Good ground?

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AZ_guy
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Good ground?

Post by AZ_guy »

I’m in the process of setting up my shop Sabre sidekick and am having trouble getting to the numbers their saying. I was hoping I could run a single ground rod and be good to go because my house main panel tests great using the 100watt lightbulb test. 11 ground rods later I just keep creeping down, after 11 8 foot 5\8” ground rods I’m at 1.4 volts with the lightbulb test. Manual says I’m supposed to be under .75 volts.

How big a deal is it to get the down to that number in that lightbulb test, do I need to just keep driving rods till I get it. I’m almost out of space to drive them since they need to be at least 10’ apart, I can maybe drive 1 or 2 more with the space I have. Is it critical to get to that magic number, or did others just drive a rod or 2 and figure it was “good enough”?
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djreiswig
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Re: Good ground?

Post by djreiswig »

For what it's worth, I don't have any ground rods on my table and it works just fine. Not sure why everyone else is having problems.
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weldguy
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Re: Good ground?

Post by weldguy »

May not even matter if your using a standard air plasma. What plasma cutter will you be using on your ShopSabre?
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acourtjester
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Re: Good ground?

Post by acourtjester »

Have you talked to the local power or have an electrician check things out for you. Grounds can be hard to nail down, question is why is you mains great and away from them is not. You may look at the connections between the mains and where you have your table. In some locations when I was working we had to have a dedicated line run from the input mains to our equipment, no daisy chaining the ground along the way.
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Larry83301
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Re: Good ground?

Post by Larry83301 »

If my memory serves me, quality of ground rods depends on moisture content of the ground you are putting them into.


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robertspark
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Re: Good ground?

Post by robertspark »

Earth rods work like this... Drive the first one in and you get a reading

The second one you drive in will be 1/2 that first reading....drive in a 3rd and it will be 1/3rd of that first reading.... Drive in a 4th and it will be 1/4 of that first reading.....

You have ELEVEN earth rods driven in .... So your reading will be 1/11 of the first reading....

According to my rough calcs you would need ~ 21 rods to get below 0.75..... there is a bit of tolerance on these calcs so you may actually need a few more in practice.....

That is why sometimes an earth mat is used instead as it is about ground conductivity and contact area of the ground rod.... A mat offers a larger area.... Water table can affect these readings too....

If you MUST achieve a reading then yes you have to keep driving the rods in or install an earth mat.....

Do you HAVE to is really the question
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Re: Good ground?

Post by AZ_guy »

weldguy wrote: Wed Feb 26, 2020 11:37 am May not even matter if your using a standard air plasma. What plasma cutter will you be using on your ShopSabre?
I’m running a hypertherm 45xp.
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Re: Good ground?

Post by AZ_guy »

Is the ground more for the plasma cutter itself or the table. I ran this same hypertherm 45xp on my last table with a 4 foot piece of rebar as ground and it worked great and never had issues.
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Re: Good ground?

Post by robertspark »

This is a difficult one as grounds or earth's are locality based....

Here in the UK some supplies are provided with an earth or ground that should be sufficient (unless something changes.. ). Hence extra earth's are not normally required... If you add a generator that is different and you normally need another earth connection or mat

Really it depends on your supply....

Does your supply provide 3 wires or only 2.... ?

Note I can only speak for the locality where I am.... I'd suggest getting to know a local electrician and ask them in your locality

I use a pmx 45 non XP on. Domestic (house) electrical supply which is about 30 meters from the supply point of connection... I use my electric supply earth.

All earths are radial .... No loops between equipment....
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Re: Good ground?

Post by weldguy »

AZ_guy wrote: Wed Feb 26, 2020 2:47 pm
weldguy wrote: Wed Feb 26, 2020 11:37 am May not even matter if your using a standard air plasma. What plasma cutter will you be using on your ShopSabre?
I’m running a hypertherm 45xp.
Oh man I really doubt you need to worry about a ground rod with a 45xp. If it was high amp or high freq start machine then I could see it. I would just run it and I bet you will have no issues at all. I think if you were to call ShopSabre they would tell you the same thing since your using a 45xp.
AZ_guy
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Re: Good ground?

Post by AZ_guy »

weldguy wrote: Wed Feb 26, 2020 4:25 pm
AZ_guy wrote: Wed Feb 26, 2020 2:47 pm
weldguy wrote: Wed Feb 26, 2020 11:37 am May not even matter if your using a standard air plasma. What plasma cutter will you be using on your ShopSabre?
I’m running a hypertherm 45xp.
Oh man I really doubt you need to worry about a ground rod with a 45xp. If it was high amp or high freq start machine then I could see it. I would just run it and I bet you will have no issues at all. I think if you were to call ShopSabre they would tell you the same thing since your using a 45xp.
Ok thanks for the info. I’m just going to try run my system with the 11 ground rods I already have in lol. I ran this same plasma cutter before on my last time with a piece of 3 or 4 foot rebar in the ground for a ground and never has any issues with the cutter itself. If I start having weird issues I’ll look into it but I’m thinking I should be ok. Thanks again.
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Re: Good ground?

Post by weldguy »

AZ_guy wrote: Fri Feb 28, 2020 1:03 am Ok thanks for the info. I’m just going to try run my system with the 11 ground rods I already have in lol. I ran this same plasma cutter before on my last time with a piece of 3 or 4 foot rebar in the ground for a ground and never has any issues with the cutter itself. If I start having weird issues I’ll look into it but I’m thinking I should be ok. Thanks again.
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AZ_guy
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Re: Good ground?

Post by AZ_guy »

Just as a follow up I didn’t add any more ground rods. Been running the table a bunch over the last week and it’s working flawlessly. Thanks for the help guys.
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Re: Good ground?

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