PDA

View Full Version : How to ground your welder?



NewLou
20th Oct 2007, 08:38 AM
Gidday:)

Making sure your welder is grounded appropriately is essential Heres a good introductory article from the Lincoln Website:

http://www.lincolnelectric.com/knowledge/articles/content/grounding_arc_welding_safety.asp

Wanted to bring this one up as an issue particularly in the age of highly portable inverter units!

It's really worthwhile considering issues like:

How do i ground my welding table?

Whats the best way to ground my inverter (Is this necessary?)

What do I need to consider when looking at grounding my 'Rig'?

.................Hopefully Grahame will give us a few more pointers on this one!

REgards Lou:2tsup:

BobL
21st Oct 2007, 01:29 PM
A key paragraph on that web page.

"According to ANSI Z49.1, "Safety in Welding, Cutting and Allied Processes," the workpiece or the metal table that the workpiece rests upon must be grounded. We must connect the workpiece or work table to a suitable ground, such as a metal building frame. The ground connection should be independent or separate from the welding circuit connection."

At work we have a grounded table and the way to check that your piece(s) are grounded is to connect the welder clamp to the table rather than the piece and clamp the pieces to the table or a vice mounted in the table. Then if you can strike an arc on the piece the pieces should be grounded. Must make myself a ground for home some time. I saw the sparky used a star picket driven about 4ft into the ground for our extension. Might do the same for the shed - has anyone else done this?

martrix
21st Oct 2007, 01:39 PM
Might do the same for the shed - has anyone else done this?

Crikey, I better look into this. At the moment I just use a stainless bench on a steel frame that sits on the dirt. Is that a good enough ground?

BobL
21st Oct 2007, 04:31 PM
Crikey, I better look into this. At the moment I just use a stainless bench on a steel frame that sits on the dirt. Is that a good enough ground?

Err . . . no, especially if the dirt is dry.

A welder is an "usual tool" in that it has a conductive path direct into the guts of the machine. The grounding of a bench is a safety precaution against something going wrong inside the welder and the 240V somehow connects itself to clamp line. When you thus pick up the clamp and get zapped. It would be nice to ground the rod holder as well but then the welder wouldn't work. Most people will not bother with doing this and live very successfully. Also it is not always possible to do when working on vehicles or buildings etc However, seeing as it takes very little effort to do for a stationary bench it is probably worth doing.

Vernonv
21st Oct 2007, 05:52 PM
I saw the sparky used a star picket driven about 4ft into the ground for our extension. Might do the same for the shed - has anyone else done this?

I wouldn't. Star pickets are not the best way to earth anything ... I would go to the local electrical supplier and get an 1800mm copper clad earth rod and clamp (and wire if you need it). Also I think your shed (if it's steel) should already be earthed (i.e. connected to the electrical earth and therefore an earth rod) so you might just be able to connect the bench to the steel structure of the shed.

Mick C.
21st Oct 2007, 09:14 PM
I bet theres a rule that says your sparky shouldnt have used a star picket! And him putting in a second one rather than useing the original doesnt sound right either (well not when talking about the one building) Multipul earths will creat a "potential difference" between the earth stakes and thus a voltage difference between the various earths in the building... i guess if they are joined together it may be ok, but i dont think its normal practice...

Grahame Collins
22nd Oct 2007, 12:00 AM
Guys,
I would be more inclined to direct my efforts in favour of the electrical/mechanical connections of your earth return and electrode cables. For those who have not had a boot off the welder its like touching the spark plug when the mower is going.

Usually when someone gets a boot it is usually a result of a poor connector somewhere in the secondary cables..The welding current is trying to take a short cut home.

Because we move our cables around-crikey some even wrap their cables up when finished- the connectors move ever so slighty. Looseness causes a resistance heat build up which makes the problem yet worse again.

The modern taper twist pins dont suffer this problem.If you have an older bolt up connection system check that on a regular basis.

Crappy A frame earth clamps that are weak springed because of heat damage, need replacement.They are the cause of more than a few welding problems as the weak connection does not allow full current through the work.
Wherever you can clamp directly to the work.

The job if sitting on spatter balls doesn't get full electrical value.

Twist grip electrode holders made of bakelite type plastic wear and crack so it possible to to get a metal to skin connection there. pull them apart and tighten them up periodically and or replace.

Check your gloves for cracks and dampness.

Place an insulator mat on the floor a bit of conveyor belt is good.Did you know dry concrete can conduct enough current to do you a nasty- The Tafe electrician teachers showed me that one.

Finally it is the micro amps that do the damage.If you have suffered a boot get a check up pronto.it is possible to suffer a heart attack within 24 hrs

And of course wear your boots_ I said boots not thongs aye!

Grahame

BobL
22nd Oct 2007, 12:21 AM
I bet theres a rule that says your sparky shouldnt have used a star picket! And him putting in a second one rather than useing the original doesnt sound right either (well not when talking about the one building) Multipul earths will creat a "potential difference" between the earth stakes and thus a voltage difference between the various earths in the building... i guess if they are joined together it may be ok, but i dont think its normal practice...

I agree on the two earths and the fact that this can set up ground loops BUT I'm not talking about a second electrical circuit earth but actually earthing a welding table.

BTW the star picket was also not a second earth but it replaced the old one which was loosely bolted to a sheet metal sewage vent/chimney that had almost rusted through and was in danger of not even being connected to the ground! Someone, a house owner?, had also connected an earth to the copper mains plumbing! Heaven knows when any of this was done as the house is nearly 100 years old. The wiring is our house was a mix of new and old cloth and rubber coated wire. The house had supposedly been rewired before we moved into it in 1978 but every time I went up into the ceiling space I came down with 10's of metre of old cloth and rubber coated wire. In 1994 we had the house completely rewired from scratch and that was when we had the new earth put in.

BobL
22nd Oct 2007, 12:34 AM
Finally it is the micro amps that do the damage.If you have suffered a boot get a check up pronto.it is possible to suffer a heart attack within 24 hrs


Saw a guy getting a 415V boot a couple of years back. He was thrown to the floor like a wrestling throw - fortunately it flung him clear of the exposed cable and he seemed OK. We tried to get him to go to see a doctor but he refused and being a sort of loud mouth character that never stopped talking after the shock he went silent so we knew he was not OK. After about half an hour or so of his shock he disappeared and we thought he might go home so we called his missus and explained what happened. She hauled him out of bed and down to the hospital. It turned out he had these strange internal burns and eventually vomited blood and he was in hospital for a week and off work for another 2. Not nice.

ds2006
8th Nov 2007, 01:57 PM
Most industrial generators that we hire for outdoor gigs come with a star picket earth stake. The reason being that copper is just too soft to repeatedly hammer into the ground and get out again. Obviously it is the best choice but a star picket is better than nothing.

The main thing is that the earth stake is in an area where the soil is moist and this is why the standards say it must be placed in an exposed area. When I water the garden in summer, I also water the earth stake (not expecting it to grow) but to reduce resistance caused by dry soil. In some instances, it is necessary to add salt the the water to ensure that the conductivity is good.

I remembered when I wired up my workshop, I asked the sparky who came to certify my work and do the final connection to the mains if I should put in an earth stake or not. He said as the workshop is only 30m from the house, it was not necessary. There are some issues regarding multiple earth stakes but I cannot remember if this just relates to MEN bonding (settle down ladies) which is the point at which the neutral and earth are bonded. The MEN (Main Earth Neutral) bond should only be done once as far as I can recall. However, this was a few years back and I cannot remember the full details. Electricity kills (commonly a few days after a jolt), so when in doubt call a local sparky.

Fossil
8th Nov 2007, 03:44 PM
Finally it is the micro amps that do the damage.If you have suffered a boot get a check up pronto.it is possible to suffer a heart attack within 24 hrs


I spent all of last long weekend in hospital after a suspected heart attack.
I am still getting tests done to find out what's going on, as the Cardiologist cannot explain why such a fine example of a man such as myself is getting the heart pain. I beleive it is probably my very high intake of red wine, and salt to keep my blood pressure up that saved me. My doctor doesn't agree. :roll:

I weld up stuff at least weekly, and am regularly zapped for one reason or another. Usually when I kneel down on one leg to weld up something in a difficult position, and I get zapped through the ground.

Do you have more info Graham?
I've been stick welding since I was a kid, and never heard of that, although I am self taught, so haven't done any safety training.

Thanks.... I don't want to die just yet.

Gra
8th Nov 2007, 03:52 PM
how do you ground half a dozed bricks, placed on a brick floor???

Well thats what we use as a welding table:no:

Fossil
8th Nov 2007, 03:53 PM
I remembered when I wired up my workshop, I asked the sparky who came to certify my work and do the final connection to the mains if I should put in an earth stake or not. He said as the workshop is only 30m from the house, it was not necessary.

He is technically correct however it is often cheaper, and is certainly safer to whack an earth stake in at the base of your sub-board at the workshop end. Often cheaper, beacause you don't have the cost of an extra earth wire back to the house board, which may mean you can use smaller diametre conduit as well if that is what you need. Safer because earthing efficiancy is all about resistance, or more accurately... lack of resistance. The closer the earthing point is to the machines that you are running in the shed, the better chance the operator has of not copping the full whack of current, should there be a fault or accident. Induction motors, lights etc etc, all work perfectly without an earth, but everything in your shop, except double insulated portable devices, should be properly earthed. My brother is a sparky. I always wire up everything, and Gelnn checks it out before service is comissioned. We always check all earths first, measuring impedance (or lack of), and get that side sorted first.

Grahame Collins
8th Nov 2007, 05:46 PM
Hi Fossil,
I think the issue of not becoming part of the circuit is of a larger problem that the earth of the table itself.

An rubber mat and proper safety boots or shoes all play their part in separating you from the current.Same goes for good tight electrical connections. Cabling moves and connections loosen up.
I see the kids at school get booted and blame the electrical integrity of the machine when it isn't so.

Leaning on the machine, damp gloves (cos they insist of taking a red hot coupon to the trough and they get wet) all create conditions that can cause the operator some problem.

Improper mechanical/electrical connections in the earth clamp to cable or cable to terminal.
If the earth connection is not allowed to earth it wants to take a short cut -THROUGH YOUR BODY.

Minimize the possibilities of bad earthing by:

Rubber or cork insulation mats
Good footwear.
Good cabling connections


Grahame

BobL
8th Nov 2007, 11:07 PM
Grahame, I don't know a lot about welding but I know a shirt load about electricity. Relying on rubber mats and boots alone to not get a boot is not good OHS policy and often physically makes no sense either.

Touching a live circuit with one hand while holding onto anything that's even 1% earthed with the other hand means the electrickery is gonna pass that way (ie right across your heart) and no amount of rubber matts or boots will help. People think they are invincible in rubber boots and they generally do not make up for other problems.

I once accidentally stuck my hand inside a bit of electronics gear and had 6000 V hit the tip of my ring finger. The current ran half way down that finger to a point where it was touching a grounded metal cabinet. There was a loud bang, I got thrown half way across the room and my finger turned a green purple over a couple of days. I had rubber soled boots on - didn't help at all. Just as well my finger was also touching the grounded cabinet because my heart was probably next in line.

Cliff Rogers
8th Nov 2007, 11:24 PM
2 bob from another bloke who knows a bit about electrons....

Don't try using 6000volts to weld with. :D

Wild Dingo
9th Nov 2007, 01:13 AM
mmmmmm soooooooo now what with the wang dang doodle of a mig welder Ive got hidden in the unpowered shed am I in the nooah or what? I simply run an extention lead the 50mtrs to the shed plug in and away I go.

I was taught stick welding very basically by an old farmer fella up north and was told that as long as the clamp thing has a good clean clamp it would be right? so this is wrong?

Grahame Collins
9th Nov 2007, 06:57 AM
People think they are invincible in rubber boots and they generally do not make up for other problems.

Hi Bob
You are quite right.Passage of current across the body and through the heart is not a good thing.

I certainly hope readers do not think I am implying that rubber boots alone are the answer.They were but one of a number of precautions listed.

As someone who supervises students ,I take the attitude that all have the potential to be electrocuted and accordingly instruct them in all precautions as outlined in my posts.

I trust people take on board, all of what is written and apply it their situations.Being an instructor I get the feedback on those types situations from my students, in and out of the training workshops where my students had received a boot.Where it occurred I house (at TAFE ) I always investigated.

In twenty years I was only ever involved in one serious hit where a student from another class was hit.He was dripping wet from perspiration from playing footy at lunchtime in the stifling NT humidity.

Apparently he leaned against the steel bench and struck the electrode which stuck to the bench. He then reefed ithe rod loose and it unstuck and him dead center in the forehead. Not only did the current travel through his torso but through his head.
His symptoms were eyes like pinpoints and his skin the colour of cement. Fortunately after a night in hospital he suffered no ill effects.


I believe the regimen of asking students to physically check the quality of the earthing -checking the tightness of the terminal connections before switch on - prevented many problems. Because of the nature of the work, cabling connections become loose on those machines with removable connections.

This was only one of a number of precautions taught.
As an aside Bob ,we discourage our metal tradesmen form wearing rings for a very different reason. Catch a ring on a heavy sheet and it can strip the meat clean off the bone.


Work safe
Grahame

BobL
9th Nov 2007, 11:39 AM
Good post Grahame! :2tsup:


In twenty years I was only ever involved in one serious hit where a student from another class was hit.He was dripping wet from perspiration from playing footy at lunchtime in the stifling NT humidity.

Apparently he leaned against the steel bench and struck the electrode which stuck to the bench. He then reefed ithe rod loose and it unstuck and him dead center in the forehead. Not only did the current travel through his torso but through his head.
His symptoms were eyes like pinpoints and his skin the colour of cement. Fortunately after a night in hospital he suffered no ill effects.
:oo: :U :C :D - I can just imagine this happening!


As an aside Bob ,we discourage our metal tradesmen form wearing rings for a very different reason. Catch a ring on a heavy sheet and it can strip the meat clean off the bone.

Reminds me of when my brother fell off a horse and the stirrup buckle caught on his wedding ring and the ring cut his finger clean off - they never found his finger!

Talking about connections - I looked claosely at my cheapie welder last and noticed how sloppy everything looked so I've replaced the cheap cables, connectors and the handpiece, which was cracked and starting to fall apart from falling on the floor a couple of times. I really like the feel of the new stuff - it's all a lot heavier and hopefully should reduce the shake problem.

BobL
9th Nov 2007, 11:42 AM
mmmmmm soooooooo now what with the wang dang doodle of a mig welder Ive got hidden in the unpowered shed am I in the nooah or what? I simply run an extention lead the 50mtrs to the shed plug in and away I go.

I was taught stick welding very basically by an old farmer fella up north and was told that as long as the clamp thing has a good clean clamp it would be right? so this is wrong?

50 mtrs - wow that is a long way - I'd be seriously grounding my work and workbench at that distance.

elkangorito
10th Nov 2007, 06:25 AM
"According to ANSI Z49.1, "Safety in Welding, Cutting and Allied Processes," the workpiece or the metal table that the workpiece rests upon must be grounded. We must connect the workpiece or work table to a suitable ground, such as a metal building frame. The ground connection should be independent or separate from the welding circuit connection."

I would just like to point out that even though "earthing" (not "grounding") your work table may be a good idea, the standard mentioned (ANSI Z49.1) is an American standard & refers to the American electrical code (NEC). The American electrical system is vastly different to that of the Australian system. Unless Australia has decided to adopt this standard for "Normative" use, it does not apply.

Also, "earthing" is not a simple subject. In fact, it can be very dangerous if not done correctly. Multiple earths used in the MEN system, must conform to the Australian standard of wiring rules (ASNZS 3000:2000). The placement of anything other than an appropriate earthing electrode, can be very dangerous. The use of steel fence posts as temporary earthing electrodes is not safe. Infrequently "watering" a ferrous earthing electrode may speed up the oxidisation process of the electrode (rust) & therefore make it useless & even dangerous, particularly if salt water is used.

Not all electric arc welders are the same. Depending upon their individual design, earthing may or may not be required. Eg if the unit is Class 2 (double insulated), no earthing is required. If the unit is enclosed in metal, the supply cable should earth the unit chassis to the main earth via the distribution board.

If "work tables" are earthed, it should either be done by;

1] a connection to the existing installation main earthing system at the distribution board, or;
2] an extra earth electrode that is connected & tested in accordance with ASNZS 3000:2000.


The 1999 edition of ANSI Z49.1 can be downloaded from;

http://www.aws.org/technical/facts/Z49.1-1999-all.pdf

dennford
10th Nov 2007, 08:46 AM
This is all very interesting but not being an electrician I don't think that I shall ever touch a welder again after reading all the above. That is unless someone can explain in simple terms (I do simple very well) Why I shouldn't just earth my workpiece to the welder and using common sense safety procedures just merrily deposit gobs of metal on the parts I am trying to join.

Do I run a second earth from my bench/workpiece to the earth on my power supply?

BobL
10th Nov 2007, 11:46 AM
This is all very interesting but not being an electrician I don't think that I shall ever touch a welder again after reading all the above. That is unless someone can explain in simple terms (I do simple very well) Why I shouldn't just earth my workpiece to the welder and using common sense safety procedures just merrily deposit gobs of metal on the parts I am trying to join.

Do I run a second earth from my bench/workpiece to the earth on my power supply?

If your shed electricals have been installed by a licenced electrician then there is no need to really do anything other than continue to use common sense. Any risk you run is a lot less than other daily stuff like driving your car.

"Do I run a second earth from my bench/workpiece to the earth on my power supply?" I would not touch existing earth circuits or connections.

Unfortunately I have used the phrase "earthing the bench" in my earlier posts which is confusing because some members are taking this to be what you said. I will henceforth call "earthing" to mean, "connected to the household/shed electrical circuit earth" and "grounding" as being directly electrically connected to physical ground. Grounding your bench provides a measure of safety and avoids the ground loops being discussed.

If your shed is more than ~30 m from your house your electrician should have thought about adding a small breaker box and possibly a new earth circuit stake near the shed. Grounding the bench in this situation is still an independent proposition that does not involve the electrical circuit earth.

BTW If you have a metal bench and you test the continuity between your bench and electrical circuit earth and you get an open circuit this is no guarantee that your bench is not at least partially earthed. A conventional multimeter cannot perform a proper AC electical continuity test - this requires a special ~$500 AC continuity meter. A partially earthed/grounded bench is in principle more dangerous (still safer than driving your car) than a fully grounded bench.

Now just to confuse matters, what about if you are using a generator to power a welder?

journeyman Mick
10th Nov 2007, 02:58 PM
Well, what if you are using a genny to power your welder, or you're welding in a remote location with a weldanpower unit. For that matter, when I'm using a generator for power and I plug a non double insulated tool into it is there anything I should be doing? (besides using a RCD board)

Mick

elkangorito
10th Nov 2007, 09:55 PM
If your shed electricals have been installed by a licenced electrician then there is no need to really do anything other than continue to use common sense. Any risk you run is a lot less than other daily stuff like driving your car.

"Do I run a second earth from my bench/workpiece to the earth on my power supply?" I would not touch existing earth circuits or connections.

Unfortunately I have used the phrase "earthing the bench" in my earlier posts which is confusing because some members are taking this to be what you said. I will henceforth call "earthing" to mean, "connected to the household/shed electrical circuit earth" and "grounding" as being directly electrically connected to physical ground. Grounding your bench provides a measure of safety and avoids the ground loops being discussed.

If your shed is more than ~30 m from your house your electrician should have thought about adding a small breaker box and possibly a new earth circuit stake near the shed. Grounding the bench in this situation is still an independent proposition that does not involve the electrical circuit earth.

BTW If you have a metal bench and you test the continuity between your bench and electrical circuit earth and you get an open circuit this is no guarantee that your bench is not at least partially earthed. A conventional multimeter cannot perform a proper AC electical continuity test - this requires a special ~$500 AC continuity meter. A partially earthed/grounded bench is in principle more dangerous (still safer than driving your car) than a fully grounded bench.

Now just to confuse matters, what about if you are using a generator to power a welder?

The earthing of metallic work benches is considered to be a part of Equipotential Bonding, which is supplementary to the Protective Earthing system. Australian Standards say that the "Bonding of extraneous conductive parts and their connection to the earthing system may be used to reduce the fault-loop impedance in order to ensure that the disconnection time of the protective device is sufficient..."

Please note the words "bond" & "earthing system". This means that if you wish to earth your metal work bench, it must me done with the use of a cable that is connected to the Main Earth bar in the distribution board. Using an extra earth rod (electrode) will not fulfil this requirement unless it can be proven (by testing) that the complete Earth Fault Loop impedance from the work bench & back to the Main Earth electrode is such that it will not impede the operation of any protective devices (fuses, RCD's & circuit breakers).

In general, Equipotential Bonding arrangements are intended to minimize the risk associated with the occurrence of voltage differences between exposed conductive parts of electrical equipment and extraneous conductive parts.

Your welding unit should already be earthed via its' supply lead.



Well, what if you are using a genny to power your welder, or you're welding in a remote location with a weldanpower unit. For that matter, when I'm using a generator for power and I plug a non double insulated tool into it is there anything I should be doing? (besides using a RCD board)

Mick


A good question Mick.

As per Australian Standards, a portable generator that is in no way connected to your domestic electrical system is deemed as being "electrically separated" & as such, does not require any "extra" earthing.

"Protection by electrical separation is intended, in an individual circuit, to prevent shock current through contact with exposed conductive parts which might be energized by a fault in the basic insulation of that circuit."
The above paragraph basically says that the electrically separate device does not utilise an "earth return" path & therefore, an earth is redundant (or dangerous). The M.E.N. system does use an earth return & so earthing is critical with it.

Further;
"The source supplying a separated circuit shall be —
(a) an isolating transformer complying with AS/NZS 3108; or
(b) a source of current, e.g. a motor-generator set or uninterruptible power supply, that is selected and installed so that the output is separated from the input by double insulation or equivalent."

Also;
"Where a separated circuit supplies a single item of electrical equipment, any exposed conductive parts of the electrical equipment shall not be connected to the exposed conductive parts of any other circuit, including other separated circuits."


In a nutshell, do not provide any "extra" earthing for any part of your generator. You must, however, use an appropriate RCD.

"Ensure that all portable generators comply with AS 2790, 1989 as amended Electricity Generating Sets - Transportable (up to 25 KW). Ensure that the power supply for all construction wiring emanating from a portable generating set complies with this Code of Practice including protection by a core balance earth leakage device with a rated tripping current not exceeding 30mA." (Workcover - Codes of Practice - Electrical Practices for Construction Work).

dennford
10th Nov 2007, 10:33 PM
"Bonding of extraneous conductive parts and their connection to the earthing system may be used to reduce the fault-loop impedance in order to ensure that the disconnection time of the protective device is sufficient..."

Please note the words "bond" & "earthing system". This means that if you wish to earth your metal work bench, it must me done with the use of a cable that is connected to the Main Earth bar in the distribution board. Using an extra earth rod (electrode) will not fulfil this requirement unless it can be proven (by testing) that the complete Earth Fault Loop impedance from the work bench & back to the Main Earth electrode is such that it will not impede the operation of any protective devices (fuses, RCD's & circuit breakers).

In general, Equipotential Bonding arrangements are intended to minimize the risk associated with the occurrence of voltage differences between exposed conductive parts of electrical equipment and extraneous conductive parts.

Your welding unit should already be earthed via its' supply lead.




I realise that I am not the only one on this thread but please my request for simple was a little tongue in cheek and although I know that a thorough understanding of any subject does require some technical jargon, surely to qualify this with a simplistc explanation would help myself and others to understand. After all I would presume that anyone who can understand what you're talking about with all those long and unfamilliar words would not need preaching to - it's us simple folk that need the preaching, but what is the use of preaching if we can't understand your language?

Denn (once again confused)

elkangorito
10th Nov 2007, 11:28 PM
I realise that I am not the only one on this thread but please my request for simple was a little tongue in cheek and although I know that a thorough understanding of any subject does require some technical jargon, surely to qualify this with a simplistc explanation would help myself and others to understand. After all I would presume that anyone who can understand what you're talking about with all those long and unfamilliar words would not need preaching to - it's us simple folk that need the preaching, but what is the use of preaching if we can't understand your language?

Denn (once again confused)

Denn, sorry if it was a bit "long winded".

Simply put, you can't use American standards in Australia (ANSI whatever) unless that standard has been selected for use by the Australian authorities.
You can earth your "metal welding work bench" in the following ways;

1] connect the work bench to the Main Earth Bar in your Distribution Board (breaker box) with a single insulated copper earth wire (green/yellow). The minimum size of this cable should be about 4 square millimetres. This is the preferred method.

2] with a copper cable of the same size & type as in 1] above, connect the work bench to a separate earth electrode (earth rod in the ground). If this method is used, it must be tested to ensure that it is ok. This method is not preferred.


Both of the above methods must be done by a licenced electrician.

dennford
10th Nov 2007, 11:40 PM
That is exactly what I needed to know. So by connecting to that earth bar any short should return to that earth ( is that right?). The way I see things at the moment is that in the first instance I have an earth on my welder, but should that fail for some reason then I have a backup earth going to my breaker box?

Denn

elkangorito
10th Nov 2007, 11:56 PM
That is exactly what I needed to know. So by connecting to that earth bar any short should return to that earth ( is that right?). The way I see things at the moment is that in the first instance I have an earth on my welder, but should that fail for some reason then I have a backup earth going to my breaker box?

Denn

This is not quite correct.

The earth that you put onto the work bench is purely an "equipotentential" earth. It can assist in helping circuit breakers to trip under a fault condition but it is not a Protective Earth. This means, you still must ensure that the earth in your welding units supply lead (a Protective earth) is intact & functional. It does not mean that you can get lazy about "earthing" (no offense intended).

Since we are talking about electricity & workshops, I am of the opinion that it would be a very good idea to ensure that all metallic workshop/shed fixtures (stationary) are equipotentially bonded. This also includes the physical structure of the workshop/shed if it is metallic. That is, an electrician can run earth cables to each of these fixtures & ensure that they are appropriately connected to the main earthing system. This will not require the installation of extra earth electrodes (rods in the ground).

BobL
11th Nov 2007, 12:09 AM
. . . . . .with a copper cable of the same size & type as in 1] above, connect the work bench to a separate earth electrode (earth rod in the ground). If this method is used, it must be tested to ensure that it is ok. This method is not preferred.

Both of the above methods must be done by a licenced electrician.

The loophole word his is "can", ie "You can earth your "metal welding work bench" in the following ways;"

Since it does not say you "must", and since a bench is not an electrical appliance, there is no law preventing anyone from running a cable between a work bench and a steel pipe driven into the ground. You also do not get it tested unless you are claiming it to be an earth. "Your Honour - it's an alternative to me wearing me foilie while I'm welding". It's cheap and simple to do and if I was welding every day I'd be doing it to my bench.

The legalities start when you start fiddling with the electrical appliances and their circuit.

dennford
11th Nov 2007, 12:17 AM
I shall be going to bed shortly but something to ask in the meantime, It would possibly help if I knew what you mean by equipotentially?

Denn

elkangorito
11th Nov 2007, 12:24 AM
The loophole word his is "can", ie "You can earth your "metal welding work bench" in the following ways;"

Since it does not say you "must", and since a bench is not an electrical appliance, there is no law preventing anyone from running a cable between a work bench and a steel pipe driven into the ground. You also do not get it tested unless you are claiming it to be an earth. "Your Honour - it's an alternative to me wearing me foilie while I'm welding". It's cheap and simple to do and if I was welding every day I'd be doing it to my bench.

The legalities start when you start fiddling with the electrical appliances and their circuit.

Unfortunately, "it" says that you "must" connect the device (in this case, a work bench) in accordance with the regs, "if" you are going to connect it at all. Unfortunately again, as soon as you add any kind of earth to an installation, you are in fact, adding to the whole electrical installation & as such, the addition must comply with the regs...especially earths.

If the "work bench" were only to be used for welding purposes & if the welding unit is a standard primary/secondary reactance transformer, I wouldn't bother earthing the bench at all. But since other devices that are not isolated from the main supply can be placed on such benches (240/415v), it's not a bad idea to include the bench in the "equipotential" bonded equipment list, which must be carried out by licenced persons & according to the regs.

elkangorito
11th Nov 2007, 12:29 AM
I shall be going to bed shortly but something to ask in the meantime, It would possibly help if I knew what you mean by equipotentially?

Denn

Potential means "voltage". "Equi" is short for "equivalent" or "same".

In short, "equal voltages" (preferably 0v).

ds2006
11th Nov 2007, 12:36 AM
Glad to see the use of earthing, grounding and bonding getting sorted out, as there certainly was some confusion in the earlier posts. The steel frame of my workshop is connected to the main earth bar via a short length of 4mm cable. All my metal benches are welded to the frame at some point and this is done purely for the reason that power tools are at some stage going to be used on them.

I was actually doing some work on my 3 phase mig on Thursday - replacing the power supply cable and installing a switch on the unit itself. The earth wire was holding on by a single strand to one of the old style washer retainers. A crimp on lug, condictive coated 10/32 earth screw and top lock nut soon fixed that problem.

elkangorito
11th Nov 2007, 12:39 AM
Glad to see the use of earthing, grounding and bonding getting sorted out, as there certainly was some confusion in the earlier posts. The steel frame of my workshop is connected to the main earth bar via a short length of 4mm cable. All my metal benches are welded to the frame at some point and this is done purely for the reason that power tools are at some stage going to be used on them.

I was actually doing some work on my 3 phase mig on Thursday - replacing the power supply cable and installing a switch on the unit itself. The earth wire was holding on by a single strand to one of the old style washer retainers. A crimp on lug, condictive coated 10/32 earth screw and top lock nut soon fixed that problem.

ds2006, it appears that you have successfully "equipotententially bonded" all of the equipment in your workshop.
As for the earth wire in your MIG, I think you have potentially saved your own life.:2tsup:

patty
11th Nov 2007, 12:50 AM
nah mate the crimp on a lug you are refering to is either A Stenko Lug or a Good ole Ross Courtney lug that was around for donkeys years but i bet elkangorito can tell ya a bit more history on it that is or sure by the lok of some of the blogs and that is no disrespect Elka

elkangorito
11th Nov 2007, 12:54 AM
nah mate the crimp on a lug you are refering to is either A Stenko Lug or a Good ole Ross Courtney lug that was around for donkeys years but i bet elkangorito can tell ya a bit more history on it that is or sure by the lok of some of the blogs and that is no disrespect Elka

Not quite right patty. I've never heard of a Stenko lug but I am familiar with the Ross Courtneys. To me, it doesn't matter what type of connection exists. The most important thing to realise is if the connection is good or bad.:U

PS. Since your a Newy guy, I was born & bred in Cessnock...now living in Thailand.

ds2006
11th Nov 2007, 01:01 AM
nah mate the crimp on a lug you are refering to is either A Stenko Lug or a Good ole Ross Courtney lug that was around for donkeys years but i bet elkangorito can tell ya a bit more history on it that is or sure by the lok of some of the blogs and that is no disrespect Elka

Crimp on lug was standard ring terminal for a #10 stud. What was there before I have no idea what it was called but I have never liked them. It was a copper washer with sides that run almost all around the circumference. You make a loop with the wire and then place ii in this washer and put a standard washer on top and screw it down. Idea is that all the wire is contained inside the washers.

I also use ferrules for any screw down connector where the screw bites directly into the wire (as in extension lead sockets and terminal connectors). Too easy to cut through the wire strands otherwise. Ferrules are cheap and quick and easy to install and save problems form arising down the track.

patty
11th Nov 2007, 01:06 AM
Hey ElKa..Screw the Spark talk it is always good to hear from a fellow Novocastrian! I am Serious so what gets ya ova dat way any way? besides the great surf?Take care!! Great to hear from someone ove dat wa makin it big i hope anyway cheers patty

BobL
11th Nov 2007, 01:41 AM
Unfortunately, "it" says that you "must" connect the device (in this case, a work bench) in accordance with the regs, "if" you are going to connect it at all. Unfortunately again, as soon as you add any kind of earth to an installation, you are in fact, adding to the whole electrical installation & as such, the addition must comply with the regs...especially earths.

I agree with you if it is being claimed as an official earth, but I disagree with you about the "any kind of earth" statement. At no stage am I calling it an earth, and I'm not relying on it as an earth and not suggesting at all that it is an alternative to proper earthing. It's a wire attached to a free standing bench connected to a metal spike in the ground.

If I connect a wire from say a sink, or a bird cage, a BBQ, or a bed, to a metal stake in the ground (ie its a potential earth), do I have to have it done by an electrician and tested? Does that mean all Hills hoists, ie wires attached to a metal stake in the ground have to be electrically tested? What about my grape vine and the metal wire running across the inside of my shed connected to the steel poles that make up the shed and run into the ground?

What if a bench is welded to the steel frame of a shed and one of the steel poles extends 4 ft into the soil - does that have to be installed and tested by a sparky? Nowhere in any of the AUS bulding regs does it say that all possible objects around a building that may potentially act as conductors to the ground have to be installed by licensed electricians and tested as earths. My reading of the codes are they would only have to be installed and tested as such if they are connected to the official building earth circuit and/or claimed as an official earth and they are being relied on as a safety device.

elkangorito
11th Nov 2007, 01:57 AM
Hey ElKa..Screw the Spark talk it is always good to hear from a fellow Novocastrian! I am Serious so what gets ya ova dat way any way? besides the great surf?Take care!! Great to hear from someone ove dat wa makin it big i hope anyway cheers patty

I know this is :offtopic: & therefore will only say this once.

I came to Thailand because basically, I was sick of the western way of life (working yourself to death & the zillions of rules & regs).

I teach English at a technical college but soon hope to start an engineering/electrical business. Unfortunately, I'm not "makin it big" here but that is part of the joy of living in Thailand. The people here have a totally different outlook on life. Number 1 is "fun". If you are not having fun, no matter where you are in Thailand, you don't belong here. For the first time in my life, I wake up every morning with a smile on my face & come home the same way. I am in no way "stressed" at work although I do miss the "challenges" of the western working life from time to time.

Anyway mate, you bloodywell misbehave...& have fun.:bgth:

elkangorito
11th Nov 2007, 02:24 AM
Bob, my comments in blue.


I agree with you if it is being claimed as an official earth, but I disagree with you about the "any kind of earth" statement. At no stage am I calling it an earth, and I'm not relying on it as an earth and not suggesting at all that it is an alternative to proper earthing. It's a wire attached to a free standing bench connected to a metal spike in the ground...

and as such, it will then form a part of the earthing system, which MUST comply with the regs & MUST be installed by a licenced electrician. Your idea of what constitutes an "earth" may be quite different to the technical meaning. This is why the regs are here.

If I connect a wire from say a sink, or a bird cage, a BBQ, or a bed, to a metal stake in the ground (ie its a potential earth), do I have to have it done by an electrician and tested? Does that mean all Hills hoists, ie wires attached to a metal stake in the ground have to be electrically tested? What about my grape vine and the metal wire running across the inside of my shed connected to the steel poles that make up the shed and run into the ground?

Forgiving your over-reaction, the earthing of such things is ludicrous & would serve no purpose in the role of establishing an approved earthing system. This is the reason why such things are precluded from the regs. Earthing is all about the risk of "indirect" shock from applicable equipment. Items such as clothes lines, sinks, bird cages & the like are obviously not applicable.

What if a bench is welded to the steel frame of a shed and one of the steel poles extends 4 ft into the soil - does that have to be installed and tested by a sparky? Nowhere in any of the AUS bulding regs does it say that all possible objects around a building that may potentially act as conductors to the ground have to be installed by licensed electricians and tested as earths. My reading of the codes are they would only have to be installed and tested as such if they are connected to the official building earth circuit and/or claimed as an official earth and they are being relied on as a safety device.

You are correct in saying this BUT IF you do decide to include anything with the earthing system, it MUST comply with the regs & be done by a licenced electrician.



See the 1st paragraph of this post;
http://www.woodworkforums.ubeaut.com.au/showpost.php?p=622805&postcount=35

Also, the below links may be of some use;

http://www.austlii.edu.au/au/legis/nsw/consol_act/esa2004309.txt

http://www.austlii.edu.au/au/legis/nsw/consol_act/hba1989128.txt


Also, I'm happy to clarify your queries with reference to the Australian Wiring Rules but I can assure you that others may not appreciate the detail & length of such a discussion.

dennford
11th Nov 2007, 08:33 AM
I think that I am getting a somewhat hazy idea of the subjectand from my understanding believe that my system is okay, you may tell me different.


All structural parts of my shed, including benches are earthed to the breaker box

I run a table saw which stands isolated from any structural entity but is earthed via the power lead.

Most of my welding is done outside the main shed in a lean to where I have a solid steel bench that is aalso isolated from the shed structure.

So I now presume that when welding this bench will become part of the circuit and not having any other circuit liable to interfere should be okay?

However what I would ask is how about when I am using an angle grinder in this area - I have now introduced a potential foriegn circuit?

Denn

BobL
11th Nov 2007, 10:39 AM
RE: Forgiving your over-reaction, the earthing of such things is ludicrous & would serve no purpose in the role of establishing an approved earthing system. This is the reason why such things are precluded from the regs. Earthing is all about the risk of "indirect" shock from applicable equipment. Items such as clothes lines, sinks, bird cages & the like are obviously not applicable.

Well that's exactly my point. :-) Just because a cable is connected doesn't imply that its an earth.

I called one of my relatives who is a senior OHS person for the state electrical company and asked his how my idea of not calling it an earth would stack up in an inspection. Basically its one of primary purpose and intent. If it walks and quacks like a duck it will be treated like a duck - so the obvious wire connected to the work bench and stake in the ground will be seen as an earth and treated as such no matter what it is called and paperwork could be called for. The bench welded to the steel frame of a shed with the frame extending into the ground won't unless it is specifically documented as such.

Dennford raises a good point. If you have a metal bench outside on the ground then the bench is already partially grounded? Does a sparky have to be called in to check how good the grounding is?

elkangorito
12th Nov 2007, 04:24 AM
My comments in blue.


I think that I am getting a somewhat hazy idea of the subjectand from my understanding believe that my system is okay, you may tell me different.
Your system sounds perfectly ok.

All structural parts of my shed, including benches are earthed to the breaker box
This is the only way permitted by the Wiring Rules, to do this.

I run a table saw which stands isolated from any structural entity but is earthed via the power lead.
Yes, it is earthed via the earth cable in the power lead.

Most of my welding is done outside the main shed in a lean to where I have a solid steel bench that is aalso isolated from the shed structure.

So I now presume that when welding this bench will become part of the circuit and not having any other circuit liable to interfere should be okay?
There is no requirement in ASNZS 3000:2000 to earth this bench. BUT, if you wish to do this, it must be done in the same way as all of the other things you have earthed i.e. an earth cable back to the breaker box. Again, this is "electrical work" & as such, must be carried out by a licenced electrician.

However what I would ask is how about when I am using an angle grinder in this area - I have now introduced a potential foriegn circuit?
Yes you have "introduced a potentially foreign circuit", but that doesn't mean that you must earth your bench.

Dennford, what you have sounds perfectly acceptable & in accordance with the Wiring Rules. Well done.:2tsup:

Denn


RE: Forgiving your over-reaction, the earthing of such things is ludicrous & would serve no purpose in the role of establishing an approved earthing system. This is the reason why such things are precluded from the regs. Earthing is all about the risk of "indirect" shock from applicable equipment. Items such as clothes lines, sinks, bird cages & the like are obviously not applicable.

Well that's exactly my point. :-) Just because a cable is connected doesn't imply that its an earth.

I called one of my relatives who is a senior OHS person for the state electrical company and asked his how my idea of not calling it an earth would stack up in an inspection. Basically its one of primary purpose and intent. If it walks and quacks like a duck it will be treated like a duck - so the obvious wire connected to the work bench and stake in the ground will be seen as an earth and treated as such no matter what it is called and paperwork could be called for. The bench welded to the steel frame of a shed with the frame extending into the ground won't unless it is specifically documented as such.

Dennford raises a good point. If you have a metal bench outside on the ground then the bench is already partially grounded? Does a sparky have to be called in to check how good the grounding is?

Bob, you quoted from post #40, "At no stage am I calling it an earth, and I'm not relying on it as an earth and not suggesting at all that it is an alternative to proper earthing. It's a wire attached to a free standing bench connected to a metal spike in the ground."

Could you kindly tell me what this is, its' purpose & how it is supposed to function?
If you want to muck around with electricity, be it on your own head. There is only one correct, legal & EFFECTIVE way to earth "extraneous conductive parts" (metallic benches etc) & it is NOT how you would do it (with spikes etc).

dennford
12th Nov 2007, 08:40 AM
Thanks once again, it looks as though your persistance is getting places.

Denn

BobL
12th Nov 2007, 09:34 AM
Could you kindly tell me what this is, its' purpose & how it is supposed to function?

Lets say you have an live angle grinder sitting on your metal bench and a bit of steel falls across the cable exposing it and making the table live. If the table is not grounded the table can sit their live - someone touches it and they're in trouble. If the table is grounded the breakers will trip and problem can be fixed. I agree the best way to earth the bench is to the electrical system but that legally requires getting a sparky in whereas I though my idea wouldn't. I also already agreed in my previous post that legally all earthing must be done by a sparky - I have no argument there.

If you want to muck around with electricity, be it on your own head. There is only one correct, legal & EFFECTIVE way to earth "extraneous conductive parts" (metallic benches etc) & it is NOT how you would do it (with spikes etc).

FWIW I've been working and trouble shooting in labs that use up to 20,000 V, and teaching university level electromagnetism for 30 years. I am very familiar with earthing principles having dealt with a series of persistent ground loop problems in the labs I work in. When the sparkies couldn't fix it I organised them to install a series of 1" thick copper earth straps running around our labs that were connected to a big copper mains water junction underground outside our lab ie a big spike in the ground. Since then we have had absolutely no problems. When sparkies come to our labs to fix something I often have to work with them because they don't always understand what's involved. I pay close attention to regulations because of OHS and legal ramficiations but the regulations are sometimes not the only way to do things effectively and do not cover all aspects of safety especially in our special laboratories.

dennford
12th Nov 2007, 12:03 PM
Lets say you have an live angle grinder sitting on your metal bench and a bit of steel falls across the cable exposing it and making the table live. If the table is not grounded the table can sit their live - someone touches it and they're in trouble. If the table is grounded the breakers will trip and problem can be fixed. I agree the best way to earth the bench is to the electrical system but that legally requires getting a sparky in whereas I though my idea wouldn't. I also already agreed in my previous post that legally all earthing must be done by a sparky - I have no argument there.



In the above situation I am presuming that although I can't legally attach the bench to the earth on the electrical system, surely I can bolt that same bench to the shed structure or extend an existing bench; both of which are allready earthed - that seems to me to be an obvious way around the legalities. but would that introduce further complications? (apart from the obvious one of making sure that any such connections were secure and as close to the point where the shed is grounded as possible).

Denn

BobL
12th Nov 2007, 12:53 PM
In the above situation I am presuming that although I can't legally attach the bench to the earth on the electrical system, surely I can bolt that same bench to the shed structure or extend an existing bench; both of which are allready earthed - that seems to me to be an obvious way around the legalities. but would that introduce further complications? (apart from the obvious one of making sure that any such connections were secure and as close to the point where the shed is grounded as possible).

Denn

The official or legal line is you should leave it all to the sparky.

In practice my sources tell me this;
- that if anything looks like an earth (ie a cable or a metal bar that connects a bench to a spike in the ground, or another device connected to an approved earth ) you should get it tested and signed off by a sparky. If you modify or expand an existing bench attached to an officially approved earth you should also get that tested. If anything goes wrong and there's no approved paperwork, court appearances and fines could result.

- if your shed has steel poles and they happen to run into the ground (and provide an effective ground) and you weld your bench to those poles primarily for support and not for electrical safety purposes then no approval is required. The primary purpose of the welded connection is support and the fact that it provides some form of earthing is incidental. If it's a workplace and something goes pear shaped and you end up in court you might still be held liable for not providing an adequate earthing of a work environment but you are unlikley to be liable for installing an unapproved earth.

This situation clearly demonstrates how, no matter how detailed regulations are they can't cover every situation. I've seen attempts to write regulations that try to do that and it is impossible. Deep fundamental knowledge of a physical phenomenon will always save more lives than regulations. Unfortunately few people have that depth of understanding which is why regulations are very useful for these people and especially to cover their behinds in court.

elkangorito
12th Nov 2007, 07:41 PM
In the above situation I am presuming that although I can't legally attach the bench to the earth on the electrical system, surely I can bolt that same bench to the shed structure or extend an existing bench; both of which are allready earthed - that seems to me to be an obvious way around the legalities. but would that introduce further complications? (apart from the obvious one of making sure that any such connections were secure and as close to the point where the shed is grounded as possible).

Denn

I don't see any real problem with your idea. The primary thing to remember with all earthing is that the impedance (resistance) from the earthed equipment back to earthing electrode is within accepted tolerances, according to the type of protective devices used. The secondary thing to remember is that an effective earthing system will not permit dangerous voltages to be present on any conductive parts, for longer than the required times. A dangerous voltage is considered to be;

1] above 50v R.M.S. (AC) and;
2] above 120v "ripple free" D.C.

Generally, a protective device (circuit breaker, fuse) must clear a fault within 0.4 seconds. Longer time periods can apply for other types of circuits. Of course, the best way to protect yourself is to use an RCD (20mS at 30mA), which should be tested monthly by pressing the "press to test" button.