kmccormick
Member
Does the NEC limit or prohibit the use of sheet metal screws in raceways, wireway and cabinets etc... If so can you provide the Article(s)
Use of sheet metal screws
- Thread starter kmccormick
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flightline
Senior Member
Re: Use of sheet metal screws
Others here might disagree with me, but in the instance, lets say, of a new home, if the contractor has lost the screws to a panel cover, I have cited them for installing sheet metal screws in their place. I cite that this is not how the panel was listed; they have changed it.
In my time in the field, I have seen cables become shorted, either when installed, or over time, the pointed tip on a sheet metal screw has compromised the insulation on a conductor. Nowhere is this more spectacular than the situation where the main is on the opposite end of the panel, and the screw pokes through a yet unprotected service entrance conductor as it loops through the panel.
It is my assumption that manufacturers of electrical equipment take care when designing their equipment to choose fasteners of the proper size, length and overall design so as to provide a consistently safe product when installed properly. When someone is buying a new home or other such building, they should get the product they pay for, as it was designed, and as it was listed.
Others here might disagree with me, but in the instance, lets say, of a new home, if the contractor has lost the screws to a panel cover, I have cited them for installing sheet metal screws in their place. I cite that this is not how the panel was listed; they have changed it.
In my time in the field, I have seen cables become shorted, either when installed, or over time, the pointed tip on a sheet metal screw has compromised the insulation on a conductor. Nowhere is this more spectacular than the situation where the main is on the opposite end of the panel, and the screw pokes through a yet unprotected service entrance conductor as it loops through the panel.
It is my assumption that manufacturers of electrical equipment take care when designing their equipment to choose fasteners of the proper size, length and overall design so as to provide a consistently safe product when installed properly. When someone is buying a new home or other such building, they should get the product they pay for, as it was designed, and as it was listed.
G
Guest
Guest
Re: Use of sheet metal screws
I T-boned a panel screw into an ungrounded conductor once (a large one) and the load-center went ka-boom!
It was not a pointy screw, but the previous technicians had ground the screw through the insulation. It was an accident waiting to happen. After that I was even more cautious about conductor routing in panels, boxes, etc.
I T-boned a panel screw into an ungrounded conductor once (a large one) and the load-center went ka-boom!
It was not a pointy screw, but the previous technicians had ground the screw through the insulation. It was an accident waiting to happen. After that I was even more cautious about conductor routing in panels, boxes, etc.
Re: Use of sheet metal screws
I also T-boned the service conductor with a cover screw once. Mine only went ZZZZZZTTT. I backed the screws off, taped the damaged conductor, and wiped my brow. Whew! Once is all it takes to remind one to always check the location of the wires prior to screwing the cover back on.
Earl
PS, I know the wire was damaged, and needed to be replaced, but that had to wait until the meter could be pulled.
I also T-boned the service conductor with a cover screw once. Mine only went ZZZZZZTTT. I backed the screws off, taped the damaged conductor, and wiped my brow. Whew! Once is all it takes to remind one to always check the location of the wires prior to screwing the cover back on.
Earl
PS, I know the wire was damaged, and needed to be replaced, but that had to wait until the meter could be pulled.
kmccormick
Member
Re: Use of sheet metal screws
Thanks Guys.
We manufacture Kitchen equipment and I a trying to eliminate the use of sheet metal screws anywhere wire is present. It is a tough sell. This will help. I will also site codes related to cables and conductors through wood etc... which requires 1-1/4" space which we rarely have.
Thanks again.
Thanks Guys.
We manufacture Kitchen equipment and I a trying to eliminate the use of sheet metal screws anywhere wire is present. It is a tough sell. This will help. I will also site codes related to cables and conductors through wood etc... which requires 1-1/4" space which we rarely have.
Thanks again.
renosteinke
Senior Member
- Location
- NE Arkansas
Re: Use of sheet metal screws
KC- You'll best be served if you obtain the UL standard that most closely describes your product. Typically, the standards start off requiring mechanical protection for the wires; assorted tests often will highlight areas that need improvement.
KC- You'll best be served if you obtain the UL standard that most closely describes your product. Typically, the standards start off requiring mechanical protection for the wires; assorted tests often will highlight areas that need improvement.
electricmanscott
Senior Member
- Location
- Boston, MA
Re: Use of sheet metal screws
Flightline you are correct. I disagree with you. Talk about going overboard. :roll: Geez. What you described can happen with any type of screw in that situation.
Flightline you are correct. I disagree with you. Talk about going overboard. :roll: Geez. What you described can happen with any type of screw in that situation.
big john
Senior Member
- Location
- Portland, ME
Re: Use of sheet metal screws
I know of an incident where a mechanic went to do some work in a trough that housed the 480 feeders for an elevator machine room; the previous sparky hadn't been as careful as they should've been when forming the cables in the trough, and when the trough cover was installed, one of the screws went into one of the feeders. The installer was really lucky - there wasn't a short. The guy who went to service the installation wasn't nearly as lucky: He went to back out the screw and that little bit of movement was enough to cause a short. The resulting explosion gave him third-degree burns on his face and chest and he permanently lost the use of most of his fingers; there was a soft-ball sized hole in the steel trough cover.
Needless to say, one of the things I do religiously when making up any box, is to make sure there are no conductors in the paths of any of the cover-screws.
-John
I know of an incident where a mechanic went to do some work in a trough that housed the 480 feeders for an elevator machine room; the previous sparky hadn't been as careful as they should've been when forming the cables in the trough, and when the trough cover was installed, one of the screws went into one of the feeders. The installer was really lucky - there wasn't a short. The guy who went to service the installation wasn't nearly as lucky: He went to back out the screw and that little bit of movement was enough to cause a short. The resulting explosion gave him third-degree burns on his face and chest and he permanently lost the use of most of his fingers; there was a soft-ball sized hole in the steel trough cover.
Needless to say, one of the things I do religiously when making up any box, is to make sure there are no conductors in the paths of any of the cover-screws.
-John
G
Guest
Guest
Re: Use of sheet metal screws
Plastic or metal corner gussets integrated into the panel construction would be a good safety feature to prevent conductors from creeping into the corners where the screws always live. A gusset would make it physically impossible to create a screw penetration hazard.
A
a.wayne3@verizon.net
Guest
Re: Use of sheet metal screws
I previously posted a thread (1/4 in. set back for residential panels) This came about from contractors using sheet metal screws to mount a panel cover.The AHJ cited us for 1/4 in set back of cabinet on final.As it turned out it was done to stop the use of long sheet metal screws when panel cover screws were lost and long screws were installed .The AHJ cited that manufacturers screws were to be installed.
I previously posted a thread (1/4 in. set back for residential panels) This came about from contractors using sheet metal screws to mount a panel cover.The AHJ cited us for 1/4 in set back of cabinet on final.As it turned out it was done to stop the use of long sheet metal screws when panel cover screws were lost and long screws were installed .The AHJ cited that manufacturers screws were to be installed.
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