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220 volt extension cord

Haven't used a store bought one, but have made a few (couple for a 60 amp arc welder, a couple for 30 amp 240v) just need plug, outlet, box, and suitable wiring (If using stranded copper, I'd tend to go a gauge or two bigger - smaller number - depending on what the "cord" was to be used for, and generally made them only as long as necessary for the purpose - too long and you have a greater voltage drop to deal with)
 
Paul Kuflik said:
Thank you! Do you think I need to go thicker than 12g for a ten foot run?
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12 gauge for a 10 foot run might be OK for a 15 amp circuit, just barely - if using stranded copper cable, I'd shoot for 8 AWG stranded for a 20 amp extension over 10 feet - that is assuming you are using a 20 amp outlet. 12 gauge solid core is the bare minimum spec for house wiring on a 20 amp circuit, and using stranded copper, you need to go a gauge bigger (10AWG) , and being over a 10 foot run, I'd tend to err on the side of caution and get 8 AWG (maybe overkill, but that's me)
 
Brian Gustin said:
12 gauge for a 10 foot run might be OK for a 15 amp circuit, just barely - if using stranded copper cable, I'd shoot for 8 AWG stranded for a 20 amp extension over 10 feet - that is assuming you are using a 20 amp outlet. 12 gauge solid core is the bare minimum spec for house wiring on a 20 amp circuit, and using stranded copper, you need to go a gauge bigger (10AWG) , and being over a 10 foot run, I'd tend to err on the side of caution and get 8 AWG (maybe overkill, but that's me)
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Where did you get that information?
 
I needed to go further for my lathe to get to the 220 outlet. Instead of an extension cord I just took out the OEM cord and made one the length I needed. Used a thicker gauge to account for the extra length. Was pretty easy to do.
 
The main reason for using a heavier gauge wire is to overcome any voltage drop over the distance of the length of the cord.
The lower the voltage the greater the voltage drop over the length of the conductor. You can calculate the voltage drop using
a formula based on the size and ampacity of the conductor and the voltage being utilized, or just plug the numbers into any
online voltage drop calculator. A 10 foot cord will have very little effect on your voltage at the end of the cord plug.

VD=IXR

Your voltage drop after 10 feet would be about 1/2 of 1 percent.
 
Rusty Nesmith said:
Where did you get that information?
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12 gauge bare minimum for 20 amps? National Electrical Code.

The rest of it? as I noted , JMHO - I tend to over-engineer things and go larger than absolutely necessary where it is feasible - The Stranded wire issue may be more common to DC circuits (automotive electrical) as stranded copper needs to be bigger to carry the same voltage/amps , so rule of thumb was if a circuit used solid core copper wire, you'd go up (or down, technically) one gauge larger , so a 18 Gauge solid core wire circuit being repaired with stranded wire should use a 16 gauge wire instead.

Shop I used to work at long ago, had mostly 14 gauge copper wiring (he was a DIY'er) and ran 20 amp breakers... One fine spring day when we were all busy in the shop running grinders (mower blades) chain sharpeners, and then a tech hooked in an electric impact wrench (new toy) to the same outlet that was running the grinder. 15 minutes the grinder started running weird and we saw smoke coming out the electric outlet.. Which was very scary, and after that I tend to go with the mindset that maybe a bit bigger will be just as good, nothing in the code dictates that you may NOT use 10 gauge wire when wiring a 20 amp circuit, as far as I know.. (just the budget since 10 Gauge is quite a bit more expensive)
 
Brian Gustin said:
12 gauge bare minimum for 20 amps? National Electrical Code.

The rest of it? as I noted , JMHO - I tend to over-engineer things and go larger than absolutely necessary where it is feasible - The Stranded wire issue may be more common to DC circuits (automotive electrical) as stranded copper needs to be bigger to carry the same voltage/amps , so rule of thumb was if a circuit used solid core copper wire, you'd go up (or down, technically) one gauge larger , so a 18 Gauge solid core wire circuit being repaired with stranded wire should use a 16 gauge wire instead.

Shop I used to work at long ago, had mostly 14 gauge copper wiring (he was a DIY'er) and ran 20 amp breakers... One fine spring day when we were all busy in the shop running grinders (mower blades) chain sharpeners, and then a tech hooked in an electric impact wrench (new toy) to the same outlet that was running the grinder. 15 minutes the grinder started running weird and we saw smoke coming out the electric outlet.. Which was very scary, and after that I tend to go with the mindset that maybe a bit bigger will be just as good, nothing in the code dictates that you may NOT use 10 gauge wire when wiring a 20 amp circuit, as far as I know.. (just the budget since 10 Gauge is quite a bit more expensive)
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True you can’t use 14 on a 20 amp circuit. 12 would have been fine. But to say a 10 foot cord of #12 would be good for a 15 amp circuit at best and to use 40 amp #8 wire for a 20 amp circuit isn’t even close.
 
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Paul Kuflik said:
Good question. It's a vicmarc 240 lathe that has not arrived yet. I'm trying to get ready.
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Okay, but the amperage rating really is the key to your answer. And, that said, if you are running on 240 volts your amperage draw will be less than at 120 v.
I can't imagine that changing out the entire cord of the tool would void the warranty. I recently did that on my Sawstop table saw.

Enjoy your new lathe, it looks like a nice machine!
 
The electrical department at your local big box store should be able to help you. I have made several that I take to some demonstrations. I like to be prepared for all possibilities.

robo hippy
 
Maybe you could add an extension (new) outlet (conduit & box) from your current outlet. Adjust wire gauge if necessary.
Last year I wanted to add a short extension for my 2hp DC. The cost of M&F plugs/receptacles and wire by the foot was jaw dropping (compared to when I originally wired my shop) !
 
You are right Tom. I went to HD this morning. Besides the fact that they were out of stock on so many items and wire choices, 15 ft. of 10g 3conductor was $65.00. That seemed quite high, though I can't say I have much basis for comparison. Plug were approximately $25 each.
 
Paul Kuflik said:
You are right Tom. I went to HD this morning. Besides the fact that they were out of stock on so many items and wire choices, 15 ft. of 10g 3conductor was $65.00. That seemed quite high, though I can't say I have much basis for comparison. Plug were approximately $25 each.
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Wow it is crazy where prices are going.
 
I'm not an electrician, but I think they consider the total length of the circuit when calculating wire gauge requirements. I would guess you're OK adding a few feet to a new cord of the same size and type.
 
Just for your information 15 Feet of copper wire with 10 amps running through it equals about 0.149 volt drop for 10 ga and 0.238 volt drop for12 ga or double for 20 amp. The worst case using 12 ga is still under 1/2 volt which will not affect the load/lathe and will not generate enough heat to be concerned about.
 
Don Wattenhofer said:
Just for your information 15 Feet of copper wire with 10 amps running through it equals about 0.149 volt drop for 10 ga and 0.238 volt drop for12 ga or double for 20 amp. The worst case using 12 ga is still under 1/2 volt which will not affect the load/lathe and will not generate enough heat to be concerned about.
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This obviously also assumes that the connections (plug and outlet) are (and remain) clean and tight. Should connections become corroded , screws loose (thermal cycling) , or in the case of stranded wires, "squished out" from under the screw heads from over-tightening (fewer strands connected essentially becomes a smaller gauge diameter wire) , among other potential pitfalls.. So, properly assembled plug and socket ends are also quite important for extension cords. (worn out electrical sockets that plugs fit loosely into, are frequent causes of electrical fires in homes... I've gotten burned fingers unplugging a vacuum cleaner at a friend's old house once before.. he got all his outlets replaced the next week.) Which is why I tended to err on the side of "beefier" when I made up purpose-built extension cords.
 
Brian Gustin said:
This obviously also assumes that the connections (plug and outlet) are (and remain) clean and tight. Should connections become corroded , screws loose (thermal cycling) , or in the case of stranded wires, "squished out" from under the screw heads from over-tightening (fewer strands connected essentially becomes a smaller gauge diameter wire) , among other potential pitfalls.. So, properly assembled plug and socket ends are also quite important for extension cords. (worn out electrical sockets that plugs fit loosely into, are frequent causes of electrical fires in homes... I've gotten burned fingers unplugging a vacuum cleaner at a friend's old house once before.. he got all his outlets replaced the next week.) Which is why I tended to err on the side of "beefier" when I made up purpose-built extension cords.
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All my 220v shop tools and outlets I've wired with twist locks. I've found you can count on them for cable strain relief as well as more substantial connections both inside the connector and between connections.
 
Brian Gustin said:
This obviously also assumes that the connections (plug and outlet) are (and remain) clean and tight. Should connections become corroded , screws loose (thermal cycling) , or in the case of stranded wires, "squished out" from under the screw heads from over-tightening (fewer strands connected essentially becomes a smaller gauge diameter wire) , among other potential pitfalls.. So, properly assembled plug and socket ends are also quite important for extension cords. (worn out electrical sockets that plugs fit loosely into, are frequent causes of electrical fires in homes... I've gotten burned fingers unplugging a vacuum cleaner at a friend's old house once before.. he got all his outlets replaced the next week.) Which is why I tended to err on the side of "beefier" when I made up purpose-built extension cords.
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Having to unplug a lathe to shut down the VFD would be more likely to wear out the plug and outlet or occasionally yank a strand or 2 loose. A shop environment might also have more debris, dust, etc. that can wear/reduce contact points.

When setting up my shop, I wired in a 2 pole switch for my lathe and drill press outlets.
 
Darryl Fective said:
Having to unplug a lathe to shut down the VFD would be more likely to wear out the plug and outlet or occasionally yank a strand or 2 loose. A shop environment might also have more debris, dust, etc. that can wear/reduce contact points.

When setting up my shop, I wired in a 2 pole switch for my lathe and drill press outlets.
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I have been unplugging my 3520 for almost 10 years, no wear on plug and wire is solid so no strand to come out if you tightened the strain relief screws.
 
Gerald Lawrence said:
I have been unplugging my 3520 for almost 10 years, no wear on plug and wire is solid so no strand to come out if you tightened the strain relief screws.
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I've also been unplugging my lathe since 1996 without a problem. I don't know (remember) what type of wire it is since I added the plug when I got the lathe 27 years ago.
 
Roger, your comment about running a 6.5 hp motor on a 20 amp circuit puzzles me. My Laguna 16HD bandsaw has a 4.5 hp Baldor motor on it and they specified a 30 amp circuit. Any idea why? Is it overkill? The electricians who installed the circuit seemed to think that 30 amps was proper.

robo hippy
 
robo hippy said:
Roger, your comment about running a 6.5 hp motor on a 20 amp circuit puzzles me. My Laguna 16HD bandsaw has a 4.5 hp Baldor motor on it and they specified a 30 amp circuit. Any idea why? Is it overkill? The electricians who installed the circuit seemed to think that 30 amps was proper.

robo hippy
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Probably should have said more or differently. The calculation is just what you get for 240 v X 20A = 4800 watts/746 watts/HP= 6.43 HP. So theoretical, just to make a point that the average lathe is no where near maxing out a 20A/240V circuit on #12 wire.

In the real world you shouldn't run circuits continuously at >80% of capacity and motor efficiencies aren't 100%, so yes, for a motor of 3 to 5 HP I'd run a 30A circuit on #10 wire. My 7.5 HP jointer/planer got #8. Plus, the manufacturer's specification supersedes any calculation or code requirement.
 
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