How Do You Ground a Welding Table?
When setting up a welding circuit, you know that clamp that you call a grounding clamp? Don’t call it a grounding clamp. Call it a “return” clamp, because it returns the current to your welder. That differs from an earth ground. An earth ground makes a physical connection to the ground via a conductive material. Your metal welding table should have an earth ground.
How do you ground a welding table? You ground a welding table by connecting a wire to a ground rod or to an already-grounded structure, like a metal shop building.
Some would say you waste your time with this step, as the grounded power plug of the welder supplies sufficient grounding. Maybe so, maybe no.
But let’s look at another term requiring an adjusted mindset – “sufficient.” You don’t want “sufficient.” You want “best.” Or “safest.” Electricity dances like lightning in a summer thunderstorm when you weld. You don’t want to get picked as its dance partner.
Is the Ground the Ground or is the Welder The Ground?
Electricity constantly runs to the ground, where negatively-charged electrons seek balance among positively-charged protons, found in the greatest abundance in the earth’s surface. There exists no better example of the balance of nature than this. When lightning flashes, followed by a mighty clap of thunder, think of it as zillions of electrons seeking balance.
The same principles apply to your workshop. Whether you use a power saw to cut 2x4s or a welder to join steel, the electricity wants to run to ground. That makes current move in the first place. The difference is, when using a power saw, the saw does the work. In welding, the electricity does the work. It is the work.
Modern welders – as do modern just about anything – come with a grounded plug. The round tip connects to the house or shop’s grounding circuit and sufficiently grounds the unit. This way, the welder protects itself against short circuits.
But consider the whole project – the work, the welder and the human doing the welding. In a welding circuit, the welder serves as the “ground.” That may be a bad choice of words but that’s what it’s called. And the welder is separately grounded to the earth. In that application, the earth is the ground.
A Freestanding Welding Table is not the Ground
A heavy metal welding table, freestanding, not connected to an earth rod, should never be considered as “the ground.” It acts as part of the welding circuit. And as a large conductive hunk of metal, serves as an important part of the welding circuit. Laying metal work pieces on it, or clamping the lead to it gives those balance-seeking electrons somewhere to go.
Without intervention, a welding circuit remains isolated from earth ground. Yes, the welding circuit is connected to a welding machine, and the welding machine is grounded, but the grounding is for its own protection.
Even if connected to earth rods or a suitable metal structure, a welding table still does not serve as the ground for the welder itself. It’s already grounded. When you ground the table, you provide actual earth grounding for the welding circuit.
What Does the ANSI Say About Grounding a Welding Table?
The American National Standards Institute says that the grounding of work pieces, equipment housings, metal cabinets, frames or other conductive material that forms part of the equipment limits the voltage to ground on those items. Limiting the voltage by grounding helps prevent accidental shocks when equipment is misconnected or insulation fails. (ANSI Z49.1 E188.8.131.52)
Additional reasons for grounding a metal welding table to earth exist, such as when using high-frequency arc stabilizers. This protects sensitive electronic gear that may be in the vicinity.
Increasing the number and conductivity of additional paths to ground limits the likelihood that your body will become a path to ground. After all, you stand as the most important element in this process!
Pounding earth rods into the dirt, or using power equipment to force eight-foot long metal rods into rocky soil is no picnic in the park. And while we don’t think grounding your welding table is overkill, making a separate, dedicated wire run strictly for this purpose probably is.
Connecting your table to the ground system in your home can be accomplished in a number of ways, but take the simplest way. A heavy wire – 4-gauge insulated copper makes a good choice – connected by grounding lugs to the home’s ground wire works just fine.
If you want to run a separate ground wire to an earth rod, you certainly can, if for some reason you can’t easily access the regular ground wire. Just follow established practices and electrical codes.
“Sticking Out” Rebar Grounding
Many modern homes are grounded, not to earth rods, but to the rebar that’s embedded in the concrete foundation. The contractor leaves a rebar exposed to the outside – informally referred to as “sticking out” and bent upward. The grounding electrode conductor then clamps onto the exposed rebar.
While direct contact with the soil is less than with earth rods, the matrix of connected rebars has enough metallic mass to provide grounding for household needs. But, as the earliest houses to be wired this way have reached into their 20s, problems have arisen. Corrosion and rust, at the point where the grounding conductor attaches to the rebar, have weakened the overall conductivity of the grounding system.
The technique remains legal in many jurisdictions, but many governing boards want to take a second look at the practice.
Whether this should force you to go to an earth rod system for grounding your welding table is not known.
Grounding to Pipes
It used to be standard practice to use a metal water pipe as a ground electrode. It still functions as an acceptable practice, but the National Electrical Code (NEC) has added some restrictions. The biggest of those restrictions states that if you use a metal water pipe as a grounding electrode, you must install a second, conventional electrode.
In addition, the NEC has added these additional requirements:
10 feet of water pipe must be in direct contact with the earth
Joints must be electrically continuous
Water meters must not be relied on for the grounding path
Bonding jumper must be used around insulating joints, pipes or meters
Primary connection to the water pipe must be on the street side of the water meter
Primary connection to the water pipe must be within five feet of the point of entrance to the house or building
The best advice here is not to rely on water pipe grounding. The issues of corrosion, plus the use of plastic fittings that break the conductivity of the pipe make this a grounding technique not worth the effort.
Tell Me Again Why I Would Want to do This
Your work makes a complete circuit. Your welder’s ground wire goes to a grounded receptacle. You’re wearing long sleeves. You’re dry. The table is dry. Your clamps are clean. The spot at which they’re attached is clean. Why bother to ground the metal table?
We never said the danger of getting a shock from an ungrounded table constitutes a likely event. It doesn’t. But what we say give the current an additional path to ground, one that could be the path with the very least amount of resistance. If any of those situations in the preceding paragraph become compromised in any way, or if something goes haywire inside the welder, that extra layer of protection can provide peace of mind.
This extra layer of protection helps you, primarily, but it can also spare your work from damage in the case of a stray arc.
Work Circuit Reminders
Having a constant, consistent circuit while welding is at the heart of any project. Every component, from the work, to the welder, to the clamps to the stinger depends on the others. The cliché, “A chain is only as strong as its weakest link” applies profoundly to your work circuit.
Check off the things on this list before starting any welding project. If you work as a full-time welder on a work shift, you should check these things at the beginning of every shift. Traveling welders should check these items off every time they relocate to a new job site, and then every day while working at that site.
Weekend welder or a part-timers should start every project with a check of the things on this list:
- The connection between the welder and the gun’s cable plug
- The fittings and connections between the gun’s power cable and the: Neck, Diffuser, Contact tip, Welding wire, Set screws, Compression fittings, Crimped connectors, Work clamp, Cables
Be a Clamp Champ, Not a Clamp Chump
Other than the gun tip, the clamp is the component most moved about in a welding session. It also fails – probably – more often than any other component in the circuit. Clamps wear out over time, develop pits or gaps, the springs lose their springiness and the connectors loosen.
When in good working condition, the clamp creates a solid, strong electrical connection with as much metal-to-metal contact as possible. Good clamps do this use after use, day after day. Cheap clamps aren’t worth the cost from Day One.
Look for these issues with your clamp(s):
- Loose cable post
Check the lug nut for tightness with a wrench, not your fingers.
- Make sure the threads aren’t stripped.
Make sure the metal surfaces that touch are clean and not pitted.
- Frayed or damaged lead wire
Every strand of copper that pulls away from the others means that metal that isn’t making contact.
Gaps in insulation spell trouble, even if the wire itself seems fine. Don’t mess around. Replace the cable. No amount of electrician’s tape will adequately fix this problem.
- Pitted or gapped handles or jaws.
Your welding circuit sustains a lot of current and a lot of heat, and the clamp often pays the price. The more damage it sustains, the more likely damage occurs, because the resistance creeps up with every loss of metal.
Look for damage to the connector that runs between the jaws of the clamp. You’d be surprised at how often this part fails.
- Grip Strength
The clamp should be slightly difficult to open, kind of like those muscle-building devises you squeeze. If it offers little resistance to the squeeze, it’s probably too loose for a secure connection.
The Welding Gun
- The cable connection
Tighten compression settings down firmly. If they won’t tighten down all the way, replace them.
Set screws can easily back out of position. Tighten them to manufacturer specifications.
Crimped fittings provide excellent connectivity, but can sustain damage, so watch for pitting or deterioration.
- The welding tip.
This is where the action is, and it could be where the trouble is. The connection here must be absolute and unwavering.
When metal touches metal, there should be nothing that comes between the two. Oil, grease, rust, corrosion, torched bits of metal, dirt, paint, plastic and dust compromises the electrical connections. Clean, clean, clean. Clean the table, if you lay work on it and make it part of the circuit, clean the work where you clamp it, and clean the jaws of the clamp.
You can use solvents, but often steel brushes and grinding wheels make your surfaces as bare as bare can be.
Two key things to remember about electricity in a welding circuit. You need to know (1) The current’s source, and (2) The current’s destination. Once set on those two elements, you can easily remember rule No. 3 – Don’t stand between 1 and 2. Make sure your “grounding clamp” and your work sit next to each other, and don’t stand in the middle.
Moisture, the bane of any electrical circuit, should be avoided at all costs. Your sweat is moisture too. Sweat a little, lean up against the metal welding table, and feel the tingle (or worse) in your bones. Stay dry, wear long sleeves, non-conducting shoes, and no wristwatches, bracelets or metal necklaces.