Alright, electrical gurus, I need some help. As i posted on my other thread, I have my generator all set up. It has a 50A RV panel, and I used a 14-50P to 6-50R Welder Adapter Cord to get to something I can plug my welder into. Because the generator is standalone, I bonded my neutral and ground. I'm running an old school Tombstone welder...like an AC225 type.

However, when running, the welder barely gives me a usable arc. It's like it's running on half power. It's unusable. Measuring at the end of the adaptor between two hots and the ground, I get 115 on each leg. So, I am confused as to what the issue is.

Either the generator is not enough to run the welder, which seems wired since its 3 times the physical size of the largest Miller generator, or I have something wired not quite right in the box. Is this some bizarre instance where I don't need the neutral and ground bonded?

I don't know where to go now, since I thought this was a no brainer. LOL.

You say you have 115 between each leg and the ground. Do you have 230 across both legs? Do you have 60Hz?

Does the welder function properly on a regular AC outlet?

Todd 02 said:

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You say you have 115 between each leg and the ground. Do you have 230 across both legs? Do you have 60Hz?

Does the welder function properly on a regular AC outlet?

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YES....to all questions. Maybe this generator isn't as big as I think it is. Maybe I need to replace these capacitors. They test out ok but they are starting to seep a little. I'll do that first.

I KNOW this welder will run on a 5,000 watt generator when welding at 90A, so whatever this is sitting behind a 22HP diesel motor has to be big enough.

You don't need the neutral.

Is your gen set earth grounded?

Gator92 said:

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You don't need the neutral.

Is your gen set earth grounded?

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According to the pics in the other thread. It's a generator on a skid. There is no real earth ground.

Generator specs? Is the generator bogging down when you strike an arc?

Just checked out your other thread. Have you looked at what rpm you're supposed to run the generator at to give 60hz at a load?

WheelinAg said:

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Just checked out your other thread. Have you looked at what rpm you're supposed to run the generator at to give 60hz at a load?

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She doesn't bog down at all when I strike an arc. However, the voltage measured at the plug when striking an arc does drop to 200 and 190's.

The generator, based on my ear, is running 1800 RPM. There are only two options, 1800 and 3600, and 3600 on a diesel is screaming. This is purring along.

Frequency is at 61hz unloaded, which is normal for this machine.

Looked at your other post too but didn't see any info on the alternator. Is there a data plate, etc to give any clues what you are dealing with?

It may have less output than you think. Could need to be restrapped. Could be a speed control issue (large gensets have a speed control the makes the engine rev up to match demand). Could be a host of other things. Without knowing what your components are, they are all a guess at best.

Yes and unfortunately, that's the best I can do. The genset plate is long since unreadable and the company is now reduced to one old German guy that owned it and while helpful has made it clear that without the name plate, there is no means of knowing what the generator output is supposed to be as that model had innards that went from 6kw to 25kw…including three phase. He said we might be able to measure the housing but he's have to go through a room of binders from 30 years ago to maybe place it based on drawings.

It's not ideal. All I know is that I have 220v going into my welder.

I will say that I have accidentally hooked a power outlet up to this welder such that it was only running on 115v. This welder acts exactly like it did when I accidentally did that years ago. But this time I verified I have 220 at the outlet and while welding. And as I said the welder works fine on utility power.

I'm at a loss but again it doesn't make sense that a motor and generator so large it weighs nearly 1700 lbs would be too small to run a welder is beyond me. I dunno. Maybe just hosed. Kinda bummed out about it because I've needed a generator about once in 25 years so if I can't use this for welding, it's a 1700lb paperweight. Lol.

You mentioned caps. Where are they located? Between alternator and disconnect I assume?

Can you post a pic of how they are wired?

Is there any type of engine control or automatic voltage regulator installed on this setup?

Can you post detailed pics of the alternator, including wiring?

Did you wire it yourself or was it already wired and you just coupled it to the engine?

What's the input power rating of your welder? You mentioned running fine on 5000 watt generator. That's only 18ish amp of 240. Seems low for a welder but I've never owner that type of welder so I don't know what they typically run.

In my experience, running 60 - 500kVa gensets, voltage drop was almost always caused by overload. I suspect the same holds true for smaller gensets.

As a last ditch effort you may get someone to put a load bank on it and run it through increments to determine the load at which voltage drops below acceptable range. They may be reluctant w/o a rating plate on the alternator.

If you just want to run your welder off genset and don't care about this specific project, scrap it and buy a used genset. It will likely be cheaper and cause far less headache in the long run.

Caps are seen in the image below. Both are 25uF. They are both currently leaking, but still tested out ok. I am replacing those today.

Engine control is handled by locking the throttle to whatever speed is necessary to maintain 60hz and the appropriate voltage. That is done in the Lombardini 4 cylinder diesel motor.

I am not sure what you mean by 'alternator', but I'll get you whatever pics you want.

This unit is one you wire yourself. It came from my other house where the original owners left it. I do not know what it's original purpose was going to be or it's provenance but it is akin to something you'd use for a high output mobile work light as youd see overnight at construction sites.

I don't know the input rating on my welder. It's a Lincoln AC225 tombstone welder from the 70's. I have not run it on a 5000 watt generator, but I saw it done online on a youtube video for welding 1/8 rod on 90A setting. That is less than half it's capability and for it's duty cycle should not pull much power.

This is an older picture but the wiring in this end is the same and what I duplicated. From this it goes to a 50A RV power box like you'd plug your RV into. So, it's a box with a 50A breaker and a 20A breaker with a plug for 50A 220V service and 20A 110v service. I simply used an adapter to go from the 50A RV 4 prong plug to the one my welder uses. On the part where my welder plugs in, I directly measured voltage at that point and have 220v so It validates that it is wired up correctly for the hot side. There is 115 between the either hot and the ground/neutral prong.

I don't want to ditch this one, it's still big enough to use on the house and run some stuff, but I still have a tough time believing someone would strap a tiny 5k generator onto a 22HP 4 cylinder diesel motor. Seems overkill since you can get a 5kw generator on a 5hp chinese motor from harbor freight. So, that's why I was thinking somehting was amiss. The caps may be bad, but I fail to see how those could have an impact since I am getting the voltage I am supposed to have.


In the below image, ground and neutral is not bonded. In my setup, I bonded them at the panel I mounted. If I were using this on my house, I would unbond the panel on my generator since the house main is bonded.

I have a Lincoln ac225 as well and tried the same thing using a 4kw champion genny and had the same problem. Had to use the little 110 inverter welder to finish my pit out back. Sucks

I'm still trying to ID mine. Everything I see from the drawings and documentation say this is at LEAST at 16kw, if not a 22kw genny.

Is there any way to stress test a generator to determine what it's actual rating should be if you don't have tags? I replaced the capacitors. She won't strike a usable arc. the engine does respond when trying to, though. I can hear it.

The generator has a diode and two capacitors. That's all there is in the system that can 'fail'. These are all good. It's outputting 230v and 115v and that's that. I think I have to accept the fact that someone must have tied a 2,000 watt generator onto a 4 cylinder diesel engine because it doesnt produce enough power to strike an arc you can weld with. The previous owners had purchased this unit to power a 4800 square foot house, but based on what I see, they were going to be super disappointed. Guess I'll haul this POS back to barn and cut my losses.

This is probably one of my larger project fails. LOL. Thought this was a slam dunk...like buying an F350 to haul a jon boat..but nope. Been toting this thing around for 10 years hoping to be able to use it for something.

So I think this generator is actually less than 10,000 watts. It will run my tombstone on 3/32 6011 at 130A setting to get enough penetration. Once the weld is started, it will kind of run 1/8 rod if I bump the amperage to 130. It also runs my Lincoln Weldpak 155 MIG fairly well, not as well as on utility but enough. I was wondering if there is an inverter welder you guys recommended that I may be able to use instead. They use way less power.

Sorry I couldn't reply yesterday. Was at a conference followed by travel home.

Lots to unpack on this one.

The alternator is the part that generates electricity - connected to the engine.

You can't determine output capacity based on physical size. I've seen 3kVa gensets the size of a refrgerator laid on it's side.

You mentioned light tower. If that's where this alternator started life, it's likely less than 10kVa. Most light towers are around 6 kVa. All they are intended to run is the lights so they don't need large capacity.

I mentioned load test in a previous reply. If you can get someone to load test it, they can probably give you a good idea of capacity by watching for voltage drop beyond an acceptable level.

If you want to move to an inverter genset, I run a Miller Dynasty 250dx off a 3500 watt inverter genset...

Yeah, I don't think I will be able to get hooked up with that setup for less than 1000 bucks. I'll probably drop this 1800lb generator on a trailer and crank the tombstone up to 130A+ and SEND IT.

I really need to get a motor driven welder, but the idea of spending 2,000 bucks on someone's high-hour worn out piece of **** on Marketplace isn't OK with me. I've seen them where they look like they ran them over a truck after pulling them out of a lake with an asking price of 2000 bucks. Hard pass for me.

This generator will run any number of inverter welders, but without the ability to know the THD on it, it could kill the welder. The old transformer welder won't give a crap.

We tested everything on this generator and it's working fine. No shorts, everything checks out. It has run my 2HP well pump and a few fridges in the past, and that's about all I need it to do anyway, so it will be oK for that. Plus at 1800RPM diesel just coasting along, it will be good.

If you have access to an amp meter, hook your welder to utility power Burn some rods at full amperage and have someone take reading on one leg of the incoming power. That will tell us how much power you need to run the welder.

I don't think I can measure that with my Klein MM. Worried it will toast the leads. I think it's only good for 10A.

But, here is a stupid question...once we know this information, what good does it do me? If I don't know my generator output, and I can't change it anyway....

you can't do it with a typical multimeter. You need a meter with a pickup coil. Can be built in or some snap in as an accessory.

Knowing the amp draw at full load will tell you what size generator you need to run the welder properly. Then if you load test your genset you will know if your issue is load related or not.

Sounds like a damn fine excuse to buy a clamp style multimeter.

Tell me about load testing the genset. Who can do that? How do you do that? How does one test that without killing it? What does it in entail? Also, tell me about THD and how that can be determined from an unknown set. An inverter welder would be the bees knees here but apparently they are sensitive and need fancy generators that are less than 6%THD. Most I find are less than 12% which is fine for almost everything except this. Lol.

Alright, looks like burning 3/32 or 1/8 rods at 90a or 100a draws about 40A continuous while welding. However, setting my meter on "max" gives me a 58A Reading. This is presumably the spike required to get the arc started and then it settles down at 40A +/-

This means that if my math Is right, I need 9600 watts to run it and up to 14,000 and change to start it.

Based on what the generator company said … "it could be as small as 6400 watts or even 9000, but it doesn't physically look big enough to be a 15kw"….

Things are starting to align in understanding that the generator just isn't quite big enough. I still would like to know how big it is so I could get something to match it and work.

Since I'm welding drill stem pipe and it's about 1/8" thick, my wire welder will work ok. Lincoln says it's a transformer model so it won't care about power quality. It either works or it doesn't.