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Old 06-01-2013, 09:40 AM   #1 (permalink)
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Grounding HF Plasma Cutter??

I picked up a Harbor Freight Plasma Cutter 95136 yesterday, after reading lots of good reviews. The p. 6 of the manual says to connect a 14g wire from the green screw on the back to a workbench or other suitable ground. Why is this necessary? I can't tell that other similarly powered cutters (e.g Miller 675) have this requirement. Does connecting this screw to a workbench - the very same workbench that I'll be using a work table - and that sits on large plastic casters, actually do anything?

I'm no electrician, and I am confused, and need schoolin'.

Mark
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Old 06-01-2013, 09:43 AM   #2 (permalink)
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It's got a 3-prong cord, doesn't it? My Hypertherm just has the grounded cord and the ground clamp to your work.
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Old 06-01-2013, 09:50 AM   #3 (permalink)
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It does. That's why I'm confused. The manual says that it comes no plug, and that you have to install it yourself, but mine came from the (Chinese) factory with a molded 50a plug installed.

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Old 06-01-2013, 10:10 AM   #4 (permalink)
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The wiring diagram doesn't show a secondary ground (the screw on the back). I'd assume that the ground from the plug is wired to the frame. If you're concerned, I'd open up the case and check to see if the plug ground is actually wired to the frame. If it is, I wouldn't worry about it.
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Old 06-01-2013, 10:30 AM   #5 (permalink)
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If you're concerned, I'd open up the case and check to see if the plug ground is actually wired to the frame. If it is, I wouldn't worry about it.
Great idea. I did, and it is. The house ground comes in from the left, and you can see a component grounded to the case on the right.



The ground screw in the back (bottom corner, coming in from the rear of the case) doesn't connect to anything special:



Thanks man!

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Old 06-01-2013, 10:34 AM   #6 (permalink)
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Yeah, you're covered then. Adding anything to that ground screw isn't going to do anything for you. Possibly in other markets they sell it without a plug?
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Old 06-01-2013, 01:41 PM   #7 (permalink)
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With China built things who can really know.

Some places for what ever reason want every thing tied into the building ground .

It can make things real interesting
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Old 06-01-2013, 02:34 PM   #8 (permalink)
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Some appliances come with an external ground screw even though they have a a plug with a grounding terminal.A safety,covering all bases.......
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Old 06-03-2013, 01:30 AM   #9 (permalink)
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Page 6 of the manual?

Anybody else that would have just plugged it in and started using it?
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Old 06-03-2013, 02:05 PM   #10 (permalink)
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Page 6 says #14 wire minimum for ground.Actually should be a #12 considering the 19 amp draw.But the cord is likely 14 gauge... manufacturers are often allowed smaller sizes on cords.
I'm not familiar with these machines,does the work piece need to be grounded ?
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Old 06-03-2013, 02:12 PM   #11 (permalink)
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It does. There's nothing special about these machines, other than they sell them in a bunch of markets, and the manual claims you have to install your own plug. Mine came with a molded 50a plug installed, and I assume that's common for the US. As someone mentioned above, perhaps that ground screw is there for other markets. Still, is grounding to a "workbench", which may not be grounded, and is likely the same one the work piece is clamped to, all that great an idea?

I used it with just the cord ground, and everything worked fine.

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Old 06-03-2013, 07:51 PM   #12 (permalink)
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Quote:
Originally Posted by ScaldedDog:18708889
It does. There's nothing special about these machines, other than they sell them in a bunch of markets, and the manual claims you have to install your own plug. Mine came with a molded 50a plug installed, and I assume that's common for the US. As someone mentioned above, perhaps that ground screw is there for other markets. Still, is grounding to a "workbench", which may not be grounded, and is likely the same one the work piece is clamped to, all that great an idea?

I used it with just the cord ground, and everything worked fine.

Mark
How well does it work?
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Old 06-04-2013, 09:46 PM   #13 (permalink)
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How well does it work?
Pretty well, I think, though it's the first time I've really used one. Cuts 1/4" plate easily, though I did have a problem with the cut edges "welding themselves back together". I suspect that's my technique, though, not the machine.

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