Ground the welding table?

[Grumple]

I am guessing this will be like a "best oil" thread on a motorcycle forum, but I need to get this right. My Syncrowave 250DX has worked fine on DC every time I used it and now I have a problem after using AC to weld aluminum. Long story short, expensive PC1 card. Anyhow, while I wait till the new card shows up, I learned that tying the first 2-3 feet of the welding cables together can reduce RF so I will do that even though I don't know of any issues I have had yet. I read a little about grounding the all steel welding table too and there seems to be differing thoughts on this. My question: Should I ground my welding table? If yes, should I drive a new ground rod in as close as possible to isolate this ground? Should I use stranded or solid conductor to connect it?
My welder is backed up to a wall in a steel building and its easy to install the rod as I already bought it. I have the main service entrance panel approximately 20 feet away on the same wall and the main building ground rod is there. I also have another isolated ground rod for a powder coat oven on the back wall of the building. Would driving another ground rod(isolated) within 20 feet of the main service entrance ground rod create any problem? Like a ground loop or some weird thing?
Thanks,
Grumple

[cruizer]

Problem with ground rods is " Where is concrete rebar", cause that weld/hf signal will then literally go everywhere. And soil conditions, cause if its wet, that weld HF signal will go to your neighbors computer, tv and alarms, ect...

Ground rods are pointless to say the least. Maybe leave them for your occasional lightning strikes.


Now directly bolting a ground (work) to your table is ok. However, if your thinking of also installing a 110 receptacle, don't. Also don't push your table up to say a conduit or metal wall. Really want that table completely isolated from its suroundings.

[mbramble]

Sorry for hijacking!! But, Cruizer -- since you mention you should not mount a receptacle to the table.......

I just built a cart for my Multimatic 200 and was thinking of mounting a box with 2 duplex receptacles, and a short male plug pigtail out of the box. That would allow me to plug the pigtail into an extension cord and provide me some 110V outlets for grinders, etc. 4 outlets would just be a convenience so I don't have to plug/unplug power tools. Only one would be used at a time. And, this outlet would have nothing to do with the power to my welder (other than it comes from the same house electrical wiring system) - it gets power from a dedicated 220V outlet. Will I have any type of problems with this arrangement??

Thanks -- and back to the OP's problem!!

[Grumple]

Problem with ground rods is " Where is concrete rebar", cause that weld/hf signal will then literally go everywhere. And soil conditions, cause if its wet, that weld HF signal will go to your neighbors computer, tv and alarms, ect...

Ground rods are pointless to say the least. Maybe leave them for your occasional lightning strikes.


Now directly bolting a ground (work) to your table is ok. However, if your thinking of also installing a 110 receptacle, don't. Also don't push your table up to say a conduit or metal wall. Really want that table completely isolated from its suroundings.

Argghh, I put a 4x8 foot sheet of galvanized sheet metal (20 gauge or 18) connected to the steel building supports (girts) and down to the floor and attached to a piece of angle iron secure to the concrete for protection of the insulation in front of the table. The table is pushed up against that so i know it it touching either the conduit and/or the grounded steel building. So it is best for me to move the table from touching my sheet metal? How far away from the sheet metal is correct to be done properly? The sheet is over the girt and behind the conduit. If I don't do anything what is the worst that can happen?
Thanks,
Grumple

[cruizer]

Hmmmm, are you serious, you've done pretty much everything completely wrong. where do I start.

Iif you leave it the way it is, you will NUKE your machine, and it wouldn't matter if it was a 250dx or $$ Dynasty

[cruizer]

Sorry for hijacking!! But, Cruizer -- since you mention you should not mount a receptacle to the table.......

I just built a cart for my Multimatic 200 and was thinking of mounting a box with 2 duplex receptacles, and a short male plug pigtail out of the box. That would allow me to plug the pigtail into an extension cord and provide me some 110V outlets for grinders, etc. 4 outlets would just be a convenience so I don't have to plug/unplug power tools. Only one would be used at a time. And, this outlet would have nothing to do with the power to my welder (other than it comes from the same house electrical wiring system) - it gets power from a dedicated 220V outlet. Will I have any type of problems with this arrangement??

Thanks -- and back to the OP's problem!!

You would need an isolated receptacle, it'll be safety orange, then sure, otherwise really bad things will likely happen

[Grumple]

Hmmmm, are you serious, you've done pretty much everything completely wrong. where do I start.

Iif you leave it the way it is, you will NUKE your machine, and it wouldn't matter if it was a 250dx or $$ Dynasty

I am glad I asked then. I have welded without any known problems on DC and just noticed the welding with AC seemed rough, or coarse, or ragged sounding so I thought it wasn't ideal. I haven't welded any aluminum until last week and I bought the machine in 2008. So let me take a pic of my setup tomorrow and post it so you can tell me the correct way to set it up. I don't mind making a fool of myself as long as others learn from my mistakes. Keep in mind I used to have a Miller Swinger 180 buzzbox and no welding table in the past and brazed with oxy/acetylene a lot. My Heliarc experience was at a workplace over 25 years ago so the machine was setup and I believe the walls were cement block behind it. Pics tomorrow...
Thanks,
Grumple

[Grumple]

Here are the pics of my setup. Let me know what is wrong and I will fix it.
Thanks,
Grumple

[cruizer]

AC will go nuts on that set up, DC will work adequate, it's an out of phase situation while welding on a non obsoleted table.

[Grumple]

AC will go nuts on that set up, DC will work adequate, it's an out of phase situation while welding on a non obsoleted table.

Cruizer,
Do you mean non-isolated table? What it the best way to fix? Remove sheet metal from behind table or move table out and isolate by placing 2x4 wood between sheet metal and table? What do you recommend? I mean what is the minimum distance I need to move the table from the direct contact with the sheet metal or conduit? Is 2 inches enough or is 6 inches enough to completely isolate it for AC welding?
Thanks,
Grumple

p.s. I welded a lot of DC TIG with no problems. Now I wonder if my PC1 card is ok if I isolate the table when welding in AC or HF mode, if the HLP-1 errors will stop or if the card is actually in need of repair?

[Broccoli1]

Sorry for hijacking!! But, Cruizer -- since you mention you should not mount a receptacle to the table.......

I just built a cart for my Multimatic 200 and was thinking of mounting a box with 2 duplex receptacles, and a short male plug pigtail out of the box. That would allow me to plug the pigtail into an extension cord and provide me some 110V outlets for grinders, etc. 4 outlets would just be a convenience so I don't have to plug/unplug power tools. Only one would be used at a time. And, this outlet would have nothing to do with the power to my welder (other than it comes from the same house electrical wiring system) - it gets power from a dedicated 220V outlet. Will I have any type of problems with this arrangement??

Thanks -- and back to the OP's problem!!

http://www.lowes.com/pd_145271-33536-C664502001_4294542238__?productId=1135915&Ns=p_product_qty_sales_dollar|1&pl=1&currentURL=%3FNs%3Dp_product_qty_sales_dollar%7C1%26page%3D2&facetInfo=

Mucho easier

[Grumple]

Isolated. How much in terms of inches or feet?

So based on my current setup and images provided, I am wanting to find out in terms of "isolating" my table from the wall or my welder etc that cruizer says will cause my machine to go crazy when welding in AC HF mode, how far away is enough space to isolate the table from the rest of the trouble making pieces? And the manual sure has some contradictions when it comes to grounding at least from what I read on the internet. They show a ground wire to earth ground connected to the welding table. I have my welding table pushed up against a steel building grounded frame so I thought in a sense it was grounded but its just bonded to the neutral through the conduit or steel building. So, should I just put casters on my welding table and when I want to weld just move the table away from the steel building bonded ground? Or should I move it away (and by how far) from the wall but connect an isolated earth ground with a new dedicated ground rod? I have a steel building so the last thing I want to do after I install my new $$$ PC1 Main Board, is fry it because I am grounded and not supposed to be, or fry it because I am not, and supposed be. ???
Thanks,
Grumple

[Sandy]

There gets to be a ton of confusion when we start blending different topics together when trying to solve any kind of problem.

There is a welding table, then there is the welding machine.

There are grounds, then bonds to grounds or things that are grounded.

In grounding systems there are single point grounding systems, then there are mesh (grid) grounding systems. Both of these are somewhat complex and in a open forum generally end up being a huge pizzing match over something as simple as terminology.

But let's talk connections only. A table or welding machine touching another piece of metal is not a connection, it is a potential for trouble. A piece of metal touching a metal beam that is touching concrete plus has sheet metal panels screwed to it that are touching numerous other pieces of metal that sooner or later touch a ground or something that is grounded is really asking for troubles. Or as previously mentioned, if the piece of metal or beam isn't bonded to anything then you may have just created an antenna that will not only transmit high freq but recieve as well. By the way, sheet metal screws with or without rubber washers screwed into painted surfaces do not qualify as [B]bonds[B]. A bolt into concrete that has rebar in it is not a [B]bond[B]. Rebar with mill scale and/or rust tied together with scaly rusty wire is not [B]bonded[B].

In our realm (the average guy like me) the most common means of taking measurements is with an ordinary VOM which does so using a small DC voltage source and a subtle DC current resulting in a reading of DC ohms of resistance. The issue you are trying to deal with is one of AC resistance called impedance shown with a symbol of a Z instead of the little horse shoe for DC ohms. While there are a few correlations that we have learned over the years where a certain reading of DC ohms will probably correlate to a similar value in impedance, it isn't something you can count on reliably. A case in point may be where two sharp edges of metal are pushed together and touching, an ohm meter may vary well give you a reading of zero ohms or a low resistance in ohms, but this joint will not pass higher currents in either AC or DC and probably not any of the high freq quite often associated with various welding or known high frequency operations in other realms. It is simply called a 'high impedance joint'. If it does pass high freq it will be in a choppy and inconsistent (arcing) manner.

Bottom line, if you really wanted to 'ground' a table for high frequency purposes, you'd be best off to clamp a substantial wire to the leg of the table and then clamp the other end to the electrical system grounding electrode. As a substitute to that you could clamp to a metal beam that is continuous to a point near the electrical system grounding then bond from that to the electrical system grounding electrode. This would be more consistent with a single point grounding system. But then you haven't addressed the welder coincidentally touching the table. The welder has it's own grounding wire back to the electrical system grounding electrode, and it would be of a slightly different potential. See how this just never ends. When you start to enter the perfect world a ton of nearly impossible hurdles start popping up. The hurdles can only be cleared with time, effort and money.

Just some random thoughts.

[Grumple]

There gets to be a ton of confusion when we start blending different topics together when trying to solve any kind of problem.

There is a welding table, then there is the welding machine.

There are grounds, then bonds to grounds or things that are grounded.

In grounding systems there are single point grounding systems, then there are mesh (grid) grounding systems. Both of these are somewhat complex and in a open forum generally end up being a huge pizzing match over something as simple as terminology.

But let's talk connections only. A table or welding machine touching another piece of metal is not a connection, it is a potential for trouble. A piece of metal touching a metal beam that is touching concrete plus has sheet metal panels screwed to it that are touching numerous other pieces of metal that sooner or later touch a ground or something that is grounded is really asking for troubles. Or as previously mentioned, if the piece of metal or beam isn't bonded to anything then you may have just created an antenna that will not only transmit high freq but recieve as well. By the way, sheet metal screws with or without rubber washers screwed into painted surfaces do not qualify as [B]bonds[B]. A bolt into concrete that has rebar in it is not a [B]bond[B]. Rebar with mill scale and/or rust tied together with scaly rusty wire is not [B]bonded[B].

In our realm (the average guy like me) the most common means of taking measurements is with an ordinary VOM which does so using a small DC voltage source and a subtle DC current resulting in a reading of DC ohms of resistance. The issue you are trying to deal with is one of AC resistance called impedance shown with a symbol of a Z instead of the little horse shoe for DC ohms. While there are a few correlations that we have learned over the years where a certain reading of DC ohms will probably correlate to a similar value in impedance, it isn't something you can count on reliably. A case in point may be where two sharp edges of metal are pushed together and touching, an ohm meter may vary well give you a reading of zero ohms or a low resistance in ohms, but this joint will not pass higher currents in either AC or DC and probably not any of the high freq quite often associated with various welding or known high frequency operations in other realms. It is simply called a 'high impedance joint'. If it does pass high freq it will be in a choppy and inconsistent (arcing) manner.

Bottom line, if you really wanted to 'ground' a table for high frequency purposes, you'd be best off to clamp a substantial wire to the leg of the table and then clamp the other end to the electrical system grounding electrode. As a substitute to that you could clamp to a metal beam that is continuous to a point near the electrical system grounding then bond from that to the electrical system grounding electrode. This would be more consistent with a single point grounding system. But then you haven't addressed the welder coincidentally touching the table. The welder has it's own grounding wire back to the electrical system grounding electrode, and it would be of a slightly different potential. See how this just never ends. When you start to enter the perfect world a ton of nearly impossible hurdles start popping up. The hurdles can only be cleared with time, effort and money.

Just some random thoughts.

Sandy,
Thanks for chiming in here with your thoughts. My main and most important question is how far should my welding table be from any possible problem causing interference when doing AC HF aluminum welding? My pics show my current setup and my table is probably touching the galvanized sheet I put on the steel building frame to keep hot sparks from damaging my insulation. To avoid any HF damage to my welding machine (which will never ever touch my welding table), how far away should be a minimum that the welding table is away from any steel building parts that may or may not be bonded/grounded etc? Could I put a piece of wood like a 2x4 between my welding table and the sheet of galvanized metal that is connected to my building frame and be good, or would it be better to move my welding table 5 to 10 feet from the wall? I am just unsure if the HF can cause a problem by being close to the steel building wall or if the problem occurs when the table is touching or almost touching by being so close it can arc between the two? How about I just put in a new separate earth ground rod and connect to the welding table and move the welding table away from the wall by 1 foot?
Thanks,
Grumple

[Sandy]

Grumple,

I'm with the 'no separate ground rod' crowd. Besides violating the NEC intent there can be other issues. Not that a drain electrode might not solve an issue every now and then on a temporary scale, there are just too many other potentials when things like that get left as part of the installation. As far as 'isolating' the table, total isolation isn't real practical as long as you are setting on a concrete floor but it would be best to try to get rid of any coincidental and/or potential coincidental contact with all the unknown metallic objects. Especially those electrical conduits and such. That could be accomplished with only inches to feet. What ever you like. Whatever you think will lesson the chance of coincidental contact.

I've always questioned how grounding the table really plays into a high freq issue as far as saving the machine goes other than the manufacturer is telling the user to provide a drain wire. Drain wires are common in the high freq world but are always incorporated into the design and in conjunction with all applicable electrical codes rather than in violation of.

In my mind the manufacturer needs to either write a solution that is in tune with all other equipment of this nature or harden up the machine. If interference with other equipment is some folks concerns,,, then a good clean single point grounding system is the real answer. Mesh grounds can be hard to maintain and usually end up with a current carrying ground loop somewhere.