ground screws in metal boxes

[iwire]

I do this all the time!

Then it must be OK. :grin:

How far apart from each other do the boxes have to be before you feel 250.148 applies?

'Ground' screws are not listed?) -

I have said that many times and will continue to.

There is no such thing as a 'UL Listed' grounding screw.

 

[realolman]

I like the arlington nipple... I've never seen one before.

NEC or not, I never liked putting two boxes together without locknuts on each side of each box... just doesn't seem right somehow.

 

[e57]

Then it must be OK. :grin:

How far apart from each other do the boxes have to be before you feel 250.148 applies?


There is no such thing as a 'UL Listed' grounding screw.

Darn tootin' it is! If its good enough for me.... Seriously I don't see an issue with it. And opening pandoras box in this area - will open it in another area (as mentioned) say not using chase nipples for other applications.

Not code - commentary...

Bonding around prepunched concentric or eccentric knockouts is not required if the enclosure containing the knockouts has been tested and is listed as suitable for bonding.
The methods in (a), (b), and (c) of the exception to 250.97 are permitted for circuits over 250 volts to ground only where there are no oversize, concentric, or eccentric knockouts. Note that method (c) permits fittings, such as EMT connectors, cable connectors, and similar fittings with shoulders that seat firmly against the metal of a box or cabinet, to be installed with only one locknut on the inside of the box.

A chase nipple is a simular fitting, and the code mentioned here the wording is "such as" - it does not list all or exclude any.

(c) Fittings with shoulders that seat firmly against the box or cabinet, such as electrical metallic tubing connectors, flexible metal conduit connectors, and cable connectors, with one locknut on the inside of boxes and cabinets

I also see this suitable for 250.96A


Are regular lock-nuts listed for grounding? Is the connection between an extention ring or mud ring? I see this as no different, even better in the case of extention rings. If there were a space between the boxes. I would not be using a chase nipple. Nor would I if the box has a raised ground screw mounting, not all do. And the box without the screw is not the path for fault current for any EGC's in or out of either box.

In 250.148:

joined within the box or to the box with devices suitable for the use.

They are joined in the box, and joined in the next adjacent box, joined to that box, and both boxes joined with a device I see as suitable for the use.

 

[iwire]

Forget about the chase nipples, lets say they are listed for grounding.

250.148 requires a the connection of the EGC in each box if the associated circuit connectors are spliced or terminated in that box.

There is no exception for boxes that are right beside each other.

I am sure your way is safe, I just don't see it meeting code.

 

[iwire]

They are joined in the box, and joined in the next adjacent box, joined to that box, and both boxes joined with a device I see as suitable for the use.

Using that logic we would never have to land the EGC to the box supplied by a metal raceway system.

 

[Energy-Miser]

CMPs for the last 100 years (or so) disagree with you. EMT is good enough.

I have seen them knocked off of the couplings many times, forklift hitting a box that stacked next them, set screws coming loose, and generally bad maintenance. The green showing through the gap is alwasy reassuring. e/m

 

[e57]

Using that logic we would never have to land the EGC to the box supplied by a metal raceway system.

That EGC conductor is supplimentary IMO to that metal raceway's use as one in 250.118 - I wouldn't have one unless spec'ed. And with isolated grounds you would be allowed to do just that.

 

[e57]

I have seen them knocked off of the couplings many times, forklift hitting a box that stacked next them, set screws coming loose, and generally bad maintenance. The green showing through the gap is alwasy reassuring. e/m

I have also seen where a fork-lift ripped all conductors grounds and grounded, except the hots of a 50a equipment circuit - if you want to protect against this I suggest concrete bollards....

 

[Energy-Miser]

I have also seen where a fork-lift ripped all conductors grounds and grounded, except the hots of a 50a equipment circuit - if you want to protect against this I suggest concrete bollards....

Yes, and don't forget earthquakes and other natural disasters !! Likelihoods are relavant in any analysis. e/m.

 

[Dennis Alwon]

Forget about the chase nipples, lets say they are listed for grounding.

250.148 requires a the connection of the EGC in each box if the associated circuit connectors are spliced or terminated in that box.

There is no exception for boxes that are right beside each other.

I am sure your way is safe, I just don't see it meeting code.

IMO this section is referring to the circuit conductors and the associated EGC in a box. If there is no EGC in that box then I don't believe it is necessary to have one, assuming , of course, the raceway is listed for the ground.

In other words, if the circuit conductors terminate in Box "A" then the egc must also. However, if the circuit continues without an EGC then there is no need since there is no associated conductor other than the raceway itself.

 

[iwire]

Dennis that is a good argument.

The thing is in this case the EGC is continuing as it goes in the second box to bond the device.

 

[Energize]

IMO this section is referring to the circuit conductors and the associated EGC in a box. If there is no EGC in that box then I don't believe it is necessary to have one, assuming , of course, the raceway is listed for the ground.

In other words, if the circuit conductors terminate in Box "A" then the egc must also. However, if the circuit continues without an EGC then there is no need since there is no associated conductor other than the raceway itself.

In this case, it was back to back receptacles. The circuit conductors were brought into the box without the ground screw, pigtailed to the receptacle and another set of pigtails went though the nipple, ending the circuit run at the box with the ground screw.

 

[e57]

Now say you had an extention box, with MC's in it's KO's - where would the ground pig-tail, and ground screw go?