ECN Forum Forums Code Related Discussion NEC & other Code issues Lets Talk About Screws Some More

How about this:

Here I'm using the threaded hole that would have been used for a clamp but there's no clamp needed at this spot. Some older boxes don't have a special ground screw hole.

Wa2ise

I see no problem with that bonding method. 250.148 (A) is satisfied, since the screw/hole is used for no other purpose. Article 314.40 (D) is satisfied, the screw is installed in a tapped hole or equivalent.

Which brings up my question. What the heck does equivalent mean in Art. 314.40 (D)?

Is this covering the use of ground clips?

Where in the code does it cover the use of these so called ground clips?

I personally hate these things. Although for some things they come in handy, like a bath exhaust fan, etc.

Frank

Frank,
Could equivalent mean any of the methods described in..

110.14(A) Terminals Connection of conductors to terminal parts shall ensure a thoroughly good connection without damaging the conductors and shall be made by means of pressure connectors (including set-screw type), solder lugs, or splices to flexible leads. Connection by means of wire-binding screws or studs and nuts that have upturned lugs or the equivalent shall be permitted for 10 AWG or smaller conductors.
Terminals for more than one conductor and terminals used to connect aluminum shall be so identified.

-Randy

PS.. Somewhere, sometime ago, I came across some handy-boxes that had a box-side clamp with a green jumper factory installed... This might be one of those "equivalents"

Randy

Thanks for your thoughts. That sounds good to me. Those ground clips still have me wondering. How can they be accepted as a good means of connection for ground and not a tek screw.

I never seen that type of handy box.

Frank

Oops! Just posted in the other thread what should have been here. Guess my cache needs a flush.

Here, I fixed it.

Ryan
Take a look at the first name on page ix in the McGraw-Hill Handbook.

Pierre

The end of the code section says "listed means", not listed devices. Anyone care to take a stab at what they are really saying?? Is a common 10-32 machine screw a "listed means"?

Thats very impressive, Pierre. You should be proud.

I think we all got a little off track here.
I clearly see a green "ground screw" being used.
The "wrap clockwise" would be a good trade practice, as indicated by the American Electricians' Handbook. If you're going to cite for this, it would be as a workmanship issue. (The earlier handbook citation was specific for aluminum wire).
More important is the issue that was addressed so poorly by the 'no sheet metal screw' clause. We're not engineers, and I can find sources that define anything under 1/2" thick as sheet metal, and any thread form going into such metal as a 'sheet metal screw.' I think we all agree that the NEC stepped in it with that clause.

The issue? Screws of an improper size and thread form to reliably grip the holes that they were put into. Loose screws= poor ground.
IMHO, a Teks screw into its' own hole is a perfectly good connection. Even a smaller diameter "silver bullet," with its' washer head, provides a lot of wire-to-box contact for a good ground.

With this picture, I'm not sure that the hole being used is correctly sized for the screw. As with older boxes, there is no hole specifically sized to take the green screw. With such a box, a Teks screw (or a spring clip) are the only ways to ensure a good connection- unless you want to drill & tap (and I've not seen an electrician yet who has a set of taps as well as number drills on his belt).
Once again, we're not machinists either.

I'd say any connection that can be made tight enough is acceptable. What is "tight enough?" Following both UL and NEMA practices, the ground screw should be tightened to 75 pound-inches. This is best achieved by the use of a socket. See Ferm's Fast finder, or UL 486A.