Building Steel Shocking

[ramurray]

I have a subcontractor that is complaining of getting shocked when working
with plumbing pipe that is touching building steel.

Our temporary power is not connected to building steel for grounding purposes.

However, the welding that is going on is all over the structure. Most of the building steel

is installed and connected. The welders use the building steel as a connection due to the

installation.

How far from a welder can someone feel a tingle or a shock if they touch another metal piece such as cable tray or

EMT while also in connection with the building steel?

 

[Strathead]

I have a subcontractor that is complaining of getting shocked when working
with plumbing pipe that is touching building steel.

Our temporary power is not connected to building steel for grounding purposes.

However, the welding that is going on is all over the structure. Most of the building steel

is installed and connected. The welders use the building steel as a connection due to the

installation.

How far from a welder can someone feel a tingle or a shock if they touch another metal piece such as cable tray or

EMT while also in connection with the building steel?

Rather than dwell on that question, I would approach this from a different angle. If the "tingle" is coming from electrical flow (as opposed to static electricity build up) You can measure it with a volt meter. Go from the steel to the plumbing pipe. I fail to see how you could have enough voltage to feel between the two. They should be electrically bonded all over the place.

 

[wirenut1980]

I have a subcontractor that is complaining of getting shocked when working
with plumbing pipe that is touching building steel.

Our temporary power is not connected to building steel for grounding purposes.

However, the welding that is going on is all over the structure. Most of the building steel

is installed and connected. The welders use the building steel as a connection due to the

installation.

How far from a welder can someone feel a tingle or a shock if they touch another metal piece such as cable tray or

EMT while also in connection with the building steel?

So, the welder is using building steel as the neutral? Oh boy...:happysad:

There is no specific distance that any of us can tell you. Just know that the return current will take all available paths back to the source. There could be current on anything grounded while the welding is going on.

 

[kwired]

I doubt it is the welder. If work lead is not well bonded or is relying on too small of a conductor at some time that point will overheat and fail. When this happens welder output will be open circuit and the welding crew will not be able to weld. There may be voltage problems when they are attempting to weld with the open circuit condition, but they will remedy the problem fairly quickly if they are not able to weld. Overheating of undesired current paths is biggest problem that may be encountered with allowing welding current to flow everywhere like they are doing.

You need to find out what else they are contacting that is giving the voltage potential. This building steel is likely earthed pretty well even if not connected to a grounding electrode conductor. My best guess is there is voltage on the equipment grounding system of the temporary power system you are using and you need to find out why and where the source is. They are probably in contact somehow with equipment grounding conductor from power tools or other equipment and then touch the metal structure.

May not even be anything wrong in the temporary power equipment you have provided - could be in the power system where that is fed from whether it is service fed or from another building or structure. Poor neutral connection or improper neutral to ground bonds ahead of this temporary power could result in this kind of problem. Could even be a POCO problem caused by bad neutral connection somewhere in their primary MGN conductor.

 

[iwire]

I have a subcontractor that is complaining of getting shocked when working
with plumbing pipe that is touching building steel.

Our temporary power is not connected to building steel for grounding purposes.

First off, if the temp power enters the building you must bond the steel.

A few years ago an EC did not bond the steel, a temp light branch circuit faulted to steel and energized the structure. Hospital trips for a couple of guys, big OSHA fines and that EC was thrown off that 950K electrcal job.

I would start with bonding the steel to the GEC of the supply.

 

[kwired]

First off, if the temp power enters the building you must bond the steel.

A few years ago an EC did not bond the steel, a temp light branch circuit faulted to steel and energized the structure. Hospital trips for a couple of guys, big OSHA fines and that EC was thrown off that 950K electrcal job.

I would start with bonding the steel to the GEC of the supply.

He might have situation where there was no structure when temp power was placed and what is there now is what was erected since then.

 

[Gac66610]

I have a subcontractor that is complaining of getting shocked when working
with plumbing pipe that is touching building steel.

Our temporary power is not connected to building steel for grounding purposes.

However, the welding that is going on is all over the structure. Most of the building steel

is installed and connected. The welders use the building steel as a connection due to the

installation.

How far from a welder can someone feel a tingle or a shock if they touch another metal piece such as cable tray or

EMT while also in connection with the building steel?

IMO .... the ground clamp from the welder should be placed as close as possible to the welding area, which i'm sure it is, the clamp may not be on well enough and the current from the welder is looking for other paths to follow

if it were me there, i would (politely as possible) ask to check their grounding clamps and wire,(or voice your concerns to the foreman) just to be sure nothing has come loose, or just a bad connection and your grounding path is better than theirs

 

[iwire]

IMO .... the ground clamp from the welder should be placed as close as possible to the welding area, which i'm sure it is,

Typically during building construction the ground clamps are landed at ground level near the welder and the electrode lead may be several hundred feet, this is not an issue (unless it is a machine) and not unsafe.

the clamp may not be on well enough and the current from the welder is looking for other paths to follow

There is no other possible path between the structure and the welder itself. The only path is through the grounding clamp. If it is loose they can't weld or the welds will be inconsistent.

if it were me there, i would (politely as possible) ask to check their grounding clamps and wire,(or voice your concerns to the foreman) just to be sure nothing has come loose, or just a bad connection and your grounding path is better than theirs

I am going to be very surprised if the welding process has anything to do with the shocks.

 

[iwire]

He might have situation where there was no structure when temp power was placed and what is there now is what was erected since then.

It is great when people explain the obvious.

Yeah, that is almost always the case and it certainly is a gray area when it is the time to bond the new structure. But IMO if it is enough of a structure that you are hanging temp lighting and or temp receptacles from it bonding it is both required and wise.

 

[kwired]

IMO .... the ground clamp from the welder should be placed as close as possible to the welding area, which i'm sure it is, the clamp may not be on well enough and the current from the welder is looking for other paths to follow

if it were me there, i would (politely as possible) ask to check their grounding clamps and wire,(or voice your concerns to the foreman) just to be sure nothing has come loose, or just a bad connection and your grounding path is better than theirs

If the work clamp has that poor of connection what is the chance they can successfully weld? I hope most welders are smart enough to look for the problem if they can't strike an arc and not just sit there hoping it will eventually start arcing. In doing so they will remove the electrode from the work and there will no longer be any potential to anything except the isolated electrode.

Even with good work clamp connection, current is going to take multiple paths if they exist.

Amount of current that takes a particular path depends on impedance of that path.

In order for you to feel a shock your body has to have a lower impedance than any other path between the points of potential, otherwise the current will be shunted and the potential between those two points will not exist or will be much lower.

 

[Strathead]

First off, if the temp power enters the building you must bond the steel.

A few years ago an EC did not bond the steel, a temp light branch circuit faulted to steel and energized the structure. Hospital trips for a couple of guys, big OSHA fines and that EC was thrown off that 950K electrcal job.

I would start with bonding the steel to the GEC of the supply.

Too stupidly step in between your feud with KWire, I have never really thought of bonding temp power to the building as it comes out of the ground, and I have never had one of my men bring it up, so, while I agree it should be obvious, I admit a shortfall in my intelligence on this matter, so I for one, am glad he pointed it out.

Secondly, why wouldn't you START with a voltage test to find out where the stray voltages are coming from? Even if they bonding "solves" this problem, the voltage potential is likely to be over 50 volts to cause a sensation and that is still a problem.

 

[kwired]

Secondly, why wouldn't you START with a voltage test to find out where the stray voltages are coming from? Even if they bonding "solves" this problem, the voltage potential is likely to be over 50 volts to cause a sensation and that is still a problem.

Exactly right. If people are getting shocked there is a stray voltage issue somewhere, bonding that steel will not stop any stray current - it just creates more low impedance paths. If one should open the path accidently somewhere the symptoms come back.

I still insist there is likely a bad neutral or improper neutral - ground bond someplace at or ahead of the temporary power. Bonding items in the area only mask the problem. Maybe I am wrong but think it needs verified before bonding items in the area and calling it good.

 

[iwire]

Too stupidly step in between your feud with KWire, I have never really thought of bonding temp power to the building as it comes out of the ground, and I have never had one of my men bring it up, so, while I agree it should be obvious, I admit a shortfall in my intelligence on this matter, so I for one, am glad he pointed it out.

Fair enough.

Secondly, why wouldn't you START with a voltage test to find out where the stray voltages are coming from? Even if they bonding "solves" this problem, the voltage potential is likely to be over 50 volts to cause a sensation and that is still a problem.

Me? If I was there I would quickly pin it down with some testing just as many would.

However, from my vantage point here, not seeing the site and perhaps my lack of writing skills I would find it virtually impossible to explain in a forum post exactly how to do this testing.

It is required to be bonded and I suspect if it is bonded the issue will show itself with a tripped breaker. If not I would look more into it.

 

[iwire]

I still insist there is likely a bad neutral or improper neutral - ground bond someplace at or ahead of the temporary power.

I am not saying you are wrong but I am not following you.

If the service is isolated from the building and the buildings plumbing I am not seeing how a open neutral would be producing a shock between the plumbing and building steel.

With an open service neutral I could see getting a shock between an EGC brought in from the service and the building steel and / or plumbing.

 

[kwired]

Fair enough.




Me? If I was there I would quickly pin it down with some testing just as many would.

However, from my vantage point here, not seeing the site and perhaps my lack of writing skills I would find it virtually impossible to explain in a forum post exactly how to do this testing.

It is required to be bonded and I suspect if it is bonded the issue will show itself with a tripped breaker. If not I would look more into it.

If it is stray current on the neutral/EGC there will be no breaker tripping - won't even be GFCI tripping for GFCI required circuits. It problem is far enough upstream it will still exist even when the feeder to the temporary power is turned off.

Like you said - if you were there you likely would find out what the problem is fairly quickly or at least know where to start looking for more issues, I likely would also, the OP maybe is not as good of a trouble shooter as you or I and we are not doing him any favors if we just tell him to bond the steel in question and not find out why there is voltage there in the first place.

 

[hillbilly1]

Usually what I do in this situation is start turning off breakers until the voltage disappears, then narrow it down from there. Probably a temp lighting circuit that is making contact with the building steel somwhere. I wired a gas station years ago where everybody was getting shocked off the steel door frames, when I turned off the panel feeding the gas pumps, the voltage disappeared. The contractor who wired the pumps did pull an EGC to the pumps, but was relying on the rigid conduit as the ground. The only problem with that though, was he used a PVC nipple between the pump wireway and the panel. He had a live spare 20 amp circuit in the wireway laying against the enclosure. Even with all of the buried rigid in the ground, the current flow was not enough to trip the breaker.

 

[copper chopper]

I am wondering if the building steel is properly grounded is there a ground ring in place , the only way i see poeple feeling a tingle in this sitiuation is that they are becoming a better ground than the one provided by the steel.
If everything is bonded as it should be this would not happen.

the only other issue I have seen is if these guys are working on lifts and from them driving even 20 feet this builds up static electricity in themselves and when they touch the building steel whamo- they get blasted.:thumbsup:

 

[kwired]

I am wondering if the building steel is properly grounded is there a ground ring in place , the only way i see poeple feeling a tingle in this sitiuation is that they are becoming a better ground than the one provided by the steel.
If everything is bonded as it should be this would not happen.

Depends on a few things - most of which I have touched on previously in this thread. If the steel structure is bolted to steel that is encased in concrete in the earth - they should have very little resistance to earth in most cases. If that is the case the steel structure is not the source of elevated voltage it is just a better contact surface that is grounded than dirt is. Something else has to be the source of voltage and people are in contact with that at same time they are touching the steel. In this case bonding the steel will probably have little if any effect in improving the problems.

Now if the steel for some reason is isolated from ground and is energized by something I think the problem would be a little more obvious, and bonding the steel will definately solve some problems or cause overcurrent devices to open. I don't think the chance of this is as great as the chance of the first scenario.

the only other issue I have seen is if these guys are working on lifts and from them driving even 20 feet this builds up static electricity in themselves and when they touch the building steel whamo- they get blasted.:thumbsup:

How often have you seen this? Most tires on equipment anymore are conductive enough that they bleed off any static electricity. Years ago when that was a bigger problem with machinery because the tires were composed of more rubber than they are today, they often had a metal chain that drug on the ground and served no purpose other than to discharge static electricity.

 

[DelightedInYahweh]

How often have you seen this? Most tires on equipment anymore are conductive enough that they bleed off any static electricity. Years ago when that was a bigger problem with machinery because the tires were composed of more rubber than they are today, they often had a metal chain that drug on the ground and served no purpose other than to discharge static electricity.

We get popped pretty often when we are driving the scissor lifts around putting in the interior lighting in the showrooms and pulling the conductors in. Especially when we have long rows of fluorescents and the carpet is in. Nothing like zooming down a row to pull in the circuit and then PATOW!!!! one good pop on the side of the neck from one of the hanging fluorescent wires!!! It sure makes your toes curl :jawdrop:

 

[kwired]

We get popped pretty often when we are driving the scissor lifts around putting in the interior lighting in the showrooms and pulling the conductors in. Especially when we have long rows of fluorescents and the carpet is in. Nothing like zooming down a row to pull in the circuit and then PATOW!!!! one good pop on the side of the neck from one of the hanging fluorescent wires!!! It sure makes your toes curl :jawdrop:

If carpet is already in that is pretty understandable that would happen. You could have a ground wire attached to your lift - but then you have something dragging with you, getting caught on other objects, getting caught up in the lift itself, etc.

You could also have a jumper at the lift platform that you bond to structural items every time you move if this is going to be a big enough problem. You will learn to remember to bond when you get zapped a time or two.