Generator to power welder

[fishman]

It's been a while since I posted. Rain makes Fishman busy!

I've got a problem. I've recently acquired a Hobart ac/dc stick welder and am having a lot of fun making stuff around my place. However, some of the more interesting projects I want to do are in areas with no power. For example, I'm currently building a combination boat/rv barn out of steel. My neighbor (God bless him) has been helping out with his Miller Bobcat. However, I would like to work on some of the smaller stuff when I have time. So my question is:

Can I run my welder with the 4000 watt generator I have? I think that is it's rated capacity. It is a Generac 4000 XL has a 7.8 hp engine. I have a pigtail to convert the 240 - 20amp plug to my welding plug so that part is o.k. However, the specs for the machine state 47.5 amps at 240 volts for it's rated capacity, which I believe is interpreted as maximum capacity. Given that I'm running it at much lower than max, can it be done? My generator has a breaker, so I can try it pretty risk-free, but I thought I'd ask here first.

Now, something a little more complex. If it can't be done with a single 4000 watt generator, can it be done with two hooked together? See, I have two of them, although one has been loaned to a friend. I don't have a clue how the wiring would look, or if it could be done safely. Anybody want to take a stab at that?

I try and make my questions challenging, at least

 

[reb]

I'm sure you are not going to find a way to hook up those two generators to one load. It would take some sophisticated synchronization circuitry.

Several years ago I had an identical generator, which I tried to use with a wire welder. After several tries to strike an arc, I gave up. Maybe it was my technique, but the generator would bog down whenever the arc started and the voltage dropped, killing the arc. I figured it would take a larger generator or one with a beefy flywheel.

 

[Soundguy]

As the other poster stated.. striking the arc is where the smaller generators run into problems. Otherwise your limit on amps output will be limite dby amps input.. EG.. you'll not be able to weld at full capacaty.. but rather at pro-rated capacity. based on input amps and input/output ratio.. etc.

Soundguy

 

[cp1969]

You could probably run a little 120V Mig welder off that generator but I doubt that even reducing the amperage of the stick welder will get you there. I was amazed when my generator wouldn't start my air compressor, which is well within the rated capacity of the generator. Not enough oomph.

If you look at the Miller Bobcat and Hobart gas welders, they have over 20 hp engines so that should give you an idea of what it takes to do stick welding.

 

[RonMar]

Power(P) equals Curent(I) times Voltage(E). 240volts X 47.5Amps = 11.4KW or VA. That generator is about 1/3 of what you need. Now you want to weld remotely on 4KW, try using it to charge batteries and do the welding with the DC current from the batteries.

 

[fishman]

So far it sounds like it's no joy in Fishman-ville. I'm going to give it a try with 1/8" 6011 and see what happens. Wish I could justify a pto generator

 

[Mickey_Fx]

As has been pointed out the figure originally give is 11.4kw and I question if this figure is correct. That would be one honking welder. What is the rated capacity of the welder? Typ stick welder one finds at home are in the range of 200-225A but that is secondry amps. These welders typ take about 5-6kW at their rated capacity.

 

[Highbeam]

It'll work fine on the low amp settings with smaller rods. Anyone who says it won't hasn't tried it.

I have tried it and done it again and again with my somewhat larger generator and similar AC225 stick welder.

You have the pigtail so give it a shot. Worst case, the breaker pops. No explosions.

The power equation Ronmar gave you is correct but the use of the equation is improper. The 47.5 amps of input power is at max load and worst case scenario to keep full welding output. What if you are only flexing the welder's muscle at say 1/3 of its max power. Hmmmm, less than 4000 watts.

Honestly though, your genset is pretty small for this so you will notice the difference. Striking the arc will take some more finesse and your limited power won't allow a good weld on thick material so do try it but don't settle for poor welds on a building just because they seem to stick.

 

[Soundguy]

I'd go for an easy strike type rod.. and as the other poster pointed out.. good metal prep.. and more passes with small rod.

To the poster witht he compressor not staring with a genny at rated specs.. well.. that's cause the motor start load can be 2x of the rated run load.. even more if it's an older unit.. etc.

Pto gensets are nice.. I've got a 12.5kw genny.. love it..

Soundguy

 

[fishman]

Mickey_Fx, I'm pretty sure the rating is 225 amps.

Highbeam: What would you consider thick material? I was thinking of welding 1/8"-3/16" thick clips to 1/8" purlin. Do you think it might be capable of 1/4" or is that "thick"?

Soundguy: An easy-strike rod. I guess you're talking about a 7014 maybe? 1/8" is what I have.

 

[Soundguy]

I'm actually talking about a brand name.. I buy some called ez-strike for my 'baby' 1/16 and 5/64 rod 70a welder... I'd swear that I could strike an arc on a piece of wet cardboard with them. Perhaps they make them in 1/8 as well.. or at least 3/32??

Soundguy

 

[fishman]

I wanted to provide the results of my experiment powering my AC/DC welder with a 4000 watt generator. It works!

I was able to weld 1/8" clips and weld plates/splices to c-purlin with no problem. I know it won't weld really thick stuff, but it did do fine with this. I even sectioned a couple of welds to make sure I was getting complete penetration. I was tickled pink!

Welded at up to 70 amps DC with no problem using 3/32" 6011. Also used some 1/8" 6011 but it did require a bit more amperage. I think I could have gone as high as 90 amps without bogging the generator down. At 70, it definitely had a load on it, but nothing serious. Certainly not as much as the load I usually put on it, electrofishing ponds for my lake management business.

As a result, the framework of my rv/boat barn is complete and ready for painting and sheet metal.

Thanks to everyone for all the feedback.

 

[Highbeam]

Good job! I love proving the naysayers wrong on this one. Even the Lincoln website claims you need some monster generator to power their welders. It may be so that they can sell more welder/generator combo units.

My new house has no 220v plug tied to the grid so all of my fix it jobs are done with the generator. Honestly I would rather weld on grid power due to silence and the lack of a surge when striking the arc on a genset but sometimes you just need the mobility.

Glad it worked for you.

 

[Soundguy]

No stove plug? Dryer outlet?

Soundguy

 

[Highbeam]

No stove plug? Dryer outlet?

Soundguy

Good point, I suppose those plugs are there but I would have to rig up an adapter and remove the appliances to gain access. Momma won't be happy.

 

[EddieWalker]

I'm a little late to this, but my experience is the same as Highbeam. I weld with smaller rod and a lower power setting on my generator and AC/DC arc welder from time to time.

Fishman,

How about starting a thread on your project?

Eddie

 

[fishman]

Yes it is great to find out something works against all odds.

Hi Eddie. I would love to start a thread on my project, but I just don't have time right now. I don't know how you do it on your end. You've provided so much detailed information on your projects and you do a LOT of them. I, for one, am appreciative.

I hope to post some details in a month or two when things slow down. I do have some pictures at least.

BTW, my welding/generator unit was able to output 90 amps without lugging too much the day before yesterday. It was a no-go with 1/8" 6011, but it welded great with 3/32.

 

[Soundguy]

Good point, I suppose those plugs are there but I would have to rig up an adapter and remove the appliances to gain access. Momma won't be happy.

My dryer sets 8" from the wall in the garage.. plenty o' room to unplug it and plug the welder in.. I just make sure I am not using more amperage than the outlet is rated for. That's pretty easy since I havn't had to weld at over the 120a setting yet.

Soundguy

 

[Highbeam]

I could and did weld all the way up the 225 amp setting on AC mode which takes less input power than DC mode but the arc wasn't as powerful as when using the grid power. Maybe the generator was putting out lower voltage. It sure would bark when I struck that arc.

We freeze too much to have our wash machines/dryers in the garage, I've always had them in the living space of our homes.

Just Friday I had to pull out the washer since I discovered by sound a dripping hose. Argh! The cabinets are built around the units so it is out of sight.

 

[Syncro]

I was about to start a thread on using my Lincoln 225 AC 'Tombstone' welder on a 4 KW generator when I saw this one already open. Kinda wish I'd have read all this good info before my own 'field trials', it would have saved me a lot of guess work. Coincidently, I have that same Generac 4000 watt generator and at first tried welding using 1/8" 6011 rod, man that was an absolute no-go as that sized rod at > 100 amps shut the generator right down. I had some stock gates that needed to be modified right away, so I went to Home Depot and rented a little 110v Lincoln wirefeed machine which worked fine on the generator, but marginally got the job done.

I still wanted to be able to use my stick welder for future jobs, so I started a little experimenting. First I bought some 1/16" rod and dialed the old AC Lincoln down to 40 amps. Presto! a nice arc and near perfect looking beads, but only good for really thin metal and those 1/16" rods burned up very fast. I figured the 'sweet spot' would be 3/32" so that was my next move, and it worked very well.

Bottom line for me was 3/32" 6013 rods at 75 amps for welding 1/8" stock. Actually pretty good looking welds and not overworking the generator, I was able to weld for prolonged periods of time. As others have stated, its a little tricky starting an arc using this small generator, but I found myself getting used that with practice, so its not a real problem. I like my stick welder, and this combination allows me to be mobile around the ranch, albeit somewhat limited on welding heavy stock.