george t. everett
Senior Member
- Location
- New York
Is it permissible to ground a metal switch box by useing the clamp screw, without the clamp, or do I have to use a green grounding screw ?
Grding metal switch boxes
- Thread starter george t. everett
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electricman2
Senior Member
- Location
- North Carolina
- Occupation
- Retired Electrical Contractor
Re: Grding metal switch boxes
Not according to 250.148(A). Most clamp screws I've seen do not have large enough heads to properly secure a conductor anyway.
Not according to 250.148(A). Most clamp screws I've seen do not have large enough heads to properly secure a conductor anyway.
- Location
- Illinois
- Occupation
- retired electrician
Re: Grding metal switch boxes
I see no problem using the 10-32 clamp screw to bond the box as long as the clamp itself has been removed.
Don
I see no problem using the 10-32 clamp screw to bond the box as long as the clamp itself has been removed.
Don
Re: Grding metal switch boxes
I agree, thats what I have been trying to say all along, and wouldn't it be much better to use a green ground screw w/pigtail, g-clip, or green ground screw, it may keep you from getting a red tag, taking a chance on somthing as simple as that is IMO not worth the trouble. Most inspectors I deal with need to see a green ground screw or they will give a red tag. But then everybody on this forum says any screw, with the exception of a sheetmetal screw, will do as a ground screw.
pierre
Senior Member
- Location
- Westchester County, New York
Re: Grding metal switch boxes
The requirement for a green hex head screw is for devices, not in boxes. It certainly does not hurt to use the green hexhead screw, but it is not required.
The only real difference between the screw that holds the clamp in and the hexhead is color and the head is a little larger with serrations. I firmly believe the clamp screw will perform just fine. There are bigger fish to fry
The stranded pigtail with the stakeon fitting is a nice way to go, easy and fast.
Pierre
The requirement for a green hex head screw is for devices, not in boxes. It certainly does not hurt to use the green hexhead screw, but it is not required.
The only real difference between the screw that holds the clamp in and the hexhead is color and the head is a little larger with serrations. I firmly believe the clamp screw will perform just fine. There are bigger fish to fry
The stranded pigtail with the stakeon fitting is a nice way to go, easy and fast.
Pierre
electricman2
Senior Member
- Location
- North Carolina
- Occupation
- Retired Electrical Contractor
Re: Grding metal switch boxes
Pierre
Pierre
Not familiar with this, do you have a manufacturer and/or cat. no?
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Grding metal switch boxes
I make mine with 12 AWG stranded and a non insulated fork connector.
Ideal sells the premade green pig tails in a varity of configurations.
I make mine with 12 AWG stranded and a non insulated fork connector.
Ideal sells the premade green pig tails in a varity of configurations.
electricmanscott
Senior Member
- Location
- Boston, MA
- Occupation
- Massachusetts Master Electrician, one man show.
Re: Grding metal switch boxes
The clamp screw works as well as the hex screw if the clamp is removed and you wrap the wire around it properly . It is perfectly legal unless your boxes come with sheet metal screws for the clamps. Can anyone point out anything that says it has to be green? :roll:
[ November 15, 2003, 07:28 AM: Message edited by: electricmanscott ]
The clamp screw works as well as the hex screw if the clamp is removed and you wrap the wire around it properly . It is perfectly legal unless your boxes come with sheet metal screws for the clamps. Can anyone point out anything that says it has to be green? :roll:
[ November 15, 2003, 07:28 AM: Message edited by: electricmanscott ]
pierre
Senior Member
- Location
- Westchester County, New York
Re: Grding metal switch boxes
Electricman2
Ideal makes them, and you can find them on their website.
Pierre
Electricman2
Ideal makes them, and you can find them on their website.
Pierre
- Location
- Massachusetts
Re: Grding metal switch boxes
The question of if a grounding screw needs to green seems to come up a lot.
I have been on jobs and been told that also.
Why?
But in the case of grounding a box how would a green screw do anything to improve safety?
The question of if a grounding screw needs to green seems to come up a lot.
I have been on jobs and been told that also.
Why?
But in the case of grounding a box how would a green screw do anything to improve safety?
tonyi
Senior Member
Re: Grding metal switch boxes
The only thing I can think of is if conductor colors have been redesignated. Maybe you have a load of say 12-3 AC you wanted to use up and were going to use the red as a gnd wire where something called for an insulated gnd.
Should be pretty obvious though - if its under a box screw its the gnd. If the box is hot, then there's an issue
The only thing I can think of is if conductor colors have been redesignated. Maybe you have a load of say 12-3 AC you wanted to use up and were going to use the red as a gnd wire where something called for an insulated gnd.
Should be pretty obvious though - if its under a box screw its the gnd. If the box is hot, then there's an issue
tonyi
Senior Member
Re: Grding metal switch boxes
IMO its pretty bogus/sleazy/(add your own derisive adjectives here) . Essentially its using a NM connector to maintain gnd path integrity of the system - a purpose an ordinary NM connector was never designed to do or listed for.
If its that old cloth bound NM ("crumble wire") you have to treat it gently, and the gnds are undersized and need gentle treatment too to avoid breaking them. The NM clamp may have bunged them up a bit when it was torqued down.
I've seen this hack lots of times in older places...
IMO its pretty bogus/sleazy/(add your own derisive adjectives here) . Essentially its using a NM connector to maintain gnd path integrity of the system - a purpose an ordinary NM connector was never designed to do or listed for.
If its that old cloth bound NM ("crumble wire") you have to treat it gently, and the gnds are undersized and need gentle treatment too to avoid breaking them. The NM clamp may have bunged them up a bit when it was torqued down.
Re: Grding metal switch boxes
I'll give my age away here, but when I was first apprenticed, the old guy who was assigned to "show em the ropes", showed me how to wrap the wire around the Romex like that. He maintained the grounding connection was just as good, if not better, than using the clamp screw! (there were no threaded holes for a 10-32) Those days are long gone, now. The reasoning behind not allowing the clamp screw to be used is, IMO, because it may become loose, or it may not be tightened enough. It has been only recently (30 years or so) that grounding has become the standard. I recall when GFCIs first made their appearance. Nobody wanted to use them because of all the nuisance tripping. It turned out that everybody had defective and dangerous equipment, and the GFCIs were saving lives. Go figure.
I'll give my age away here, but when I was first apprenticed, the old guy who was assigned to "show em the ropes", showed me how to wrap the wire around the Romex like that. He maintained the grounding connection was just as good, if not better, than using the clamp screw! (there were no threaded holes for a 10-32) Those days are long gone, now. The reasoning behind not allowing the clamp screw to be used is, IMO, because it may become loose, or it may not be tightened enough. It has been only recently (30 years or so) that grounding has become the standard. I recall when GFCIs first made their appearance. Nobody wanted to use them because of all the nuisance tripping. It turned out that everybody had defective and dangerous equipment, and the GFCIs were saving lives. Go figure.
- Location
- Massachusetts
Re: Grding metal switch boxes
I agree with you that is hack now but that was how trade schools where teaching how to do it.
tonyi
Senior Member
Re: Grding metal switch boxes
It was one less wire nut and gnd screw per box. Most j-boxes of era weren't pretapped for a 10-32, and would need to be tapped. Gnd clips hadn't shown up yet at that point. Less box fill - smaller boxes.
cheap/fast, cheap/fast yea, that's the ticket
I suppose there was a "comfort factor" for people familiar with AC as well. Wrapping bond wires around armor had been (still is) common practice. Although a lot of people still don't really understand how that bond wire really works...
It was one less wire nut and gnd screw per box. Most j-boxes of era weren't pretapped for a 10-32, and would need to be tapped. Gnd clips hadn't shown up yet at that point. Less box fill - smaller boxes.
cheap/fast, cheap/fast yea, that's the ticket
I suppose there was a "comfort factor" for people familiar with AC as well. Wrapping bond wires around armor had been (still is) common practice. Although a lot of people still don't really understand how that bond wire really works...
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