Wrong to use screw threads as a ground?

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jap said:
Bonding would not have prevented the shock in the scenario he's describing.
Bonding is what caused the gutter and all the other parts to become energized.

The maintenance man became parallel with the neutral return path.

Nothing would have prevented this shock short of removing the neutral return current prior to him touching the energized parts.

JAP>
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You are correct. I was just thinking about that.

There really is no way to prevent the shock hazard from an open neutral if you are touching any part of the electrical system or conductive item that is connected to the electrical system and the "earth, other than killing the power source.
 
It leads me to believe that the Grounded and EGC were together somewhere beyond the Service disconnect.

Otherwise (Unless the Neutral conductor that was taken loose was touching something metal at the service point) everything would have simply quit, but it would not have energized the gutter and the rest of the non current carrying parts.


JAP>
 
jap said:
Bonding would not have prevented the shock in the scenario he's describing.
Bonding is what caused the gutter and all the other parts to become energized.
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That is still no excuse for violating the code or making crappy connections just to preserve some paint.
 
iwire said:
That is still no excuse for violating the code or making crappy connections just to preserve some paint.
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I dont see a threaded connection that captures the required amount of threads a violation of the code.
As far as crappy connections, beauty is in the eye of the beholder.
I remember sometime back someone posted a picture of the way they terminated stranded wire to a receptacle and that was not the most wonderful connection I've ever seen but to each his own.
As far as preserving paint, I see it as preventing rust.

Oh well, after thinking about it all , there's reallly not that many times one has to fiel add lugs anyway. Generally there is enough opening in what is provided to do the trick.


JAP>
 
jap said:
I'll continue to not grind paint until someone tells me I have to.
I'll probably start grinding paint about the time I start using a torch to torch holes in Hoffman boxes and welding them to the beams.
Factory finishes deteriorate quickly once you start grinding the paint off.


JAP>
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Someone may not have told you to, but 250.12 says "Nonconductive coatings (such as paint, lacquer and enamel) on equipment to be grounded shall be removed from threads and other contact surfaces to ensure good electrical continuity...."
 
jap said:
I dont see a threaded connection that captures the required amount of threads a violation of the code.
As far as crappy connections, beauty is in the eye of the beholder.
I remember sometime back someone posted a picture of the way they terminated stranded wire to a receptacle and that was not the most wonderful connection I've ever seen but to each his own.
As far as preserving paint, I see it as preventing rust.

Oh well, after thinking about it all , there's reallly not that many times one has to fiel add lugs anyway. Generally there is enough opening in what is provided to do the trick.


JAP>
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Unless the screw holds something a screw threaded into an enclosure serves no usefull purpose. As such a screw when used to hold a terminal or conductor firmly againt a surface that is fr3 of paint and any other nonconductive coating does not rely on the threads of the fastener to make an electrical contact. The purpose of a properly threaded hole is the allow the fastener to be tightened with sufficient torque without stripping in order at pull the item to be grounded or connected firmly againt the surface of which the screw is fastening to.
I find tnat the topic of relying on the threads of a screw to make a connection to be somewhat misleading.
 
cowboyjwc said:
Someone may not have told you to, but 250.12 says "Nonconductive coatings (such as paint, lacquer and enamel) on equipment to be grounded shall be removed from threads and other contact surfaces to ensure good electrical continuity...."
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Well then, tell me how you grind the threads in the hole behind the neutral bar clean before you put the bonding screw in that you seem to grind the paint off of before installing it which I doubt you do.

JAP>
 
Ideally the enclosure is painted before the hole was drilled.
But if not, a thread firming screw will cut through any paint on the inside of the hole.
 
GoldDigger said:
Ideally the enclosure is painted before the hole was drilled.
But if not, a thread firming screw will cut through any paint on the inside of the hole.
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Which is what you commonly find with the neutral assembly bonding screw in small panelboards. They don't tap the hole, they do use a screw that will cut it's own threads, and will cut through the paint. This is also something tested and listed and is fine if installed per it's instructions, field made holes and accessories for such a purpose may not be.
 
kwired said:
Which is what you commonly find with the neutral assembly bonding screw in small panelboards. They don't tap the hole, they do use a screw that will cut it's own threads, and will cut through the paint. This is also something tested and listed and is fine if installed per it's instructions, field made holes and accessories for such a purpose may not be.
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Exactly, so if the bonding screw is good enough to cut through the paint and make a good electrical connection between the back side of the screw head and the surface it's tightening down against, I don't see why the same wouldn't hold true for a field installed ground bar, or bonding jumper or other instances that uses the exact same method.

JAP>
 
templdl said:
Unless the screw holds something a screw threaded into an enclosure serves no usefull purpose. As such a screw when used to hold a terminal or conductor firmly againt a surface that is fr3 of paint and any other nonconductive coating does not rely on the threads of the fastener to make an electrical contact. The purpose of a properly threaded hole is the allow the fastener to be tightened with sufficient torque without stripping in order at pull the item to be grounded or connected firmly againt the surface of which the screw is fastening to.
I find tnat the topic of relying on the threads of a screw to make a connection to be somewhat misleading.
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I disagree.
Some bonding screws go through the Neutral bar and thread into the hole behind it to make the electrical connection.
The underside of the head of the screw tightens down on the face of the neutral bar and serves a very useful purpose, yet the paint is not ground off the full length behind the neutral bar.

JAP>
 
jap said:
Exactly, so if the bonding screw is good enough to cut through the paint and make a good electrical connection between the back side of the screw head and the surface it's tightening down against, I don't see why the same wouldn't hold true for a field installed ground bar, or bonding jumper or other instances that uses the exact same method.

JAP>
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I agree with you, but also realize field installed components are often not tested and listed - other then say an equipment ground bar designed to fit a pre-drilled spot in the cabinet or something similar. I don't scrape paint for items that have specific instructions and are installed with specific hardware in a spot designed for installing that item. I sometimes get comments about scraping paint from inspetors in that situation and explain to them it was tested/listed/designed to go the way it is, and they usually let it go. Other field installed items at my own choice for location/device - I am likely removing paint.
 
kwired said:
I agree with you, but also realize field installed components are often not tested and listed - other then say an equipment ground bar designed to fit a pre-drilled spot in the cabinet or something similar. I don't scrape paint for items that have specific instructions and are installed with specific hardware in a spot designed for installing that item. I sometimes get comments about scraping paint from inspetors in that situation and explain to them it was tested/listed/designed to go the way it is, and they usually let it go. Other field installed items at my own choice for location/device - I am likely removing paint.
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I agree. If the UL listing allows for the it to be assembled in that manor then it would be allowed. Cleaning the surfaces to be joined I agree would still be a good practice.
 
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