How much electrical power does a welder need?

[dourobob]

I am in the infancy stages of learning to weld and my friend has a fully equipped shop. So far so good. He has offered his experience and his shop to help me get started. After reading the many post from wroughtn_harv and many other experienced metal folks I think I need to fear getting pulled into the "now I need more powerful, bigger, stronger, etc." equipment and tools./w3tcompact/icons/laugh.gif Oh well, I am prepared to live with that. What I would really appreciate some advice on is the electrical power requirement to operate a welder. I've seen reference to 60 amp, 120 amp, 200 amp, 400 amp "Buzz Boxes" on TBN over the last while and it has confused my tiny brain./w3tcompact/icons/grin.gif

I have two possible locations for a "Welding Area" at home. One is the end of a Quonset barn that already has a separate 60 Amp service dedicated to the building. Is this enough to run a welder that would be capable of working with 1/4" and 3"8" steel for some tractor repairs, fabrication of some attachments (many ideas from TBN), etc.

My other option is a drive shed that has finally been cleaned out after 20+ years of accumulting stuff. That shed currently has a 12/3 line running from the house to power a couple of lights and a few hand tools like an angle grinder, circular saw, etc. As we are currently upgrading our entire electrical service for the farm I have a chance to do some preparation for running a service to this drive shed. A couple of folks have suggested running a 6/3 underground service (about 75 feet away) to a 60 amp sub panel in order to run a welder in this building.

Am I setting myself up for future frustrations 'cause I should have had more amperage or will there be enough electircal power in either of these location to operate a "Buzz Box"

BTW - my electrician is a great rural guy who has asked the inevitable "How much welding do you intend to do?" question. At thsi point I am thinking just as I described earlier but I want to be prepared for the the potentially addictive nature /w3tcompact/icons/grin.gif of this activity.

Any comments/advice would be appreciated. Thanks

Bob

 

[JonLeonard]

The power needed depends on the welder you buy. Mig welders require less power than a stick welder for example.

Here's an example
Miller Millermatic 135 (Mig) welder requires 20 Amps at 115 Volts
Miller Thunderbolt XL 300/200 AC/DC (Stick Welder) requires 67 Amps at 230 Volts

You dont want to load circuits more than about 80% (Sorry cant remember the exact number for the code), so you would need a 30 Amp 115 volt for the Mig and an 80 Amp 230 volt for the Stick. Thats a big difference.

The bigger the welder, the larger its power requirements and the higher its duty cycle generally. So its good to buy a welder rated higher than the maximum you will need. If you think you will need to use 140 amps to use a 5/32 6010 rod in a stick welder, look at a welder than can put out at least 200 amps to avoid long waits for the machine to cool down.

Hope this helps, but Im just a novice welder myself. Maybe one of the more experienced people can help even more.

 

[EdKing]

The Lincoln AC225 buzzbox, which you can get at Lowes for $220, requires 220v 50 amps. The input current will be lower as the voltage for welding will be lower than the input voltage, allowing a higher output current. This will do 1/4" and 3/8" fine. This unit is a lower end welder, larger welders with more features may need more input.Your 60 amp would run this as long as you don't run any other high draw items at the same time you are welding. If you plan on putting a sub panel in your drive shed, I would go with 100 amp service to allow for expansion, a larger weldor, plasma cutter, large compresser, etc. May as well get the extra service to start, rather than up grade later. When I build my garage, I plan on having a seperate 200 anp service for it, allowing me to get lots of neat "toys" without having to worry about power.

 

[Anonymous Poster]

Let me be very clear about this, the output current on a welder is NOT equal to the input current.
A machine like a Lincoln buzzbox, or Miller, running 1/8 rod will rarely have an input current over 30 amps. My P&H TIG machine, 400 amps out will only draw an input current of 100 amps.
There is a fantastic scam among people purporting to be electricians, one that has been going on for more years than I can recall, that involves bullsnotting people into oversized electrical services, because it is extra profit. This scam hasd also overflowed into the standby generator business.
Unless you have a specific item, such as a heat pump, or air conditioner, that has a huge inrush current draw, or electric heat, there is no need for a service over 100 amps in a house.
Most houses rarely draw more than 10 amps on either leg of the service.
Since nobody believes truth any more, I strongly suggest you buy yourself an inexpensive Amprobe type current meter, and read the results for yourself. They are all over Ebay for around $25-.

 

[dourobob]

Hi Franz
Thank you for that clarity. (Sincere not sarcastic /w3tcompact/icons/laugh.gif) I think you are saying the same thing as my electrician - unless I want to power up a whole shop full of tools a 60 amp service will do nicely and still leave me lots of room to have a few lights on so I can see what the heck I am doing /w3tcompact/icons/smile.gif
Bob

 

[gerard]

While I agree with Franz in principal I think the 10 amp average is a little conservative. My sump pump alone draws 8 amps and I thinka fridge also takes about the same. Granted, neithee one runs constantly but since you can't predict when things are going to come on/off I think most people opt to oversize a little. Ed King gave some good advice. I have an AC225, it's on a 50 amp circuit but I would never need that unless I needed the full 225amp output (which I haven't yet). I also have a 30 amp circuit that I've used the welder on using 1/8 inch rod without a problem.

 

[justractors]

I run my Lincoln 225 and Millermatic 250 both off the same 50 amp circuit breaker but not at the same time.
I do have a 200 amp service panel in the house but only because I run a 100 amp breaker from it to the shop feeding another 100 amp panel.
The shop also has a air compresser which is rated to draw 27 amps on a 30 amp breaker plus I also have a Miller plasma cutter which is supposed to draw up to 25 amps on a 30 amp circuit breaker.
I guess if I turned it all on it would blow the circuit breaker in the house, but then I only have two hands.

Bill

 

[JRP]

Bob,

Keep two things in mind:

1. The breaker exists to protects the wiring to the welder, not to protect the welder.

2. The welder will draw the namplate input amperage (for example 50 amps at 240 VAC) when providing the nameplate output amperage (say 225 amp). At less than full bore output, say 125 amps, the draw wqill be about proportional. For this example, about 25 amps.

You can run a big welder on a smaller circuit but risk tripping the breaker. I run my Miller 250X MIG, rated for a 50 amp input, on a 30 amp dryer outlet. The breaker has tripped once when I was welding 3/4" plate. I reset the breaker and turnded down the welder a bit.

If your electrical equipment is sound and properly installed the breaker will protect the wiring. However, if your electrical equipment is rigged or is in poor shape than taking a circuit to the limits has some increased risk of starting a fire.

For your situation, you probably can put a 50 amp breker for your welder in your 60 amp service and do just fine. The 12/3 circuit is too light.

Keep in mind that 8/3 SO cord is not real expensive and a 75' extension cord for your welder can be made up for about $100.


JR Poux

 

[EdKing]

Franz, Bob,
The reason I sugested 100 amp service is for the following senario. Say a few years down the road you decide to add a compressor, or a plasma cutter, then one day you and your friend Joe decide to build a big "hoomper-flazet". This way you can be welding pieces A and B while Joe is cutting/grinding/sandblasting etc. pieces C and D. I just like to have the extra capicity at the start, rather than have to upgrade. A 60 amp service will do just fine, as long as you don't try to run too many things at once.

 

[fractal]

I am in the process of installing a 50 amp plug so a friend can bring over his buzz box and show me how to weld. If I like it, I may buy one myself. I have a 150ft run of #6 wire from the main pannel in to the sub in the garage. I am going to mount a 50 amp plug a few ft away from the existing sub for the welder. It should work just fine as long as the electric dryer is not running when I weld.

The smallest sub I would put in any place I was going to run equipment is a 60 amp sub. I would probably run a 100 amp circuit to leave some capacity for a welder, an air compressor, ventilation and lighting. Why? Because the difference in price between #6 wire and #0 wire is much less than the cost to dig a new trench and burry bigger wire next year and far, FAR less than the frustration I would have with myself for not "doing it right" the first time. On the other hand, if you are not an "overkill" person, a 60 amp sub in the drive shed WILL run a basic stick welder (at least the 220a buz boxes that I have been considering) as well as some basic lighting and you will probably save 100 bucks on the wire. You just have to remember to turn off the air compressor before you start welding so it doesn't kick in while you are welding and trip the breaker back at the house.

Oh, and when you are digging that trench for the power ... make it oversize and run a separate conduit for telephone and computer cables so you can get on TBN while waiting for the buz box to cool down (20% duty cycle from what I have read) means you have lots of downtime between welds. Ask your electrician to make sure you get the data cables far enough away from the power cables to a) be legal and b) reduce noise.

 

[Anonymous Poster]

Ed, while it is always nice to have additional capacity on an electrical service, I certainly do with a 200amp 3 phase service to the shop, and 100 amps to the house, I'm standing by my original comment regarding a 60 amp service to a garage shop.
A couple years ago, when I got a new Amprobe with digital recording capability, I decided to play/learn with it before going out to a jobsite and looking like a fool. My house averages 3 amps on one leg of the service and fluctuated between 2 and 4 amps on the other side for a month. My initial thought was that I had something hooked up wrong, so I hung a pair of amprobes ahead of the current probes, and found the new digital was right on the money.
The biggest current consumers in any residential situation are split phase motors, such as sump pumps and furnace blowers, followed by well pumps and microwave ovens. After a lot of meter reading, I was able to learn most of the power in my house is consumed by those convenient little transformer supplys that serve such items as answering machines and such, along with a FAX machine. Those are the things that run up the total kilowatt hours.
Welders are an interesting load picture, but not huge current consumers. My Lincoln rotarys exibit a load spike as the arc is drawn, and then settle down to much lower current consumption. Transformer welders exibit the same current picture. The cooling fan in my P&H 400 amp TIG machine burns more current than is normally used in the actual welding.
The average garage shop welder is going to run at around 90 to 125 amps out most of the time, and an offhand calculation tells me that will rarely be more than a 20 amp draw on the input. Average shop compressors, nameplate horsepower 7.5 (realisticly 2hp) will usually draw less than 10 amps under normal running conditions, possibly spiking as much as 35 amps on startup. A 9" handheld grinder will rarely draw 10 amps, and a bench grinder is likely to run at less than 6 amps.
Initial startup spikes of inrush current shouldn't be a consideration in service sizing unless everything in the shop will be coming on at the same instant. This discussion isn't about peak shaving or load shedding, it's about a reasonable cost effective service size for a small home shop.
Nameplate amperage ratings while convenient rarely represent true amperage draw any more, since manufacturers have been overrating horsepower for sales. I learned a long time ago that amprobes are a lot more honest than nameplates.
While it is always nice to have a cushion when it comes to power, a cost/benefit analisys has to be done too. There is no point to overbuilding a service.

 

[Kodiak]

Ed:

I have a 1/2 finished hoomper-flazet sitting out behind the shop. Its only a medium sized one. I ran out of kajoodles to finish it, and haven't been able to find anymore in my neck of the woods. /w3tcompact/icons/laugh.gif

 

[EdKing]

Franz, I agree with what you are saying. In my situation however, it is not uncommon to have myself, my brother, and my wife's cousin all working at the same time. Right now I work out of a small shed out back of the house. It is fed by a 110v 20a circuit. When we are working on a project, we have to "take turns" operating different equiptment. When I finally get my garage built, I want us to be able run whatever we want at the same time without having to reset the breaker if we do it in the wrong combination. Will this cost more ? Yes, but to me it is worth the initial expense to have this convience. In the interim, I plan on running a 100a sub out to the shed so I can get the buzz box, and maybe some other stuff. Right now I am using a 110v MIG/wire weldor and going to another friends house to weld the larger stuff with his stick weldor. I find myself doing this often enough now that I have a tractor, that I want to get a stick weldor of my own.

That's why I sugested the 100a service. Its kind of like the saying about tractors, "You never here people complaining about having more horsepower than they need to do a job"

 

[EdKing]

<font color=blue>I ran out of kajoodles to finish it, and haven't been able to find anymore in my neck of the woods.</font color=blue>/w3tcompact/icons/laugh.gif

If you can find some rahootchadingys, cut off the whoyaas, and bend the defrabulators around, they should make a decent substitute for the kajoodles./w3tcompact/icons/wink.gif/w3tcompact/icons/laugh.gif

 

[Kodiak]

Great I've got a cantainer o them thangs stored right under yhe barrel of monkeys.

 

[wroughtn_harv]

Ya'll are just being silly. And probably making fun of my use of "whodunnits and incredible edibles". But that's okay. I understand. But I am taking notes........there might be a test later......../w3tcompact/icons/laugh.gif

The city inspector would probably have to hospitalized if he ever visited the shop. I've rented the place for ten years, I know, and I don't want to talk about it.

Sixty amp for the welder circuit. But piggy backed to the welder plug is a twenty five foot extension cord, eight three, with another welder plug on the end of it. That feeds power to the plasma, little mig, spa blower that feeds the sand blaster hood, and Little Giant power hammer.

Actually there's two extension cords piggy backed in behind the welder plug. The other is lighter for fifteen amp two twenty service to the high freq box for tigging and the punch press.

I can get away with this because I work by myself and I can usually only do two or three things at once.

 

[dourobob]

Thanks to all of you - just another confirmation of the wealth of shared knowledge and experience on this board. I am feeeling pretty fine about a 6/3 line with a 60 amp breaker for the shop - like wroughtn_harv I can only do two or three thingas at once but unlike him, I don't really know what I am doing yet /w3tcompact/icons/laugh.gif. My buddy who has volunteered to teach me has his work cut out for him.

Bob

 

[boustany]

Not wanting to enrich electricians unfairly, and being as I am in the process of getting power to my Qonset hut (major use: welder) I figured I would add my 2 cents.
Were I live (Ontario) it is completely legal and 100% kosher to do your own electrical work if you get a permit. The Electrical Safety Authourity inspects it and everything. So I have completely wired my house and am now working on the first of 2 outbuildings.
The cost of 'adding amperage' is relatively minor when you consider the total cost. True, cable is more expensive, but I spent CDN $300 running #3 (good for 100 AMP) to the garage, vs. the $200 #6 would have cost. The conduit, panel, etc., etc., and the trenching work (which I would have paid to do because I got to use my 3010 & backhoe) were all the same. So my little hut is set to 100 AMP, which is more than I will ever need.
My house is 200AMP, even though I could have got by with 100AMP. I think 100AMP is code minimum here anyway. Why didn't I run 200AMP to my hut? Because each strand of 200AMP cable is the size of a garden hose, and real brutal to work with.
Mind you, when I put electricity into the woodworking shop 200AMPs it will be, not that I'll like ever need it.
So, the electricians shouldn't charge that much more for more juice. If they do, look at DIY. Just get it inspected.

 

[Anonymous Poster]

DOUROBOB
HI IM A NEW MEMBER TO THIS WEB SIGHT AND I WES READING YOUR POST AND THOUGHT I WOULD CHIM IN
IM KIND OF A JACK-OF-ALL TRAIDS TYPE OF GUY (MASTER OF NONE) PUT KNOW A THING OR TWO ABOUT ELECTRICTY
YOUR 6/3 CABLE WOULD BE MORE THEN ENOUGHT TO RUN YOUR BUSS BOX.
HOW EVER THE THING THAT HASEN'T BEEN MENTION
IS THAT YOUR CURENT RATINGS ARE DIFERENT WHEN YOU GO UNDER GROUND VERSE ABOVE GROUND
EXSAMPLE #6 ALUMINUM WIRE ABOVE GROUND IS RATED
FOR 60AMPS @140 DEG F AND THE SAME WIRE BELOW GROUND IS ONLY 40AMPS
HOW EVER THE SAME SIZE COPPER WIRE WOULD BE 80 AMPS ABOVE & 55 BELOW
I WOULD RECOMEND (4)#2 COPPER RAN THROUGH A 2" PVC CONDUIT WOULD GIVE YOU ABOUT 95 AMP SERVICE AT THE BARN PROBLY BE MORE THEN YOU EVER NEED FOR A GOOD HOME SHOP AND YOU WOULDN'T HAVE TO LISTINE TO WIFE COMPLAIN THAT THE LIGHTS IN THE HOUSE ARE GOING DIM EVERY TIME YOU START WELDING.

WELDING TIP'S START OFF WITH 1/8" 6011 ROD BIT MESSY BUT GOOD STARTER ROD STAY AWAY FROM 6013 PAIN IN THE *@! TRY TO USE 7018 NICE ROD WHEN YOU GET THE HANG OF IT
WELL GOT TO GO
HOP THIS HELPS SOME