wire as [email protected]. Your 30A fuse wire will have the same gauge as our 15A fuse.


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## Alchymist (Jan 2, 2011)

Jig_saw said:


> Heating produced in a wire has to do with it's resistance times square of the current. For a given resistance, heating increases with the square of the current. However, Ohm's law relates voltage to be the product of the current and the resistance. Therefore, the rate of heating (i.e., power) has to do with the product of current and voltage. Thus [email protected] will produce exactly the same heating in any given wire as [email protected]. Your 30A fuse wire will have the same gauge as our 15A fuse.


Not sure what that was all about, but:

The bottom line is that wire and breaker size is all about getting the most power to a load with the least voltage drop for the least cost.

A 120 volt 20 amp #12 wire circuit is the most common circuit across the country. 120 volt 15 amp #14 wire circuits are mostly for lighting. (One reason for not installing the 15 amp circuits for receptacles if that someone is sure to come along and plug in a heater, toaster, whatever).

Anyway, the desired result is to deliver power to the load with (usually) no more than a 3% voltage drop. Thus a 20 amp #12 circuit is the minimum desirable for a workshop, or for that matter, residential outlets. This will handle most domestic appliances, and in the shop most hand power tools as well as the smaller table saws, jointers, planers, etc, up to about a 2HP or so limit.

Now, if the run is long, (and this applies to any 120 or 240 volt circuit) at some point the voltage drop will exceed 3%, and the solution is to either increase wire size, or increase the voltage. If a 120 volt load can be switched to 240, then that's one solution, which requires only a different breaker. However this can only be done if it is not a circuit with a number of outlets.

If, however, the circuit in question is already a 240 Volt circuit, an increase in wire size is the only practical solution. An example here would be a 3HP compressor being replaced by a 5 HP model. 

Bear in mind also, as the current requirements increase a number of different connection requirements come into play.


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## jdonhowe (Jul 25, 2014)

> To have a circuit rated at 20 AMPs at 120 V ... you will need a 20 AMP rated receptacle.


 Sorry, not true; as long as you have more than a single receptacle, you can use 15 amp receptacles on a 20 amp circuit. It's very common in residential wiring, particularly with kitchen circuits. BTW, a duplex receptacle counts as more than one, so a single 15 amp receptacle is okay.


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## TimPa (Jan 27, 2010)

jdonhowe said:


> Sorry, not true; as long as you have more than a single receptacle, you can use 15 amp receptacles on a 20 amp circuit. It's very common in residential wiring, particularly with kitchen circuits. BTW, a duplex receptacle counts as more than one, so a single 15 amp receptacle is okay.



a 15 amp receptacle is not rated at 20 amps. my statement is true. can a 15 amp receptacle be used in a general purpose ckt? yes. 


however a 20 amp circuit for a 20 amp load should have all 20 a rated components. my opinion.


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## Jig_saw (May 17, 2015)

To original poster:


Have you tried plugging the saw and starting it? You can hook up a multimeter in the ammeter mode and check the AC current drawn by the saw. This will verify whether it is really [email protected] 110V.


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## Jig_saw (May 17, 2015)

Alchymist said:


> Not sure what that was all about, but:
> 
> The bottom line is that wire and breaker size is all about getting the most power to a load with the least voltage drop for the least cost.


My point is that whatever wiring is required for 110V @ 20A can also be used for [email protected] 10A. There is no change in wire thickness required for a given load (resistance). 

In India, we have a thinner wire gauge for lighting circuit ([email protected]) and heavier gauge for power circuit ([email protected]). Correspondingly, the circuit breaker for 120V should be 30A for running power appliances.


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## woodnthings (Jan 24, 2009)

There is no NEMA receptacle for a 30 AMP 120 V, 2 wire circuit.

I use the L6-20R for my 20 AMP 240V tools.
http://www.nooutage.com/nema_configurations.htm


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## Steve Neul (Sep 2, 2011)

woodnthings said:


> There is no NEMA receptacle for a 30 AMP 120 V, 2 wire circuit.
> 
> I use the L6-20R for my 20 AMP 240V tools.
> http://www.nooutage.com/nema_configurations.htm


Technically a person could wire a three wire 30amp receptacle omitting the earth ground. It was done all the time before the era of safety Nazi's. The two wire receptacle was just phased out because it wouldn't pass any new construction codes anywhere.


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## Alchymist (Jan 2, 2011)

woodnthings said:


> There is no NEMA receptacle for a 30 AMP 120 V, 2 wire circuit.
> 
> I use the L6-20R for my 20 AMP 240V tools.


It's shown in your chart....

http://www.cooperindustries.com/content/dam/public/wiringdevices/BuyersGuides/RBG/B/RBG-B-Sec-41.pdf


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## woodnthings (Jan 24, 2009)

*I don't see one....*

Quote: There is no NEMA receptacle for a 30 AMP 120 V, 2 wire circuit.



Alchymist said:


> It's shown in your chart....
> 
> http://www.cooperindustries.com/content/dam/public/wiringdevices/BuyersGuides/RBG/B/RBG-B-Sec-41.pdf



There is none for* 120V* - 2 wire that I see.:nerd2:


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## Alchymist (Jan 2, 2011)

woodnthings said:


> Quote: There is no NEMA receptacle for a 30 AMP 120 V, 2 wire circuit.
> 
> 
> 
> ...


If you are talking an outlet without ground, true. But why would you even want a 120v 30 amp receptacle without a ground???


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## d_slat (Apr 10, 2012)

Jig_saw said:


> Heating produced in a wire has to do with it's resistance times square of the current. For a given resistance, heating increases with the square of the current. However, Ohm's law relates voltage to be the product of the current and the resistance. Therefore, the rate of heating (i.e., power) has to do with the product of current and voltage. Thus [email protected] will produce exactly the same heating in any given wire as [email protected]. Your 30A fuse wire will have the same gauge as our 15A fuse.


Ohms law does not apply to the heating of a conductor like you are trying to describe here, since you won't see 120 or 240 volt drop across the conductor. Current is what heats the conductor, so 20a at 120v or 240v will produce the same heat in the conductor.


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## Tony B (Jul 30, 2008)

d_slat said:


> Ohms law does not apply to the heating of a conductor like you are trying to describe here, since you won't see 120 or 240 volt drop across the conductor. Current is what heats the conductor, so 20a at 120v or 240v will produce the same heat in the conductor.


Not quite, if we are talking the SAME circuit. 
If a tool pulls 20A @120V, the same tool will pull only 10A at 220V. 
The 20A running through a 12Ga wire will be warmer than 10A running through the same 12 ga wire. 
With the higher current in the 120V circuit, we will also have a higher temp resulting in a higher resistance which will turn into a higher voltage drop reducing the efficiency of the 120V circuit. This gets compounded by the motor surge current also. 
If an electrician were to wire a new 220V circuit he will most likely use at least a 10 ga wire and further decrease the line voltage drop resulting in better starting and running. 
Your electric bill will not reflect these factors because they are usually minute changes and for short durations. 


Bottom line is that if you used the same wires in your wall and changed the voltage from 120 to 240, you will be drawing only half the current.


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## ryan50hrl (Jun 30, 2012)

Guys....the theory of electrical engineering is all fine and well, but it's not practical in this setting. Standards and norms exist for a reason, use them. Electricians are not going to use 10 gauge wiring for a 15 amp 220 circuit, it's not necessary....period. 

Anyone receiving advise should be getting advice based on industry standards, not what your uncle frank told you, or what makes you feel good. Leave theory to scientists and engineers, build your shops based on standards.


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## mat 60 (Jul 9, 2012)

Man..Is there anything that doesn't turn a pissing match here..LOL


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## ryan50hrl (Jun 30, 2012)

Just electrical, import tools, beer, and politics.


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## Shop_Rat (Dec 22, 2015)

You need woodworking advice? Go to a woodworking site. You need electrical advice? Go to an electrical site.

Too many folks THINK they know more than they actually do...


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## Steve Neul (Sep 2, 2011)

I real reason the electric topic gets heated is nobody, not even electricians can agree. I've seen all to many electricians argue with each other.


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## ryan50hrl (Jun 30, 2012)

It's true, and somehow in this modern age when actual data and research is available like never before in history, people are becoming less and less likely to actually do research. 

I'd suspect if this argument were taking place in the 1950's equivalent of this place, someone would have found a reference manual that quoted actual codes and standards. Today, I'm finding in many things people prefer to take the word of random strangers as fact.


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## ryan50hrl (Jun 30, 2012)

Like for example, that 14 gauge wiring will handle 15 amps just fine....


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## ryan50hrl (Jun 30, 2012)

By the way....if anyone wants the most useful book on earth....check it out.


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## Alchymist (Jan 2, 2011)

ryan50hrl said:


> By the way....if anyone wants the most useful book on earth....check it out.
> 
> View attachment 232634


Those come in several different versions. Someone made off with my mechanical version, but still have the electrical/electronic/computer version.


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## Tree Hugger (Sep 1, 2011)

I got nothing to add that hasn't been said ...so some random thoughts.


Back in the stone age when I took some course work in the electrical field the instructor said that with the nuclear power plants coming on line, electricity would be so cheap that they wouldn't even meter it.
How's that working out for everyone?


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## d_slat (Apr 10, 2012)

Tony B said:


> Not quite, if we are talking the SAME circuit.
> If a tool pulls 20A @120V, the same tool will pull only 10A at 220V.
> The 20A running through a 12Ga wire will be warmer than 10A running through the same 12 ga wire.
> With the higher current in the 120V circuit, we will also have a higher temp resulting in a higher resistance which will turn into a higher voltage drop reducing the efficiency of the 120V circuit. This gets compounded by the motor surge current also.
> ...


Absolutely correct. but go back and read the post I was correcting and what I wrote. The point I'm trying to relay is that 20 amps at 120, or 20 amps at 240 will produce the same heat in the same size conductor.


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## Steve Neul (Sep 2, 2011)

ryan50hrl said:


> Like for example, that 14 gauge wiring will handle 15 amps just fine....
> View attachment 232626


This is where you and I will always disagree. Too many electricians are using 14 gauge wire for outlets. Yesterday I had to repair a fence using a smudgepot air compressor. I tried plugging it into the outside outlet by their front door and there was barely enough power there to make it try to start. I ended up having to carry the compressor around the house to the garage every time it needed to cycle. I'm sure someone thought, it's just an outside outlet all they will be using on it is Christmas lights.


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## Tony B (Jul 30, 2008)

Steve Neul said:


> ......... I'm sure someone thought, it's just an outside outlet all they will be using on it is Christmas lights.


Yes, and how much did they save off the total cost of the house by using lighter wire? :|


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## Tony B (Jul 30, 2008)

d_slat said:


> ......The point I'm trying to relay is that 20 amps at 120, or 20 amps at 240 will produce the same heat in the same size conductor.


Sorry, yes you are correct. I took it out of context because previously we were comparing the current from one particular motor on 120 vs. 240. My bad.


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## BZawat (Sep 21, 2012)

14AWG will handle 15 amps, yes. No problem. Residential "industry standard" is to run 14AWG for lighting circuits and 12 AWG for receptacle circuits.

A motor that draws 15 amps should be fed by a 20 amp circuit, or it will trip a breaker when the motor is under full load.


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## Chamfer (Sep 6, 2014)

Steve Neul said:


> This is where you and I will always disagree. Too many electricians are using 14 gauge wire for outlets. Yesterday I had to repair a fence using a smudgepot air compressor. I tried plugging it into the outside outlet by their front door and there was barely enough power there to make it try to start. I ended up having to carry the compressor around the house to the garage every time it needed to cycle. I'm sure someone thought, it's just an outside outlet all they will be using on it is Christmas lights.




I will be the first one in this thread to admit they do NOT know what they are talking about, I am just a lowly carpenter.

Can someone explain the following to me- We often run 50-100ft of 12g extension cord to where we are working on a job. We often have both my compressor and either my CS or MS both plugged in to that one cord. It's not uncommon to have the compressor cycling while someone is making a cut. My compressor is rated at 12A and both my CS and MS are rated at 15A. Why have I never tripped a breaker on a single 15 or 20A recepticle regardless of 14 or 12g wire used in the circuit?


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## ryan50hrl (Jun 30, 2012)

Think of it this way. A new truck today has somewhere around 350 horsepower. But you rarely use 100% of that power. Your most often probably only using 150 hp as you cruise down the highway.

Your saw and compressor are the same, accelerating both the saw and compressor motors from a dead stop to running at the same time likely would trip the breaker, but you rarely if ever do that. 

Also cutting 2x4 pine, or trim boards isn't very taxing on your saw. If you were trying to cut 4x8 hard maple, your saw would be working a lot harder.


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## Chamfer (Sep 6, 2014)

ryan50hrl said:


> Think of it this way. A new truck today has somewhere around 350 horsepower. But you rarely use 100% of that power. Your most often probably only using 150 hp as you cruise down the highway.
> 
> Your saw and compressor are the same, accelerating both the saw and compressor motors from a dead stop to running at the same time likely would trip the breaker, but you rarely if ever do that.
> 
> Also cutting 2x4 pine, or trim boards isn't very taxing on your saw. If you were trying to cut 4x8 hard maple, your saw would be working a lot harder.




Actually initial start ups at the same time happen more often than you might think. Probably not enough to say 'regularly', but I've seen it happen more times than I can count.

That aside, if the compressor is cycling, using IDK lets say half of the amperage it's rated for at initial start up, and I pull the trigger on my MS, I would think the initial 15A momentary draw from the saw along with the steady 6A'ish draw from the compressor would be enough to trip a 15-20A breaker. Or are all circuits made to handle momentary draws well beyond their ratings?


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## ryan50hrl (Jun 30, 2012)

Your counting on the initial start up as a second, or the moment you hear it. The initial startup draw happens so quickly your unable to register that time frame without equipment to monitor in fractions of a second.


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## Steve Neul (Sep 2, 2011)

Chamfer said:


> I will be the first one in this thread to admit they do NOT know what they are talking about, I am just a lowly carpenter.
> 
> Can someone explain the following to me- We often run 50-100ft of 12g extension cord to where we are working on a job. We often have both my compressor and either my CS or MS both plugged in to that one cord. It's not uncommon to have the compressor cycling while someone is making a cut. My compressor is rated at 12A and both my CS and MS are rated at 15A. Why have I never tripped a breaker on a single 15 or 20A recepticle regardless of 14 or 12g wire used in the circuit?


Think of electricity like it was water. If you were trying to use a 1/4" air hose for a garden hose you would have a lot of trouble getting the water you need. Then the farther you go with that undersized hose the worse the problem would be. It's not so much tripping the breaker but having enough power to do what you need. The electrons in electricity pass over the outside of the wire and the larger surface it has the power it will deliver. Then stranded wire conducts better power than solid copper because the electrons pass over each strand so it has more surface area. Apparently where you have been working you have been plugging in your extension cord into a good source of power. Your 12g stranded extension cord is also a lot better conductor than a 14g solid wire used in romex wire.


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## Tree Hugger (Sep 1, 2011)

Had to try out my kilo-watt meter on my delta contractor table saw 1.5 hp
Dedicated 20 amp 12 gauge circuit.
Heavy duty extension cord .
121 volts at the meter (at the end of the extension cord).
The meter flashed around 22 amps then 23 amps in quick succession and then 4.49 amp as it came to speed. 
Cutting a 1/2 piece of plywood the amps increased to around 6amps.
So even with capacitor start you still get a spike but a very short one and not enough to trip the breaker.
Light cuts and you will not draw the maximum rated amps of the unit.
Just because a breaker doesn't trip means your using safe practices.
I have a couple of circuits in my basement I've derated at the breaker ( #12 wire with 15 am breaker)..why ? 
So someone long after I'm gone doesn't overload the circuit..say like a continuous draw of a 15 amp space heater 
and god only knows what else they can think of ( treadmills , tvs ect).













*Allowable Breaker Load*



The National Electrical Code doesn't limit the number of receptacles you can place on a 20-amp circuit, but you'll overload the breaker if you run appliances that draw more current than the breaker can handle. The NEC does specify that a circuit breaker shouldn't handle more than 80 percent of the load for which it is rated unless the breaker is labeled otherwise. By this standard, the total current draw on a 20-amp circuit shouldn't exceed 16 amps. This allows the breaker to handle the temporary surge that happens when an appliance such as a power saw or air conditioner starts up.


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## Alchymist (Jan 2, 2011)

One reason that a breaker may not trip when using long extension cords is that the long wires act as series resistance and lower the voltage delivered to the load. As to breakers, they operate on a magnetic/time constant curve. Any current in excess of the rated current will "eventually" trip a breaker. A small overload may take many minutes to trip, and as the overload increases, the time to trip shortens. This is the reason the 20 amp circuit can supply very short duration currents of 25 or 30 amps or more. 

If you look at the charts tool manufacturers supply with most tools, the current and the distance both play a role in wire size. For example a tool that will run on a #14 extension cord at 25 feet or 50 feet may require a jump to a #12 wire at 100 feet to insure adequate voltage to the tool. Another thing often overlooked is the distance from panel to outlet. In a big shop this can be 40 or 50 feet or more, and adding an extension cord just further acerbates the voltage drop.

Personally I don't use #14 cords for any power tool, #12 may be overkill for a 1/4: drill, but not having a lighter cord around does tend to prevent grabbing one when using a larger tool.


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## Jig_saw (May 17, 2015)

d_slat said:


> Ohms law does not apply to the heating of a conductor like you are trying to describe here, since you won't see 120 or 240 volt drop across the conductor. Current is what heats the conductor, so 20a at 120v or 240v will produce the same heat in the conductor.



As I said in my post you are referring to, heating rate for a given load (resistance) is proportional to the square of the current times the resistance:


Heating rate = current x current x resistance


But Ohm's law relates the resistance as the ratio of voltage and current:


voltage = current x resistance


So the heating rate (by the virtue of Ohm's law) becomes the product of the voltage and the current:


Heating rate = current x voltage


which is what we understand by the 'power' flowing through the circuit.

If you read carefully, you will find both of us are saying exactly the same thing.


BTW, the reason an overload beyond 20A may not be tripping the breaker is because a factor of safety (1.5) is built-in. Thus I think what is labeled as a 20A breaker, is actually a 30A breaker.


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## GeorgeC (Jul 30, 2008)

If "google" stranded wire vs solid core wire you will find out that at 60hrts there is virtually no difference between stranded and solid core wire regarding resistance. The skin effect comes into play at much higher frequencies.

The main reason for using stranded wire is that in larger sizer it is more flexible.

George


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## d_slat (Apr 10, 2012)

Jig_saw said:


> If you read carefully, you will find both of us are saying exactly the same thing.


No, we're not. Your inclusion of ohms law into what we are talking about is dead wrong. Voltage has no significant affect on the heating of a conductor.

Edit: I think I see what you are trying to do, but it doesn't work the way you are thinking. If you want to substitute voltage into the equation for heating of the conductor instead of current x resistance, you have to use the voltage drop across the conductor at load, not the circuit voltage.


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## Alchymist (Jan 2, 2011)

Jig_saw said:


> As I said in my post you are referring to, heating rate for a given load (resistance) is proportional to the square of the current times the resistance:
> 
> 
> Heating rate = current x current x resistance
> ...


No, it's actually a 20 amp breaker. See chart below for how breakers work. A 30 amp breaker will have higher trip currents for the same time factor than a 20 amp. It is not a "safety factor".


GeorgeC said:


> If "google" stranded wire vs solid core wire you will find out that at 60hrts there is virtually no difference between stranded and solid core wire regarding resistance. The skin effect comes into play at much higher frequencies.
> 
> The main reason for using stranded wire is that in larger sizer it is more flexible.
> 
> George


Yes, and it's hard to convince people of this. They read it somewhere, and didn't notice or dont remember the part frequency plays in skin effect.



d_slat said:


> No, we're not. Your inclusion of ohms law into what we are talking about is dead wrong. Voltage has no significant affect on the heating of a conductor.
> 
> Edit: I think I see what you are trying to do, but it doesn't work the way you are thinking. If you want to substitute voltage into the equation for heating of the conductor instead of current x resistance, you have to use the voltage drop across the conductor at load, not the circuit voltage.


True, you can't use current at applied voltage to figure heat loss. Most of the power consumed is at the load, only a small portion is lost in heating the conductors. The only time when the heat in the conductor becomes a factor is when the wire is too small for the load current, and the heat is enough to damage the conductor.

When a conductor becomes appreciably warm to the touch, not only is it too small, but it is causing more heat buildup in any motor it's supplying. Not a factor in resistive loads, just a loss of efficiency.


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