Shocked by ground Lead on AC Stick Welder?

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Hello-I am new to this forum and need some help from experts on old AC stick Welders.  Currently have an old Forney model C-5 AC stick welder. Has the plug in sockets in front for the welding leads.  Was welding the other day, had machine on and touched work that ground clamp was attached to and got a shock.  Electrode holder was no where near the work and was sitting on a plastic trash can 5 feet from table that the work piece was on.  I then checked ground lead with a digital volt meter.  Hooked + on meter to ground clamp on welder, and - to ground on 120v outlet on wall and read 144VAC.  Any help as to what I should check would be appreciated.  Didn't think you should get shocked by the ground lead?  I understand you can get shocked if holding the two leads because you are completing the circuit, but the ground should have no voltage on it right? Welder  operates normal on all settings other than the ground lead being hot.  Positive lead plug taps have open circuit AC voltage of 70-40 VAC depending which tap you check.  This was measured with digital meter from electrode taps to ground taps on welder.  Thanks in advance!-Jesse
Reply:on 240 circuit center green wire suppose to be a ground wire not connected to a neutral even if they connect to same spot in electrical panel. a neutral being used elsewhere (other circuits) can have a voltage potential between it and a ground.they changed electrical code so that sub panels in a garage require 4 wires to main electrical panel. 2 hot, 1 neutral and 1 ground only used for grounding.,most 240 volt machines the outside frame of machine should be connected to ground only wire. if a hot wire is touching machine frame it should trip breaker. if machine frame is not grounded than if hot wire touches machine frame and you touch machine frame you would get potentially a 120 volt shock..your machine might have overheated enough the transformer insulation has burned off enough it is connected to machine frame electrically nowLast edited by WNY_TomB; 03-10-2016 at 11:31 AM.
Reply:Technically, what you are calling a 'ground' clamp is actually called a 'work' clamp. There is a reason for this. On some, if not all, tombstone type welders, and mag-amp style welders (Like the 330a/bp that I'm familiar with) there is no ground connection on the secondary side of the main power transformer. As such, a voltage difference could develop between ground and the work lead. The ground going to the machine connects to the machine chassis only.The ground to work electrical path should be a very high impedance path (IE:Not dangerous), unless there is some insulation degrading in the welder.Use gloves when working with your welder. This is the best control.Another way to correct this situation is to ground the table, but keep in mind if you lift up the piece from the table you are again ungrounded and may experience a poke.Chay
Reply:Hello-I should add that I have this welder hooked up to 208V single phase.  We have 3 phase power at the shop, and the transformer gives us 208, not 240V single phase.  Also, this welder uses the old style plug, 3 pin.  Red and black (hot wires) on the outside two pins, and white (common) on the middle plug.  When I test with digital meter from the hot taps on welder to a ground, I get around 200V.  When test between hot taps and ground lead taps get 43-70VAC (open circuit volts depending which tap was measured).  Tested to see if machine frame was hot. Got 0V when testing frame to ground wire.  I can touch frame and feel no tingling either.  When testing ground lead taps on welder to welder frame (+ on meter to ground taps and - on meter to frame), I got 145VAC on meter. Hope this helps.   Thanks so far!
Reply:Originally Posted by oldfarmallHello-I should add that I have this welder hooked up to 208V single phase.  We have 3 phase power at the shop, and the transformer gives us 208, not 240V single phase.  Also, this welder uses the old style plug, 3 pin.  Red and black (hot wires) on the outside two pins, and white (common) on the middle plug.  When I test with digital meter from the hot taps on welder to a ground, I get around 200V.  When test between hot taps and ground lead taps get 43-70VAC (open circuit volts depending which tap was measured).  Tested to see if machine frame was hot. Got 0V when testing frame to ground wire.  I can touch frame and feel no tingling either.  When testing ground lead taps on welder to welder frame (+ on meter to ground taps and - on meter to frame), I got 145VAC on meter. Hope this helps.   Thanks so far!
Reply:All transformers have a certain amount of capacitive coupling between the primary and secondary.  This may be worse in your case due to running the machine on three phase, as you're using two of the phases and are no longer balanced with respect to ground.  You might try a single phase 240v connection and see if that helps any.Another thing to check is to unplug the machine and open it up see if the transformer frame is grounded to the ground connection in the power plug.  With the machine unplugged, use your meter to measure resistance between the machine frame and ground pin on the power plug, and measure the resistance between the transformer frame (iron core) and the ground pin on the power plug.  Both should be very near zero ohms.You should also measure resistance between the power pins on the power plug (with it unplugged!) and the output connections (welding leads) on the machine.  Should be very high - essentially infinite.  Anything low indicates bad insulation on the transformer.Last edited by Thob; 03-10-2016 at 06:16 PM.Reason: Added additional resistance readings.Lincoln AC 225Miller Auto Arc 130 (Mig)Thermal Arc 186 AC/DC Inverter (Tig/Stick) - the "no excuses" machine
Reply:I have a c-5 stick welder.  I have never been shocked by it, but I have some questions about yours.  Have you ran regular 7018 on yours?  How good of shape is it in?  What is the year range of the model?  These are just things I have wanted to know (except the 7018).  7018 Runs smooth as butter on mine (AC), but never knew what luck others had.  Thanks!-JessForney C5 Arc WelderLincoln Idealarc 250-250 Ac/Dc Arc WelderMiller Bobcat 225g PlusLincoln PowerMig 200Forney O/A Rig
Reply:Three phase has 3 hot and 1 ground,Hots are red, black and white.Ground is green or bare copper.www.georgesplasmacuttershop.comPlasma Cutter and Welder Sales and Repairs--Ebay storeTec.Mo. Dealer Consumables for the PT and IPT torch's
Reply:Remember that electrical current always goes to a ground. I was welding on a dump truck years ago and I couldn't get at the right position. I put my ungloved hand on the damp concrete and started an arc with the electrode. I knew something wasn't right real fast as my hand on the ground was making electrical current go through me.  I would bet you were standing on a damp or wet floor or touching something that was making you a ground.
Reply:No, the normal for three phase is hot is black, red, and blue. If 3 phase wye, neutral is white, and ground is green. White should *never* be a hot, and if you use cable with white as a hot, it needs to be labelled with the correct color to so indicate.- Tim
Reply:The machines I'm familiar with will have the sheet metal of the welder connected to earth ground. The "ground lead" is a misnomer as it is one leg of a transformer secondary. On an AC machine this should be interchangeable with the stinger lead. If the work clamp arcs when it touches the welder case something is wrong.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:Two tests1  Put a 120 volt light bulb in the work clamp and touch it to ground (shouldn't light up)2  Take the work clamp and touch it to the metal case of the welder shouldn't spark (CAUTION, If it fails step 1, do not do step 2!)That meter will read a voltage between your two hands due to its sensitivity,
Reply:Originally Posted by drujininTwo tests1  Put a 120 volt light bulb in the work clamp and touch it to ground (shouldn't light up)2  Take the work clamp and touch it to the metal case of the welder shouldn't spark (CAUTION, If it fails step 1, do not do step 2!)That meter will read a voltage between your two hands due to its sensitivity,
Reply:Are you running 208 volts, or 120 volts from the 208 service?  A 208 volt service will have both hots 120v above neutral/ground . . . but if this was designed to run typical US 240V power, you would have the same thing . . . . Sounds like miswiring internally (is this voltage selectable?  If so, look really hard . . . ) or an internal fault . . . It sounds like one input leg is tied to chassis ground . . . again, if voltage convertable, perhaps someone "fixed" it to work on an ungrounded outlet . . . - Tim
Reply:Originally Posted by JessI have a c-5 stick welder.  I have never been shocked by it, but I have some questions about yours.  Have you ran regular 7018 on yours?  How good of shape is it in?  What is the year range of the model?  These are just things I have wanted to know (except the 7018).  7018 Runs smooth as butter on mine (AC), but never knew what luck others had.  Thanks!-Jess
Reply:Originally Posted by tadawsonAre you running 208 volts, or 120 volts from the 208 service?  A 208 volt service will have both hots 120v above neutral/ground . . . but if this was designed to run typical US 240V power, you would have the same thing . . . . Sounds like miswiring internally (is this voltage selectable?  If so, look really hard . . . ) or an internal fault . . . It sounds like one input leg is tied to chassis ground . . . again, if voltage convertable, perhaps someone "fixed" it to work on an ungrounded outlet . . . - Tim
Reply:There a transformer taps for the voltage internally . . . and wiring sounds correct, but somewhere, somethin has broken down . . . - Tim
Reply:Originally Posted by tadawsonThere a transformer taps for the voltage internally . . . and wiring sounds correct, but somewhere, somethin has broken down . . . - Tim
Reply:Originally Posted by oldfarmallChecked primary transformer.  I found the 208V power tap.  Switched wiring from 230v to 208V for primary transformer.  Still getting voltage on work/ground leads.  Called Forney, they think that somewhere in transformer something has broken down and is backfeeding from incoming power voltage back through work/ground leads inside the transformer.  Looks like I either get a different welder or use gloves when welding.  Welder welds fine though.
Reply:Originally Posted by tadawsonThere a transformer taps for the voltage internally . . . and wiring sounds correct, but somewhere, somethin has broken down . . . - Tim
Reply:Yes, capacitors can develop internal shorts.  My guess would be that it is for power factor correction.  If you get a new one, be sure to get a motor RUN cap, not a motor START cap.  Start caps are made for very short duty cycles, motor run caps are 100% duty cycle.  They are available on ebay or at a local motor repair or air conditioner repair shops.  Take the old one with you and they may be able to match the size so it mounts up easily.Lincoln AC 225Miller Auto Arc 130 (Mig)Thermal Arc 186 AC/DC Inverter (Tig/Stick) - the "no excuses" machine
Reply:Originally Posted by oldfarmall Forney says I can replace the cap with a 20uf 370VAC new one.
Reply:The capacitor may also be wired incorrectly. When you replace it, double check the wiring and make sure there is no connection between the capacitor and the secondary (welding current) side of the transformer.A few weldersA lot of hammersA whole lot of C-clamps
Reply:Originally Posted by ThobYes, capacitors can develop internal shorts.  My guess would be that it is for power factor correction.  If you get a new one, be sure to get a motor RUN cap, not a motor START cap.  Start caps are made for very short duty cycles, motor run caps are 100% duty cycle.  They are available on ebay or at a local motor repair or air conditioner repair shops.  Take the old one with you and they may be able to match the size so it mounts up easily.
Reply:Originally Posted by oldfarmallWell, I think I found the problem.  I started disconnecting things and testing with ohm meter this morning. There is a big oval capacitor inside the welder.  When I disconnect it I get no continuity between input power lines and the work/ground lead taps.  Hook it back up and I get continuity.  Haven't put power back to welder yet to see if there is voltage on the work lead taps yet.  Do capacitors get internal shorts?  What does this big cap do for this type of welder, and can I run the welder without it?  Forney says I can replace the cap with a 20uf 370VAC new one.  Thanks!Did a quick search (bored) . . . that cap should run you about $10 . . . Fastenal lists it at $6.06 wholesale if you deal with them, and a good electrical house may be cheaper yet.- Tim
Reply:Try to get a USA made capacitor, like the Amrad. The Chinese made ones are junk. Mexico run caps are decent, but still not as durable as the USA caps.Zach