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Thread: Longest reasonable 240V 24A extension cable

  1. #1
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    Longest reasonable 240V 24A extension cable

    I recently purchased a Hobart 210MVP to weld up some 1/4" steel plate in the yard. I intended to install a 220V outlet in the garage to facilitate the work, but the electrician said that would require a new underground conduit between the main panel at the house and the detached garage. Too much expense to do right now.

    I've used the welder in 120V mode with decent results (the work is decorative, not structural; complete penetration is not necessary), but I'd rather use 220V if I can.

    The nearest 220V outlet is a 220V 30A three-prong for the dryer at the main house, about 100 feet from where I need to use the welder. The welder uses a maximum of 240V 24A at its rated output. The owners manual claims that a 14 gauge extension cord may be used with a maximum length of 53 feet, but gives no other guidance. 14 gauge stranded wire has ~ 2.5 ohms resistance per 1000 feet, while 10 gauge has ~ 1.0 ohms resistance. Is there any reason I can't use 10 gauge to make an acceptable 100 foot 240V 24A extension cable that is safe?

    Also, any idea where I can get the appropriate plug ends?!? I think it's a 10-30 plug at the dryer and a 5-50 receptacle at the welder end.

    Thanks,

    Beuford

  2. #2
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    Re: Longest reasonable 240V 24A extension cable

    I think it will be OK from an amps perspective but you may experience a voltage drop at that distance. Someone smarter than I am will chime in and tell you I am sure. I saw one calculator that seemed to say if you were overall less than 125 feet wire length from the panel you would be OK with 10 gauge, otherwise any more and you would need 8 gauge.
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    Re: Longest reasonable 240V 24A extension cable

    I believe you're going to spend a good buck just on the extension wire alone. Did you think about a used generator??? After storm "Sandy" I picked up a nice generator to run my 220v stuff for $200. Now, I can throw it in the back of the truck and be totally mobile. I made an adapter to go from 3 prong(welder) to 4 prong (the generator) for about $25.
    Pete

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    Re: Longest reasonable 240V 24A extension cable

    Quote Originally Posted by Beuford View Post
    I recently purchased a Hobart 210MVP to weld up some 1/4" steel plate in the yard. I intended to install a 220V outlet in the garage to facilitate the work, but the electrician said that would require a new underground conduit between the main panel at the house and the detached garage. Too much expense to do right now.

    I've used the welder in 120V mode with decent results (the work is decorative, not structural; complete penetration is not necessary), but I'd rather use 220V if I can.

    The nearest 220V outlet is a 220V 30A three-prong for the dryer at the main house, about 100 feet from where I need to use the welder. The welder uses a maximum of 240V 24A at its rated output. The owners manual claims that a 14 gauge extension cord may be used with a maximum length of 53 feet, but gives no other guidance. 14 gauge stranded wire has ~ 2.5 ohms resistance per 1000 feet, while 10 gauge has ~ 1.0 ohms resistance. Is there any reason I can't use 10 gauge to make an acceptable 100 foot 240V 24A extension cable that is safe?

    Also, any idea where I can get the appropriate plug ends?!? I think it's a 10-30 plug at the dryer and a 5-50 receptacle at the welder end.

    Thanks,

    Beuford
    A 10 gage extention will work fine. I run my inverters off my generator all the time. Most of the time I try to stay to a 50ft cord but I have run 2 50ft cords several times when needed. Any good home improvement store will carry the cord and cord ends. If it were me I would go with 8/3 just because it would make the extention more versatile but 10/3 will carry the load ok.

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    Re: Longest reasonable 240V 24A extension cable

    8/3 SOOW cord at Home depot is right around $200 if you buy the 100 foot spool. So the expense is not bad. But I have 40 foot of that to connect my generator to my panel and it is heavy stuff to haul around.
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    Re: Longest reasonable 240V 24A extension cable

    I have a 100' 10/3 w/with ground, (SO) used for the same application in the shop and it's served me well for several years.
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    Re: Longest reasonable 240V 24A extension cable

    Quote Originally Posted by Beuford View Post
    I recently purchased a Hobart 210MVP to weld up some 1/4" steel plate in the yard. I intended to install a 220V outlet in the garage to facilitate the work, but the electrician said that would require a new underground conduit between the main panel at the house and the detached garage. Too much expense to do right now.

    I've used the welder in 120V mode with decent results (the work is decorative, not structural; complete penetration is not necessary), but I'd rather use 220V if I can.

    The nearest 220V outlet is a 220V 30A three-prong for the dryer at the main house, about 100 feet from where I need to use the welder. The welder uses a maximum of 240V 24A at its rated output. The owners manual claims that a 14 gauge extension cord may be used with a maximum length of 53 feet, but gives no other guidance. 14 gauge stranded wire has ~ 2.5 ohms resistance per 1000 feet, while 10 gauge has ~ 1.0 ohms resistance. Is there any reason I can't use 10 gauge to make an acceptable 100 foot 240V 24A extension cable that is safe?

    Also, any idea where I can get the appropriate plug ends?!? I think it's a 10-30 plug at the dryer and a 5-50 receptacle at the welder end.

    Thanks,

    Beuford
    .
    HF sells 10 ga extension cord which i just changed ends on 50 foot with coupon was about $60 plus cost of plug and outlet for 240 volt
    .
    they sell 100 foot extension cords too. you need 10 ga for 30 amp max
    .
    technically if you have volt meter reading 240 volts at the welding machine AND then you use welder at max settings you look at 240 voltage drop. if it drops below 220 volts i would use a 8 ga extension cord instead of 10 ga.
    .
    the longer the extension cord and the thinner the ga the more the voltage drops when pulling a lot of amps. this is why many electric motors have trouble starting with long extension cords as typically many electric motors pull 4 times rated amps on startup. a 12 amp motor trying to pull 48 amps starting up and the voltage at the end of a long extension cord can easily be reduced to below 90% of the voltage you would get at lower amp use.
    Last edited by WNY_TomB; 01-13-2016 at 12:04 PM.

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    Re: Longest reasonable 240V 24A extension cable

    Thank you all for your input. With the cost of the wire, a generator might be something to consider.

    Any thoughts on using it in 110V mode? I heard I could pre-heat the plate to ~ 400F and get reasonable results. The only load will be ~ 1ft of dirt behind the plate, and that won't be much of a load when it settles in. I figure 1/8" penetration in the steel plate would be more than adequate for the load.

    I could have done this with thinner plate, but the aesthetics of the 1/4" plate are better (or so says the wife...).

    Thanks again for all your responses.

    Beuford

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    Re: Longest reasonable 240V 24A extension cable

    I'd do it- it's just garden bed-correct?

    and start digging a trench.
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    Re: Longest reasonable 240V 24A extension cable

    you buy a expensive welding machine but cannot afford a heavy enough electrical extension cord for it ??
    .
    i have easily spent over $300 for welding cable extensions and $150 for a 240 volt extension cord is very cheap in comparison.

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    Re: Longest reasonable 240V 24A extension cable

    I'd use a 10 gauge extension cord. At distance you worry about voltage drop. The amount of drop depends on the amperage draw and distance. At 100' and 30 amps continuous you'd have 7.5 volts of loss. No big deal for most equipment. At 24 amps continuous it would be 6 volts drop. Still no worry. A welder, the loss is even less because the load isn't continuous. That's why the manual states 53' with a 14 gauge extension. The NEC allows for de-rating welder circuits based on duty cycle. Your machine has a 30% duty cycle at 150A. Looking at the table in section 630.11(A) you'll find the 30% factor to be 0.55, so 24 amps * 0.55 = 13.2 amps derated. Now if I use this adjusted amperage to calculate my loss it's only 3.3 volts.

    In reality you could use a 12 gauge extension and your loss would only be 5.2 volts but if I'm putting a 30 amp plug on an extension cord I normally don't derate the extension cord because who knows what the cord will be used for later. While 12 gauge would be fine for a welder... it wouldn't be suitable for a compressor for example.

    If your having the electrician run a conduit to the garage... I'd have him install a 100 amp sub panel in the garage so you can run more stuff. It starts with a welder and soon... you'll need a big compressor, lathe, iron worker, and etc.
    Last edited by forhire; 01-13-2016 at 05:17 PM.

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    Re: Longest reasonable 240V 24A extension cable

    A 10 gauge cord will put you right about 3% voltage drop at max, which is an old rule-of-thumb for acceptable drop. Takes 240 V down to 230 V, more or less.
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    Re: Longest reasonable 240V 24A extension cable

    Not counting the breaker ribbon, or fuse resistance, and connections, the wire alone a number #14AWG wire 100 feet long would give you a six volt drop in voltage. Or a 2.5 percent voltage drop at 15 amps. Number #14 AWG has as someone mentioned 2.524 ohms per thousand feet. At some expected amperage for that AWG wire probably 15 amps. If you increase the amperage up goes the ohms and voltage drop.

    The formula for voltage drop is ohms times amps. If you take say a 100 watt incandescent lightbulb, it draws .8333333 amps at 120 volts and has 144 running ohms. The ohms of the lightbulb when not lit are much lower. Once heated and lit the ohms go way up. The same is true of #14 wire. At 15 amps at 70 degrees Fahrenheit, it matches the ohms on the chart. But at 24 amps you may be way over the ohms stated in the chart.

    In the case of the lightbulb if we multiply .8333333 amps times 144 ohms we get a 120 volt, voltage drop witch is correct. If you put a meter to the hot terminal of a 120 volt lightbulb it will read about 120 volts to neutral. And of course the other terminal the neutral of the light bulb will read zero volts to neutral. Because there is a 120 volt drop across the lightbulbs 144 ohms.

    Many inverters are actually very efficient and they may very will function with a smaller chord, dangerously though, I would never connect more than 15 amps to a number 14 wire though.

    Sincerely,

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    Re: Longest reasonable 240V 24A extension cable

    300ft of 6awg (16mm˛) OFC is around $120 from Electron Beam. That will make a nice 100ft, 6/3 extension cord. Just saying Oh and the Female 6-50 receptacle is around $15 from HTP.
    Last edited by Oscar; 01-14-2016 at 12:18 AM.
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    Re: Longest reasonable 240V 24A extension cable

    well,
    there is a Jerry Rig that got me out of bind once. I needed close to 200 ft, and didnt have nearly enough of heavy extension cord. I set up what electricians call parallel feed. I made up a pigtale to connect 2 regular 12 awg cords, where white and black wires of each cord were running a phase, and grounds remained grounds. The pigtale had a 20 amp inline fuse spliced into each wire, so it was "almost " legal...
    cheers!

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    Re: Longest reasonable 240V 24A extension cable

    Quote Originally Posted by Tracksuitjunkie View Post
    well,
    there is a Jerry Rig that got me out of bind once. I needed close to 200 ft, and didnt have nearly enough of heavy extension cord. I set up what electricians call parallel feed. I made up a pigtale to connect 2 regular 12 awg cords, where white and black wires of each cord were running a phase, and grounds remained grounds. The pigtale had a 20 amp inline fuse spliced into each wire, so it was "almost " legal...
    cheers!
    There was a rule for that though. That two number #12 AWG wires can only carry the amperage of the next wire size up, #10 AWG. It may be because any difference in length causes the shorter wire to carry most or all of the load.

    Sincerely,

    William McCormick
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    Re: Longest reasonable 240V 24A extension cable

    Actually #14 wire 100 feet long at 15 amps gives you a voltage drop of 3.786 volts. And a 1.577 percent voltage drop at 240 volts. At 24 amps I can only guess what the voltage drop will be. Because the wire will heat beyond the 70 degrees the ohms are calculated on.

    If you have ever used a long #14 extension cord for a circular saw you know as it gets hotter it really limits the amperage to the saw.

    Sincerely,

    William McCormick
    If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.

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    Re: Longest reasonable 240V 24A extension cable

    Why not do a little more research and run a line to your garage yourself? If you can put plug ends on to make an extension cord you can put an outlet in your garage. Materials would probably be pretty close to the same as a 100' extension cord of 10/3 SO, even for a full 50A circuit.

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    Re: Longest reasonable 240V 24A extension cable

    Quote Originally Posted by Sharon Needles View Post
    Why not do a little more research and run a line to your garage yourself? If you can put plug ends on to make an extension cord you can put an outlet in your garage. Materials would probably be pretty close to the same as a 100' extension cord of 10/3 SO, even for a full 50A circuit.
    I agree with this pretty much. If you needed it NOW, you would have already called an electrician and cut your losses. Might as well do some research on your part, ask some specific questions here, and you should be able to get it done if your serious about it. Plenty of people here would be willing to help I'd say.
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    Re: Longest reasonable 240V 24A extension cable

    It's going to cost a wee bit more than a 100' 10/3 cord.

    Per code you can't just run a single 240v circuit to the detached geerage.

    Requires 4-wires to feed the detached building.

    Even if it was allowed you gotta dig a trench and if you go to all the work of digging a trench why in the world would you hamstring yer self with marginal 6g wire
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    Re: Longest reasonable 240V 24A extension cable

    If you look at the HD website they have 2ga 500 ft roll for under$ 150(http://www.homedepot.com/p/Southwire...2207/204786553) Then add up conduit (2inch) , sub-panel, and fittings to that for your cost rental for a trencher to dig with you could could then have the electrician to do the connection that will save you most of the cost. Some will work like this to save you money and them time. This will get you both 240 and 120 in your garge.

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    Re: Longest reasonable 240V 24A extension cable

    Yeah just run the line yourself, and save some money.

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    Re: Longest reasonable 240V 24A extension cable


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    Re: Longest reasonable 240V 24A extension cable

    Might be worth searching your local Craig's list for some used cords:
    https://chicago.craigslist.org/wcl/for/5678903455.html

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    Re: Longest reasonable 240V 24A extension cable

    Quote Originally Posted by -SWS View Post
    Might be worth searching your local Craig's list for some used cords:
    https://chicago.craigslist.org/wcl/for/5678903455.html
    Can look for cords for boats as well, usually all that's wrong with them is the terminals are arced out,almost all are 30 amps some up to 50

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