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  1. #1
    Platinum Member dourobob's Avatar
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    Default How much electrical power does a welder need?

    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.[img]/w3tcompact/icons/laugh.gif[/img] 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.[img]/w3tcompact/icons/grin.gif[/img]

    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 [img]/w3tcompact/icons/grin.gif[/img] of this activity.

    Any comments/advice would be appreciated. Thanks

    Bob


  2. #2

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    Default Re: How much electrical power does a welder need?

    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.


  3. #3
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    Default Re: How much electrical power does a welder need?

    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.

  4. #4

    Default Re: How much electrical power does a welder need?

    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-.

  5. #5
    Platinum Member dourobob's Avatar
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    Default Re: How much electrical power does a welder need?

    Hi Franz
    Thank you for that clarity. (Sincere not sarcastic [img]/w3tcompact/icons/laugh.gif[/img]) 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 [img]/w3tcompact/icons/smile.gif[/img]
    Bob

  6. #6
    Veteran Member gerard's Avatar
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    Default Re: How much electrical power does a welder need?

    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.

  7. #7

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    Default Re: How much electrical power does a welder need?

    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

  8. #8
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    Default Re: How much electrical power does a welder need?

    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






  9. #9
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    Default Re: How much electrical power does a welder need?

    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.

  10. #10
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    Default Re: How much electrical power does a welder need?

    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.

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