Does grounding for four receptacles pigtail have to be a green screw?

Status
Not open for further replies.

Eddy Current

Senior Member
250.148 would contain requirements for bonding the box to the EGC. If there is no EGC pulled in the raceway then the raceway would have to be the EGC, and should inherently bond to the box via the raceway termination to the box.

If you are asking about a jumper from the box to the receptacle - that is covered in 250.146. A summary of that is that if there is metal to metal contact between the receptacle yoke and the box (presumed to be connected to be bonded to the EGC) then that connection is suitable for bonding the receptacle, or specially designed devices(often called self grounding) can be allowed to do the bonding in cases where there is not direct metal to metal contact between device and box. Raised device covers that meet requirements in 250.146(A) can also be used without any additional bonding jumpers for providing EGC to the device and it doesn't matter if a EGC has been pulled in raceways or not, but if they have been pulled they must have a connection to the box if the box contains splices, devices or other connections involving the contained conductors.


I did see that in the Mike Holt book, and it said it was for the purpose of working on the receptacle without breaking the ground fault circuit.
 

iwire

Moderator
Staff member
Location
Massachusetts
Oh ok, yeah i knew about that, i was just wondering about the screw, if there was a code stating that it had to be green, but then it was mentioned that the pigtail is not even a code.

The wire must be green or bare, the hardware connecting the wire to the box may be any color or no color at all.
 

kwired

Electron manager
Location
NE Nebraska
I did see that in the Mike Holt book, and it said it was for the purpose of working on the receptacle without breaking the ground fault circuit.
Removal of the device is not permitted to interrupt the continuity of other portions of the equipment grounding conductor - that is likely what was being mentioned, there are several possibilities of how all the items required to be bonded to the EGC could be done and not every installation will have all the same conditions either. But in general that is why there is only a single lead or jumper going to the receptacle itself.

The wire must be green or bare, the hardware connecting the wire to the box may be any color or no color at all.
No color at all - would seem to me it is either transparent or missing :)
 

iwire

Moderator
Staff member
Location
Massachusetts
Removal of the device is not permitted to interrupt the continuity of other portions of the equipment grounding conductor - that is likely what was being mentioned, there are several possibilities of how all the items required to be bonded to the EGC could be done and not every installation will have all the same conditions either. But in general that is why there is only a single lead or jumper going to the receptacle itself.


No color at all - would seem to me it is either transparent or missing

Transparent would be legal. :thumbsup:
 
The screw on the receptacle is more the problem of the manufacturer then it is for me - nearly all of the time. If the screw is missing from the receptacle then it may be my problem to ensure any replacement is green. The screw used to bond the box (if one is used) is not required to be green.

If a screw is missing from a receptacle I generally circular file it. The time to "fix it" usually costs more than the receptacle.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
If a screw is missing from a receptacle I generally circular file it. The time to "fix it" usually costs more than the receptacle.

As you well should.

Just being picky here.

A UL listed receptacle will have terminal screws that are 'not readily removable'. Take a receptacle (I just did this) and try to spin a loose terminal screw all the way out with just your fingers. You should not be able to, as the threads on the screw are crimped so it can't be taken out without damaging the threads in the receptacle, and you would need a screw driver to do that.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
As you well should.

Just being picky here.

A UL listed receptacle will have terminal screws that are 'not readily removable'. Take a receptacle (I just did this) and try to spin a loose terminal screw all the way out with just your fingers. You should not be able to, as the threads on the screw are crimped so it can't be taken out without damaging the threads in the receptacle, and you would need a screw driver to do that.

And if you did remove the original screw and then manage to thread in a replacement, it would no longer be "not readily removable" unless you could figure out a way to crimp the threads after inserting the screw. :roll:
And even that is assuming that all you damaged was the threads on the screw and not the threads in the receptacle body.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
And if you did remove the original screw and then manage to thread in a replacement, it would no longer be "not readily removable" unless you could figure out a way to crimp the threads after inserting the screw. :roll:

That's right!!

And even that is assuming that all you damaged was the threads on the screw and not the threads in the receptacle body.

You probably would have twisted the threaded tabs around a little, too.
 

kwired

Electron manager
Location
NE Nebraska
Listing requirements may have changed over the years. Seems like it is easier to remove and successfully reuse said screw on some older devices then it is on most newer devices.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Listing requirements may have changed over the years. Seems like it is easier to remove and successfully reuse said screw on some older devices then it is on most newer devices.

The listing may have changed, or the screws have been backed out and put back in.

Or both. I have some very old receptacles in the garage. One of these days (not today) I'll pull one and check it out.

Just as a trivia question, I wonder when 'not readily removable' requirement was first in the books.
 

iwire

Moderator
Staff member
Location
Massachusetts
So why is it against code to use a 5/16 self taping screw to the box as your pigtail? Wouldnt that be threaded?

It depends on the thread pitch and box thickness.

Most self tapping screws have a very coarse thread on them and cannot be used for grounding.

However, you can buy self drilling / tapping screws with standard machine threads on them, 10-32, 1/2"x20 etc.. Those can be used for grounding.
 

kwired

Electron manager
Location
NE Nebraska
So why is it against code to use a 5/16 self taping screw to the box as your pigtail? Wouldnt that be threaded?
code reference to previous answers:


250.8 Connection of Grounding and Bonding Equipment.
(A) Permitted Methods. Equipment grounding conductors,
grounding electrode conductors, and bonding jumpers
shall be connected by one of the following means:
(1) Listed pressure connectors
(2) Terminal bars
(3) Pressure connectors listed as grounding and bonding
equipment
(4) Exothermic welding process
(5) Machine screw-type fasteners that engage not less than
two threads or are secured with a nut
(6) Thread-forming machine screws that engage not less
than two threads in the enclosure
(7) Connections that are part of a listed assembly
(8) Other listed means

Two threads of the typical 10-32 screw that is commonly used is 2/32 = 1/16 inches. That means the box thickness has to be 1/16 inch or you will not get enough threads engaged with that type of screw to meet this code section. I believe that is part of reason why it is more common to see a raised bump in many boxes today where they intend you to install a grounding screw, as I wouldn't be surprised to see the wall thickness being less then 1/16 inches.

Not sure exactly when it was added but older codes did not have condition 6 which does allow a self tapping screw, but still requires it to have fine enough threads to have two threads engaged when installed.

Other listed means would work if you found a self tapping screw that was listed for the purpose - but I would guess you won't find any.
 

arknack

Member
Location
Jackson, MI
Grounding raised bump

Grounding raised bump

code reference to previous answers:




Two threads of the typical 10-32 screw that is commonly used is 2/32 = 1/16 inches. That means the box thickness has to be 1/16 inch or you will not get enough threads engaged with that type of screw to meet this code section. I believe that is part of reason why it is more common to see a raised bump in many boxes today where they intend you to install a grounding screw, as I wouldn't be surprised to see the wall thickness being less then 1/16 inches.

Not sure exactly when it was added but older codes did not have condition 6 which does allow a self tapping screw, but still requires it to have fine enough threads to have two threads engaged when installed.

Other listed means would work if you found a self tapping screw that was listed for the purpose - but I would guess you won't find any.

Actually, I thought the raised bumd was there to provide clearance for the screw projection so you wouldn't have to drill a divit in a concrete wall to mount the box.
 

kwired

Electron manager
Location
NE Nebraska
Actually, I thought the raised bumd was there to provide clearance for the screw projection so you wouldn't have to drill a divit in a concrete wall to mount the box.
It comes in handy for that, but that may not be the only reason for it. Like I said if the box thickness isn't 1/16 inch then you don't have enough threads to meet code, but those raised bumps are always thicker then the rest of the box. And like everything else I can see them making boxes out of thinner material then they used to for saving a little on cost. I have not measured the thickness of any so I don't know how thick they are.
 
Status
Not open for further replies.
Top