330A/BP - Shocking Me, Polarity Gremlins

[Kelvin]

Hey, guys,

I'm getting some weird behavior on my 330A/BP, serial number HJ210613. The machine seems to work fine, and it always has, but this summer I put a welding table outside my shop, and I was welding on it while leaning on it with sweaty clothes and was getting what felt like some minor shocks.

I put a voltmeter on the leads and my OCV is always 93VDC.

I also realized that somehow the polarity is flip-flopped. When I put the red voltmeter probe on the stinger and the black probe on the work clamp, with the welder set on "DC Reverse Polarity" (which I take to mean DC Electrode Positive), I get -93VDC. If I switch the welder to "Straight Polarity" (which I take to mean DC Electrode Negative) and keep the voltmeter probes in the same places, it shows +93VDC. This is backwards, isn't it?

If I put the red voltmeter probe in the stinger and stick the black probe 1/2" into the dirt next to my outdoor welding table (with the work clamp attached to my indoor table, which is on a dry concrete slab), I get a voltage of 45VDC between the stinger and the dirt.

No wonder I was getting shocked!

Can anyone give me any clues on what to look at to sort this all out? The electrical subpanel in the shop that feeds the welder comes from the main panel in the house, about 150' away, with a 100A breaker in the house feeding the subpanel in the shop. The receptacle into which I have the welder plugged in is fed by a 100A breaker (I also use this receptacle for my Sync 250) and the neutrals and grounds in the subpanel are attached to the same buss bar in the subpanel...there is no second ground rod out at the shop, as I was told this was a no-no.

Thanks for any clues. I have not checked to see whether I get the same behavior from my Sync 250, but I might...

[Kelvin]

Nobody?

[bevis28]

Im betting that if anyone knows, its duaneb55
You may want to try and contact him.

[MinnesotaDave]

Good chance the polarity flip is because the cables are connected to the wrong posts at the bottom of the machine.

Just switch them and it will be back to normal.

I get shocked when sweating sometimes too - just the way it is in my opinion - easy electrical path.

One time I was laying on the damp ground, welding with an AC buzz box, the stinger flipped over when I set it down and nailed me in the side - sucked.

[bevis28]

Good chance the polarity flip is because the cables are connected to the wrong posts at the bottom of the machine.

Just switch them and it will be back to normal.

I get shocked when sweating sometimes too - just the way it is in my opinion - easy electrical path.

One time I was laying on the damp ground, welding with an AC buzz box, the stinger flipped over when I set it down and nailed me in the side - sucked.

Ouch, thats gonna leave a mark.

[Louie1961]

I have read on here before that neutral and ground should not be bonded in a sub panel. Creates a hazardous situation. They should only be bonded at one point, where the service enters the main panel, or something to that effect. WillieB (Bill) or Brocolli1 (Ed) are a couple of the resident electricians who can shed more light on this. PM them if they don't respond

[Louie1961]

If you are reading voltage potential to the actual ground, I would be looking for a short somewhere as well.

[Kelvin]

OK, update:

1. Several of you were right on the polarity issue. The cables were attached to the wrong lugs. I don't know who hires the monkeys around here...

2. Still have something weird going on with a short or something making the stinger hot relative to the ground.

I made some measurements yesterday with the machine set on DCEN and got the following:

a. Work Clamp attached to Outdoor Table (which rests on four iron casters on concrete blocks on the ground): 88VDC between stinger and ground (dirt)

b. Work Clamp isolated on wooden sawhorse (but cable lying on ground): 55VDC between stinger and ground (dirt)

c. Work lead disconnected from welder at lug: 17VDC between stinger and ground (dirt)

Can anyone give me any clues on what to look at? Someone locally suggested driving a ground rod into the earth at the shop, and grounding the neutral + ground buss bar to that, as well as at the ground rod at the main panel at the house...

I wish I knew a way to test whether it's just "potential" between the stinger and the ground, or whether there's enough potential current that could actually hurt you. I mean, static electricity runs to thousands of volts, but it won't kill you if you're reasonably healthy, because there's not enough current to worry about...

[MinnesotaDave]

Note: mine is a separate main panel and yours is a sub-panel so I don't know if the following applies to you.

If there is no grounding rod attached to a main panel, it is wrong according to my power company.

When a power guy came out to locate a broken cable in the ground in the 90's, he checked my connections in the box for the shop.

When he saw no ground wire going outside he was very upset that I could end up dead that way (I did not install the panel and never checked for a grounding rod).

I immediately bought the grounding wire and rod he told me to get and installed them.

I'll still get a minor shock if I rest a bare sweaty arm on the table.

[Louie1961]

I am no electrician, and I only know a little bit about electronics from getting my ham radio license. But it seems to me the 330A/BP is a pretty simple circuit: It is a transformer, a bridge rectifier and some filters. if your output current shows potential to the actual ground/dirt, then I have to assume that the current is traveling back to the panel via your safety ground (since there should be no neutral connected to the welder) and then out from the panel to your ground rod. This would have to be an abnormal situation, most likely caused by a short somewhere inside the machine. You need to have the machine serviced to find the fault.

[Kelvin]

Thanks for the replies, fellas, please keep them coming.

Just for some more data points, I plugged my Syncrowave 250 (which I bought new in 2010) into the same circuit (after unplugging the 330A/BP to make room), put it on DCEP, plugged in the stick leads and:

1. With the work clamp attached to the indoor welding table, which is insulated from the concrete slab by hard rubber wheels: Voltage between stinger and ground (dirt) = 8V DC

2. With the work clamp lying on the (dry) concrete slab, about 7 feet from the doorway: Voltage between stinger and ground (dirt) measured about 2 feet from the slab (or 8 feet from the work clamp which was lying on the slab) = 50V DC

If the problem was entirely in the wiring of the 330A/BP, I would expect item #1 above (with the Sync 250) to show a voltage of zero.

Could the old transformer be inducing a current somehow, just as the primary induces current in the secondary...?

The problem is that I'm in the hinterlands, our LWS is about 60-70 miles away, and moving the 330A/BP to a tech for service is like moving a wrecking ball...

[MinnesotaDave]

Just looking at your original post, "machine works fine" and "shocked while leaning on the table with sweaty clothes."

I don't see the problem.

Was this tig or stick?

AC or DC?

[Kelvin]

Just looking at your original post, "machine works fine" and "shocked while leaning on the table with sweaty clothes."

I don't see the problem.

Was this tig or stick?

AC or DC?

DC stick. Actually, I needed to weld on the underside of the table, and the only way to do that was to lie down on the shelf underneath the table, which meant that my sweaty calf was touching the steel table frame, and if I touched the stick, zap...as was to be expected.

But then, I was doing something else, not even near the (grounded) outside table, and got what felt like a shock. So I started poking around with the voltmeter, and that's how I discovered voltage between the stinger and the earth...

[Louie1961]

1. With the work clamp attached to the indoor welding table, which is insulated from the concrete slab by hard rubber wheels: Voltage between stinger and ground (dirt) = 8V DC

Close enough to zero in my mind

2. With the work clamp lying on the (dry) concrete slab, about 7 feet from the doorway: Voltage between stinger and ground (dirt) measured about 2 feet from the slab (or 8 feet from the work clamp which was lying on the slab) = 50V DC

Kind of to be expected I think. Lookup a UFER ground. rebar encased in concrete makes an awesome ground. So I am not surprised if the concrete slab is conducting some current.

The one I would want to see on your syncrowave is with the work lead disconnected from welder at lug: what is the potential between stinger and ground (dirt)

As a side note, I will go test on my syncrowave, which has never shocked me to date