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Old 11-16-2005, 12:08 AM   #1 (permalink)
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What size generator for mig welder

I have a 120v craftsman mig welder I'm trying to use and having a difficult time as you know if you read my last post. I rented a 3500 watt generator and tried to weld something but it didn't work out. When I would try to start the weld the wire would just fry and spatter. It doesn't spark and melt like it's suposed to. At least like I think it's suposed to anyway. Then a ball of slag built up in the liner and got the wire stuck so it wouldn't feed anymore. Before I start again and rent another generator, was the one I was using correct? Was it too much power or not enouph? The reason I have to use one is the frame I am welding is too far away from the closest outlet.
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Old 11-16-2005, 05:00 AM   #2 (permalink)
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How many amps does your welder draw? Multiply volts time amps and it should give a pretty close wattage. I.E. if your welder draws 30 amps X 120 volts = 3600 watts. The generator could be on the small side.
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Old 11-16-2005, 05:32 AM   #3 (permalink)
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Chances are the generator is on the low side. First, you cannot have "too much" power from a generator. Second, the 3500 watt is most likely peak power output. As Jeep says above, you're looking at about 30 amps max at that peak output.
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Old 11-16-2005, 06:15 AM   #4 (permalink)
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I would go with at least a 5Kw generator. I used that capacity generator to power up my old buzzbox when I had to do some fence repair last year.


Even with a peak output rating of 3600w, I would be suspect. As ratings for just about everything, they are most likely inflated to some degree.
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Old 11-16-2005, 01:49 PM   #5 (permalink)
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Blackdog,

Have you welded much? I don't mean to be a smart alec but was just wondering. As others have said, your generator is a bit on the low side but I have done it before. Having said that you need to go with really low amps and feed rate and be prepared that the weld may not be a pretty sight.

Have you gotten familiar with your welder when it is plugged into a wall outlet? You mention slag, I just wanted to make certain that it is working properly. "Slag" buildup could be caused by the gas not flowing properly, perhaps not enough voltage to kick the solenoid. Possibly try skipping the shielding gas and use flux cored wire.

How far away is your outlet? I'd suggest making up a temporary extension cord out of romex or any heavy wire you have laying around. It will work a lot better.

Good luck!
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Old 11-16-2005, 02:40 PM   #6 (permalink)
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that little welder is only pulling 15-20 amps. Most 110V welders can run off a 20 Amp circuit. So at most 2400 watts continuous.
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Old 11-16-2005, 04:31 PM   #7 (permalink)
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i second the extension cord and the use of flux core over gas. any breeze at all will blow away the shielding gas causing the splatter you are describing.
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Old 11-16-2005, 04:52 PM   #8 (permalink)
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I used my old Lincoln (mid 1980's mfg.) to power a Millermatic135 a while ago. It worked fine for the garage door I was fixing, no problems whatsoever. Don't think I'd want to weld a frame with that small of a mig. Only thing I did to the Lincoln was switch it to high idle instead of automatic. I think your mig would have about the same power requirements. Pics tell a thousand words.....




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Old 11-16-2005, 08:02 PM   #9 (permalink)
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I have used my Lincoln WeldPak 100 (120 volt wire feed) several times with my 2250 watt generator (18.75 amps). It worked fine. I think a 3500 should power any 120 volt wire welder ?
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Old 11-16-2005, 08:48 PM   #10 (permalink)
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Nope, haven't welded much at all. I am obviously way over my head. I don't really know what I'm doing, I borrowed this welder from a friend, and I'm probably going to end up taking it to someone to finish it up. I haven't been using gas at all, and as for wire I only have one kind in there. It's just thin copper wire. I don't think the tip on there will allow for anything wider.

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Blackdog,

Have you welded much? I don't mean to be a smart alec but was just wondering. As others have said, your generator is a bit on the low side but I have done it before. Having said that you need to go with really low amps and feed rate and be prepared that the weld may not be a pretty sight.

Have you gotten familiar with your welder when it is plugged into a wall outlet? You mention slag, I just wanted to make certain that it is working properly. "Slag" buildup could be caused by the gas not flowing properly, perhaps not enough voltage to kick the solenoid. Possibly try skipping the shielding gas and use flux cored wire.

How far away is your outlet? I'd suggest making up a temporary extension cord out of romex or any heavy wire you have laying around. It will work a lot better.

Good luck!
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Old 11-17-2005, 12:40 AM   #11 (permalink)
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If you (or anyone for that matter) makes an extension cord out of romex be careful with it. My construction wiring teacher in college told me about a guy that he knew that made one and had it running across his yard for far too long. Apparently, the coating on romex is not designed to hold up to UV rays and the outer sheathing and the coating on the wires broke down. The guys little boy ran outside and stepped on a bare spot and was killed. Please be careful.
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Old 11-17-2005, 04:49 AM   #12 (permalink)
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We are working on a project now using similar mig setups powered by 5500 kw Multiquip generators with no problem. We did have problems with one of our older/weaker generators so we swapped it out for a newer one.
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Old 11-17-2005, 05:41 AM   #13 (permalink)
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Quote:
Originally Posted by Blackdog76
Nope, haven't welded much at all. I am obviously way over my head. I don't really know what I'm doing, I borrowed this welder from a friend, and I'm probably going to end up taking it to someone to finish it up. I haven't been using gas at all, and as for wire I only have one kind in there. It's just thin copper wire. I don't think the tip on there will allow for anything wider.
The "copper" wire is actually steel with a copper coating to keep it from rusting. If you are not using flux core, that would be the sum total of your problem. Unless it is flux core, you need to run a shielding gas.
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Old 11-17-2005, 08:54 AM   #14 (permalink)
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Blackdog,

Everyone has to start somewhere, and that's what you're doing now so I'd say don't give up! You may be in "over your head" as you say but that is how life goes on, and what you make of your life depends on how you deal with stuff like this. So don't abandon ship just yet

As with anybody, sometime think about taking a welding class at a community college, it will keep benefitting you for a long time if you choose to keep playing with metal things that will eventually break.

In the meantime, this is what I'd suggest- look up the operators manual online and read it, it will tell you how to do basic welding. Buy a roll of flux cored wire, the smaller diameter the better, and plug the welder in somewhere and practice laying some beads down. Then do teh other stuff that has been discussed.

I have faith you can do basic welding here!

Josh83- Sorry but I'm calling BS on the shop teachers story. If you step on a bare wire or wires the current will flow between the two conductors, so you might have a burned foot (and a pissed off mom!) but it really cannot electrocute anyone.

I do agree one shouldn't leave romex laying out, but any extenstion cords need to be thought of as temporary and leaving them laying around outside is bad form anyway. They are aways a nice trick to have up your sleeve though.
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Old 11-17-2005, 09:38 AM   #15 (permalink)
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Actually, the issue with Romex is more that it is solid wire and therefore will fatigue and break over time if rolled up, unrolled, kinked, etc. I've used it temporarily when I felt I had to, but was careful of it. Along those lines, don't use "used" Romex to wire a building. An acquaintance did that - pulled the wire out of a building that was being demoed and used it to wire his shop. Burned the place down in an electrical fire. Fire marshal figured that it was an internally shorted wire.
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Old 11-17-2005, 11:32 AM   #16 (permalink)
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Quote:
Originally Posted by PAToyota
Actually, the issue with Romex is more that it is solid wire and therefore will fatigue and break over time if rolled up, unrolled, kinked, etc. I've used it temporarily when I felt I had to, but was careful of it. Along those lines, don't use "used" Romex to wire a building. An acquaintance did that - pulled the wire out of a building that was being demoed and used it to wire his shop. Burned the place down in an electrical fire. Fire marshal figured that it was an internally shorted wire.

That is an excellent post PAT.


My father is a Master Electrician and owns his own shop. Everytime someone asks him to install "used" hardward, he just grins....Hell, he has a hard time using old breakers, especilly of PE or Zensco style, to provide temp. power for his customer while he tracks down a new breaker.



When I was young, I used 16ga solid wire to provide power to a lot of accessories on an old Ford truck I used to own. Over a period of months, all but one accessory lost power....solid wire cannot handle vibration/fatigue.
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Old 11-17-2005, 12:47 PM   #17 (permalink)
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I've had some excellent teachers through the years. Electrical work is not rocket science, but you definitely have to understand the rules to know why not to break them and also to know when you can get away with breaking them - hopefully temporarily.

Actually, that applies to a lot of things. I always hate when someone says "don't do" something but doesn't explain why. Is that just because you've always done it a different way? Or is it really an issue of life and death? I've always liked to know the difference so that I can make my own conclusions.

"Don't use Romex as an extension cord" in itself does not give you enough information. Somebody is going to figure that because it is good enough in their wall, it should be good enough as an extension cord and the other guy is just blowing smoke. "Don't use Romex as an extension cord because you'll get wire fatigue, a short, and a possible fire" lets you know the possible outcome. Then if you have an emergency situation and only have Romex, you can use it but know what to keep an eye on.

Also helps when you go to buy wire for something and the guy asks you if you want solid or stranded wire - you know why you'd want to use one over the other.
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Old 11-17-2005, 07:46 PM   #18 (permalink)
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We'll just wait till he replies....
Great info everyone!
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Old 11-18-2005, 07:16 PM   #19 (permalink)
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The extension cord talk has me thinking whether you plugged the welder directly into the generator or ran an extension cord from the generator to the welder.

Even a small welder takes up most of a circuit's current upwards of 14-15A, and a small 16AWG extension cord just adds to the resistance. Case in point, I tried running my pressure washer thru an extension cord to get it out to the end of the driveway.. It just hawwed and buzzed and never built up any pressure to the nozzle. Plugged directly into the wall it runs perfectly.
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Old 11-18-2005, 10:39 PM   #20 (permalink)
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Nope, that was the point of the generator. I backed up my truck to the project I was welding and plugged it in. I never even had to unload it from my truck when I rented it from Hertz.

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The extension cord talk has me thinking whether you plugged the welder directly into the generator or ran an extension cord from the generator to the welder.

Even a small welder takes up most of a circuit's current upwards of 14-15A, and a small 16AWG extension cord just adds to the resistance. Case in point, I tried running my pressure washer thru an extension cord to get it out to the end of the driveway.. It just hawwed and buzzed and never built up any pressure to the nozzle. Plugged directly into the wall it runs perfectly.
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Old 11-19-2005, 06:07 AM   #21 (permalink)
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Blackdog76, it appears you are using straight steel wire intended to be used with shielding gas. If this is so, you'll have all kinds of problems trying to run a bead. Generally, if your welding out in the open (subject to wind), you use flux-core wire and no gas. Two suggestions: Get a book such as Welder's Handbook, by Richard Finch. Second, practice indoors on scrap before attempting a real project.
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