Trying to solve a setup that welds AC without a ground clamp
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  1. #1
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    Nov 2014
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    Trying to solve a setup that welds AC without a ground clamp

    So my local makerspace has an older Miller Syncrowave 180D. The other day while teaching some people how to weld aluminum I noticed that the ground clamp was not actually attached to the table, it was simply resting on top of the welder (welder is right up against the table but not touching. Ground clamp usually just grabs the corner of the table). This spooked me a bit.

    Our setup is as follows. Syncrowave plugged into 208V power on a normal cart. Ground for all lines on that subpanel and all conduit are connected to an earth ground installed very near the panel (less than 12ft). The welding table is all metal and is also attached to that earth ground. The earth grounds are all done with large (#2 or larger) ground cables.

    What scares me is the thought that it could have been grounding back through the ground terminal on the power plug. Caveat here, I am not electrically inclined. I can handle basic wiring, but advanced circuits are gibberish to me. I would assume however that there would be some isolation inside the welder to prevent something like that from happening. But I honestly do not know. I have not purposely tried to weld DC without the ground (though I swear i've forgotten it before on this table and it simply wouldn't weld).

    I'm hoping someone can identify why this is happening with AC and can tell me if there is something we need to correct. I would really like to make sure our setup is correct and safe.

  2. #2

    Re: Trying to solve a setup that welds AC without a ground clamp

    Yea welding power supply power can easily make it back through the ground on power tools. Smoked a number of them over the years. You are sitting there welding, and it just seems like the welder is not putting out enough power. Then you smell the hand tool power cord burning.

    Sincerely,

    William McCormick
    If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.

  3. #3
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    Re: Trying to solve a setup that welds AC without a ground clamp

    Define Makerspace ?
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  4. #4
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    Re: Trying to solve a setup that welds AC without a ground clamp

    Its not actually a ground clamp, it is the work clamp. Its not defined with positive or negative because it could have either polarity. A "ground clamp" is common usage but is incorrect. The welder is grounded through its power cable but the thing you are welding is not.

  5. #5
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    Nov 2014
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    Re: Trying to solve a setup that welds AC without a ground clamp

    Quote Originally Posted by TJS View Post
    Define Makerspace ?
    A makerspace is like a gym, except instead of having exercise equipment, we have all the tools you've ever wanted but can't fit at home. Welding shop with MIG, TIG, and a decent mix of fitup tools and certiflat tables, 4x8 CNC Plasma table, sandblast, grinders, saws, powdercoat, full machine shop with manual kneemill, engine lathe, drill presses, and a tormach CNC mill, fully decked out woodshop, auto area with lift and tools, a couple CNC laser cutters, various 3d printers, all kinds of electronics equipment, soldering stations, microscopes, various electronic components for projects, event rooms, classrooms, working areas/offices for rent. It's a fairly cool concept, and one that's catching on more and more. You sign up on a monthly basis and there are all kinds of classes offered to get you into whatever area you're looking to try out.


    Quote Originally Posted by Xsbank View Post
    Its not actually a ground clamp, it is the work clamp. Its not defined with positive or negative because it could have either polarity. A "ground clamp" is common usage but is incorrect. The welder is grounded through its power cable but the thing you are welding is not.
    yea yea yea. While that is technically correct I think we can all agree that if you say "ground clamp" everyone knows what you're referring to.

  6. #6
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    Re: Trying to solve a setup that welds AC without a ground clamp

    weld power will go down the line cord of the welder. travel through the ground system of the building and make its way back to your weld table through a ground connection. If you are lucky nothing burns up. Work clamp has to make connection the welder case through a chip in the paint. The HF will make it jump an air gap. Hold work clamp in the air and all you will get to the work piece is HF. Weld current will not happen.

  7. #7
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    Re: Trying to solve a setup that welds AC without a ground clamp

    "yea yea yea." It is true that everyone knows what you are talking about but its still wrong if you wish to discuss circuits. If you don't GARA about circuits, slap on the "ground" cable.

  8. #8
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    Jan 2015
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    Hamilton Ontario Canada
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    Re: Trying to solve a setup that welds AC without a ground clamp

    You ARE getting the Ground through the wires Grounding the table and welder. Why where I use to work never grounded the welding tables to the building or the service ground.
    Welders: IdealArc AC/DC 250
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  9. #9
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    Nov 2014
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    Re: Trying to solve a setup that welds AC without a ground clamp

    Quote Originally Posted by Xsbank View Post
    "yea yea yea." It is true that everyone knows what you are talking about but its still wrong if you wish to discuss circuits. If you don't GARA about circuits, slap on the "ground" cable.
    I responded the way I did because you jumped in solely to correct me on a technicality and offer no help on the subject.


    Quote Originally Posted by Ypop View Post
    You ARE getting the Ground through the wires Grounding the table and welder. Why where I use to work never grounded the welding tables to the building or the service ground.
    We grounded the tables so thoroughly because the manual for the welder instructs you to. At our last building we had issues with the HF messing with other things on the circuits, because we hadn't grounded everything correctly. So when we moved we followed the miller manual and grounded everything as they call out.

    I accept that my "ground" path, or circuit completion, is coming through the grounding scheme we have in place. Again, I would have assumed that the welder would isolate circuits such that the ground in the power plug would not connect through to the work clamp (happy now Xsbank?). If there should be isolation i will open up the machine and look for something wrong (I need to adjust the spark gap anyway). If the machine is simply not built this way I'll accept it and just emphasize to all our users the importance of not forgetting.

  10. #10
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    Re: Trying to solve a setup that welds AC without a ground clamp

    With High Frequency it superimposes the electrical circuit, in laymen's terms it can and will travel around the outside of the current carrying conductor.
    It makes for a great transmitter, many years ago we were experimenting with very high frequency units, I took on home one night to fool with it some more.
    It seems I crashed most of my Nabors TV signals (before cable/satellite)
    Not only can it send high frequency to your torch it can also travel down and out the circuit feeding it.
    All the major welding manufactures recommend EARTH grounding of GTAW equipment, and yes some codes do if fact require the work table to be EARTH grounded.
    That is to say a stand alone copper ground rod driven into the earth. You should never ground/bond your work table to your utility's ground.

  11. #11
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    Re: Trying to solve a setup that welds AC without a ground clamp

    Yes, as I stated in the original post, everything is connected to an earth ground. We drove a dedicated earth ground stake for this installation and to it connected the following per miller's instructions:
    - welding table
    - conduit for all circuits in the welding area
    - sub-panel grounds

    The main panel for the building is connected to it's own earth ground as well.

  12. #12
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    Re: Trying to solve a setup that welds AC without a ground clamp

    There is a change that your beaker panels ground terminal strip located within the panel is in fact bonded to the sheet metal of the beaker cabinet.
    This is code correct in many areas, as your welder could have back feed through the power sources sheet metal and then on through its ground to the panels bonded ground and in turn traveled through your conduit, etc to complete the circuit on your table.
    With out seeing your application it's anyone guess ,but the circuit would have to be completed somehow for the welder to work.

  13. #13
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    Oct 2015
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    Re: Trying to solve a setup that welds AC without a ground clamp

    The equipment ground is what goes back to the plug. That is bonded to the case of the welder. The transformer is isolated. I think you're getting an arc without the ground clamp because your table is grounded to earth. It can't, or shouldn't, get onto the equipment ground. That would be a ground fault and would indicate an internal failure of the equipment.

  14. #14
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    Re: Trying to solve a setup that welds AC without a ground clamp

    AC power to AC welder. The real source is the transformer at the pole with the nearest substation/power plant before that so on up the line. The welder is just another step up-step down transformer. Step down the voltage and step up the current. You've got your stinger through a rod to a piece on a well grounded table, that's the next best closed loop other than using the 'work lead'. Take the so called 'hot lead' from a wall socket & connect it to anything well grounded. It'll arc (weld). One leg of the power falls off the main line out there and hits the ground. It'll arc (weld).
    "The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt

  15. #15
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    Re: Trying to solve a setup that welds AC without a ground clamp

    It was isolated. Right up until the work clamp made contact with the grounded machine housing. Then the welding circuit and power circuit became intermingled.

    That alone would not have been noticed if it wasn't for the table also being grounded.
    My name's not Jim....

  16. #16
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    Re: Trying to solve a setup that welds AC without a ground clamp

    Quote Originally Posted by Boostinjdm View Post
    It was isolated. Right up until the work clamp made contact with the grounded machine housing. Then the welding circuit and power circuit became intermingled.

    That alone would not have been noticed if it wasn't for the table also being grounded.
    I think this might be what i'm looking for. I hadn't made the jump that the work clamp was touching the case, because the case is painted so normally this isn't possible. However, this particular miller has a lifting hook through the top of the case that is not painted. I normally go out of my way to keep the work clamp off it, but some members see it as a convenient place to clip the work clamp when coiling everything back up. I wonder if during the incident I describe it was resting against the lifting hook.

    I'll test out the theory tonight.

  17. #17
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    Trying to solve a setup that welds AC without a ground clamp

    Who grounds the work table?
    I always heard you were not supposed to ground it.

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  18. #18
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    Re: Trying to solve a setup that welds AC without a ground clamp

    Quote Originally Posted by yesindeed View Post
    Who grounds the work table?
    I always heard you were not supposed to ground it.

    Sent from my iPhone using Tapatalk
    I will repeat what I've said at least 3 times. The manual from Miller recommends doing it, so we did.

  19. #19
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    Re: Trying to solve a setup that welds AC without a ground clamp

    Quote Originally Posted by cegan09 View Post
    I will repeat what I've said at least 3 times. The manual from Miller recommends doing it, so we did.
    OK brother, i got it.
    Millermatic 211
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    Clausing 6339 Lathe (for sale)

  20. #20
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    Mar 2013
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    Re: Trying to solve a setup that welds AC without a ground clamp

    Look at the syncrowave manual again.
    It says that you should only ground the table IF required by electrical code. What is code? https://en.wikipedia.org/wiki/National_Electrical_Code

    But regardless of that, you could remove the ground clamp from the welder and bolt the "ground" to the welding table. Now the table is always connected to the machine.
    And the current always travels it's intended path.

    If you want the option to "ground" the workpiece as well you could bolt a short cable with a ground clamp to the table too.

    PS. HF on AC is used all the time. So you have a high frequency, high voltage current that will keep the arc going during AC. That high voltage current will jump any air gap just like a spark in a spark plug. That is why you have all the grounding recommendations. On DC the HF is just used to start the arc and then switched off.
    Last edited by Pete.S.; 12-06-2017 at 10:55 PM.

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