Extensions Cords

[nickao]

I normally always purchase 12/3 cords that are lighted with 3 receptacles at the end. I dont even own cords less than 12/3, not even my shorter 15 foot cords. Recently I needed a lot of longer cords and though I have a couple 12/3 100 and half a dozen each 12/3 - 50 and 25 footers what are the thoughts on the 10/3 cords. Are 10/3 cords really needed? Both 10/3 and 12/3 are rated 15 amps on the packaging. It seems to me those 10/3 cords can easily handle 20 amps, some come with the 20 amp ends, most don't.

Is there a reason to spend the extra money on 10/3 cords of any length? We never had them on the job site ever. For arguments sake lets assume something like an OF2200 or a tool that will pull near the 15 amp is going to be used on the USA 120V system.

 

[RussellS]

Not sure about your amp ratings for 12 and 10 gauge cords.  I think they are wrong.  But the big thing you seem to be missing is the length aspect.  If for some reason you are running your extension cords 200 feet, then you need 10 gauge at least.  If you tried to attach all your 12 gauge cords together to make it 400 feet for example, you could not use many amps at the plug end.  Whereas if you did the same using 10 gauge cords, you could run a bigger tool at the end.  10 gauge is needed if you need a big tool over a short distance, or a medium tool over long distance.  12 and 14 gauge cords work the same way, but you have to lower the size of the tool in all cases.

For me 12 gauge works perfectly fine.  I have a few that add up to 100 or so feet.  I rarely ever need to go beyond 100 feet.  And all my electric tools work fine on 12 gauge at 100 feet.  None of my electrical tools are huge.  Drills, saws, routers.  I don't have those huge jack hammer tools breaking concrete.  Maybe I could put one of those jack hammer tools on my 12 gauge cords if I made it 10 feet long.  But not at 100 feet.

 

[Kev]

[member=3373]Dovetail65[/member] is this useful ?
http://buyextensioncord.com/info_voltage_drop.shtml

 

[rst]

I used to done storefront (8-10 jobs/year) work for a super market chain.  We used 150' of 10/3 that we kept rolled and a wooden spool and often had another 100' of 12/3 to get from the back to the front of the store.  This was so our 15 amp Makita chopsaws would not bog down.  I also did hydralic automatic door work for this same chain and often encountered mild shocks from the neutral wires suppling the pump motors.  Scared the bejesus out of me until an electrician explained that often the original wiring was not using heavy enough wire to carry the return voltage.  Pretty much the same as the electro-static charge from non-grounded dust collectors.

 

[nickao]

Not sure about your amp ratings for 12 and 10 gauge cords.  I think they are wrong.  But the big thing you seem to be missing is the length aspect.  If for some reason you are running your extension cords 200 feet, then you need 10 gauge at least.  If you tried to attach all your 12 gauge cords together to make it 400 feet for example, you could not use many amps at the plug end.  Whereas if you did the same using 10 gauge cords, you could run a bigger tool at the end.  10 gauge is needed if you need a big tool over a short distance, or a medium tool over long distance.  12 and 14 gauge cords work the same way, but you have to lower the size of the tool in all cases.

For me 12 gauge works perfectly fine.  I have a few that add up to 100 or so feet.  I rarely ever need to go beyond 100 feet.  And all my electric tools work fine on 12 gauge at 100 feet.  None of my electrical tools are huge.  Drills, saws, routers.  I don't have those huge jack hammer tools breaking concrete.  Maybe I could put one of those jack hammer tools on my 12 gauge cords if I made it 10 feet long.  But not at 100 feet.

I never go over a 100 feet, I totally understand the length. Even at a 100 feet I dont see why 10 gauge would be needed over 12 for a 15 amp tool. As far as wire on its own 12 gauge wire is definitely adequate for 15 amp and rated for 20 amp(14 gauge for 15 amp) and 10 gauge is rated for 30 amp. For extension cords possibly these rating are different than wire on its own?

All 12/3 cords I have found are rated for 15 amp, but I am finding a lot of the 10/3 extension cords are rated as 15 amp as well, which is confusing to me. I  think the 10/3 gauge may be rated at 15amp on the package only because they have the 15 amp ends and if they had the 20 amp ends the package could read 20 amp. I know for a fact my 220V 20 amp extension cords use 10 and 12 gauge wire as well.

I guess my question is over time if using a longer cord is the 10/3 going to give me anything or am I possibly getting a loss of power I  don't notice when I am using  12/3 verse 10/3 cord over a distance when using a high amp tool.

In 30 years I have always used 12/3 extension  cords and never noticed my tools doing anything weird or had a fire from a cord or anything like that.

I need to invest a few hundred dollars in cords, just wondering if I should go 10/3, this time. The 10/3 cords add about 30% to the cost if I shop well, up to 100% more if I don't look for sales.

 

[rizzoa13]

I make my cords out of Carolprene SOOW cordage now and I'd never go back. They are extremely light and flexible and carry large amperage for their size. With some neutrik ends on them they're amazing.

 

[Rip Van Winkle]

Most Manuals that come with the portable power tools I've purchased, have a chart towards the front that lists power cord gauge requirements, for different amperage levels, over different distances. For some reason the charts have never been customized for the individual tool the manual was for. The charts tend to vary a bit about how specific they are, but there is one thing that almost all the charts have been specific about.

To run a 15 amp power tool over a 100 foot extension cord, you should use a 10/3 gauge extension cord at the minimum.

I just checked the manual for my Porter Cable biscuit joiner. For a tool spec'd at 14-16 amps, 10 gauge was listed as recommended for a 100 foot cord. At 150 foot the cord recommendation went to 8 gauge. When you get to 200 and 250 feet, 6 gauge was recommended. For 300 and 400 foot cords 4 gauge was recommended, and for 500 foot cords 2 gauge was recommended.

Of the manuals I checked, Porter cable seems to have the charts that are larger and more specific. I checked an older Milwaukee drill manual, and Milwaukee seems to have less specifics, but was more conservative with extension cord recomendations. Milwaukees chart recommended 10 gauge at 75 feet for tools between 12.1 and 16 amps. For tools between 16.1 and 20 amps their chart stopped at 10 gauge over 50 feet.

Since the tools companies manufacture the tools, I presume they may have a better understanding of what kind of problems such as spike voltage, drop voltage, and duration of use could have on there tools, in regards to safety issues, and the performance and longevity of the tools.

I've never seen a regular extension cord bigger than 10/3. I presume if you want something bigger you wood have to look into purchasing wire and adding your own aftermarket plugs, or purchase heavier cords like the kind used for theatrical use, and purchase or make an adapter for regular 15 amp plugs.

If you wanted to go one gauge step below what is recommended, or slightly longer than what us recommended you probably would have an issue for sporadic use, since most tools don't operate at full amperage continuously.

In case you're wondering, after reading the charts I mostly only buy 10 gauge cords. I do have a couple lighter gauge cords for working at the top of ladders since I'm usually not using 15 amp tools in those situations, and the lighter cords are less of a hassle.

 

[Holmz]

I make my cords out of Carolprene SOOW cordage now and I'd never go back. They are extremely light and flexible and carry large amperage for their size. With some neutrik ends on them they're amazing.

They are good but no different for 12/3 other than maybe the OD is a bit smaller. The amps are the same.

Most Manuals that come with the portable power tools I've purchased, have a chart towards the front that lists power cord gauge requirements, for different amperage levels, over different distances. For some reason the charts have never been customized for the individual tool the manual was for. The charts tend to vary a bit about how specific they are, but there is one thing that almost all the charts have been specific about.

To run a 15 amp power tool over a 100 foot extension cord, you should use a 10/3 gauge extension cord at the minimum...
...

It is hard to argue with against a chart.

 

[mkasdin]

Also take into consideration where you're plugging the extension cord in. If it's 100 feet from the fuse box and you run an additional 100 feet of extension cord you are now 100 + 100 = 200 feet. That's the argument for getting thicker gauge. Along with the fact that I use larger tools like rotor hammers that require more amps? Also there's some resistance as you go further out so less amps?

So get the thicker stuff if you have expensive tools your running.  Or you could get a small generator like a Honda and then your set. Try it out on a small tool and see if the cord gets warm on the thinner gauge.

This was suppose to be a short reply. Go figure.

 

[Cheese]

I checked an older Milwaukee drill manual, and Milwaukee seems to have less specifics, but was more conservative with extension cord recomendations.

Referencing Milwaukee's more conservative ratings, I found this observation interesting. Attached below are pictures of two 12/3 rated extension cords, the Flexzilla is .435" diameter while the Milwaukee is .600" in diameter.

The Milwaukee is like using a small hose and coiling it up after use is a workout for the arms & shoulders.

The National Electrical Code specifies a 14/3 cord to be used for 15A service for 50'. Anything longer than 50' is downrated to 13A service. So a 100' cord used for 15A service should be a 12/3 cord set.

 

[JimD]

I googled up a table that says a 12 gauge is only enough for 50 ft if the load is 12-15 amps.  10 gauge in the same table is OK at 100 ft for the same load.  That may be conservative but helps to illustrate the difference.  The issue I worry the most about is the tool.  If you use too small a cord the voltage drop makes a universal motor draw more current which can cause it to overheat and fail.  I ruined an electric chain saw this way.

 

[AgentX86]

In general, a change of three AWG wire sizes doubles/halves the resistance of the wire, thus the length of an extension cord.

 

[Rip Van Winkle]

I've used smaller gauge extension cords in a pinch when that was what was available and I needed to get a job done.

I can also understand people objecting to the extra cost of a 10/3 extension cord, especially when you're talking about 100' extension cords that can cost more than $100.

Heavier gauge extension cords give you more "flexibility" though, on a job site.

Running a power tool off an extension cord off an extension cord that is undergauge can cause wear on the tool motor and underperformance of the tool. It can also cause high amperage tools to die a premature death. If you kill the armature of a decent saw you're out about the same cost as a 100' 10/3 extension cord, and that's just the parts cost. The cost is similar for a number of other power tools, especially higher end ones.

If you find yourself needing to run multiple power tools off a single extension cord, the heavier gauge cord will give you more flexibility to do so. A lower gauge extension cord will not give you the same flexibility.

If you need to run more than one extension cord for extra length, a heavier extension cord will also give you more flexibility, and less voltage drop over the extra long length.

A lower amperage tool will not care if you run a tool on a heavy gauge cord, but a high amperage tool may have an issue if you run the tool on a light gauge cord.

As far as weight, 100' 10/3 cords seem to weigh about 23lbs. This may seem heavy, but it's about the same weight as a plunge saw one you add extra blades and accessories.

They may exist, but I've never seen adapters that allow a person to use multiple extension cords on the same line to increase amperage capacity.

If you need more flexibilty near a tool, just keep some lighter capacity loer length cords to plug a tool into, and then plug the lighter cord into a heavief gauge cord for length.

 

[Rick Christopherson]

One of the things that rarely gets mentioned about extension cords is that the majority of the voltage drop actually occurs at the plugs, not within the length of the wire. So the last thing you want to do is use a bunch of short cords to make a long one.

Another thing that's a little interesting is that the resistivity of 12 and 10 gauge cords is not much different. 12 gauge cord is 1.5 ohms per 1000 feet (or 0.15/100), and 10 gauge cord is 1.0 ohms per 1000 feet (or 0.1/100). So for the voltage drop on a 100 foot (200 foot round trip) power cord with 15 amp load, you are looking at 3 volts versus 5 volts, due to the wire.

So the wire size isn't as big of an issue as the quality of the ends. Once you get into the 12 gauge cords, they usually have pretty good quality ends, and definitely do on 10 gauge cords. It's really the 14 gauge cords where you are going to run into significant problems right off the bat.

I wouldn't run a tablesaw off an extension cord, but for most hand-held power tools, it won't be super bad. Most hand tools use universal motors, which are more immune to voltage variations, because they will just drop the rpm's and output power unless you over-tax them.

Most Manuals that come with the portable power tools I've purchased, have a chart towards the front that lists power cord gauge requirements, for different amperage levels, over different distances. For some reason the charts have never been customized for the individual tool the manual was for. The charts tend to vary a bit about how specific they are, but there is one thing that almost all the charts have been specific about.

Actually, within limits, I do customize the tables in my manuals. I still keep the numbers very conservative, but I do tweak them beyond what most other manuals have. I could actually push the numbers even higher, but it is just easier not to.

 

[waho6o9]

We used a 100' cord with a spider box on it with great results, 12/3 is enough.
View attachment 1

"Is there a reason to spend the extra money on 10/3 cords of any length?"
I don't see why.

A skill saw is rated @ 15 amps or so and there wasn't a problem with said spider box, unless the
power pole was whacky.

 

[Tyler Ernsberger]

I have been buying all my cords from Home Depot.  The Ridgid cords have a life time warranty.  I go through cords quite a bit working on job sites and they always replace them if I have any issues.  I always buy 12 guage cords.  I have a 10 guage but only use it when running a compressor.

 

[Holmz]

...
... Most hand tools use universal motors, which are more immune to voltage variations, because they will just drop the rpm's and output power unless you over-tax them.

Most Manuals that come with the portable power tools I've purchased, have a chart towards the front that lists power cord gauge requirements, for different amperage levels, over different distances. For some reason the charts have never been customized for the individual tool the manual was for. The charts tend to vary a bit about how specific they are, but there is one thing that almost all the charts have been specific about.

Actually, within limits, I do customize the tables in my manuals. I still keep the numbers very conservative, but I do tweak them beyond what most other manuals have. I could actually push the numbers even higher, but it is just easier not to.

I take back what I wrote earlier about not arguing with a chart.
It sounds like you are applying some Kentucky windage to the answer.
The tool should have specs about what it needs.

I believe that universal motors are more about frequency than about voltage.

 

[Rick Christopherson]

I believe that universal motors are more about frequency than about voltage.

No, you have that backwards. They are called "universal" for the very reason that they are generally frequency independent, including being able to accept DC power.

 

[Holmz]

I should have said, "Universal refers more to being independent of frequency than independent of voltage".
So yes, we agree that they are independent of frequency.

The motor controller will be adding or removing voltage to maintain the target PRM up till it gets to the rail. It is probably more about loaded RPM than unloaded RPM.

 

[Rick Christopherson]

The motor controller will be adding or removing voltage to maintain the target PRM up till it gets to the rail. It is probably more about loaded RPM than unloaded RPM.

Sort of. With Pulse Width Modulation, the voltage is always line voltage, but it gets turned on and off rapidly to approximate a lower voltage on average.