exisiting 120/277v 2x4

[kwired]

I believe ground screw needs to be listed for such means. Example I've seen retrofit can light is supplied with a zinc green color tek screw included with the kit. It's kinda catch 22 because inspectors themselves don't know about this and almost always require documents for the screw or retro can light.


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General rule is in 250.8.

Screw must engage no less then two threads or have a nut on the back side. The typical "ground screw uses 32 threads per inch, so with no nut on the back side that means it must be threaded into at least 1/16" of metal to attain two threads engaged.

Connections that are a part of a listed assembly are permitted even if they break the other rules here, the listing covers them.

Only place NEC requires a green colored screw is for main bonding jumpers that are screw type jumper (the bonding screw for panelboards and disconnects for the most part).

 

[JFletcher]

I see this post is a month old and probably already resolved, but since I noticed the date after I typed out all the following...

Note that you cannot use a nut instead of two threads with a self-tapping screw.

mobile

Self tapping screws would cross-thread in a nut made for a machine screw.

OP, if the fixtures were old enough to be replaced in the first place, then they very well be on the verge of needing new ballasts anyway, even if the 277V ones work on 120V. It's not like 4 bulb 120 - 277V ballasts are expensive anyway:

https://www.1000bulbs.com/product/6...rXzO7w8m3uzguwlD9W6SGvZ6E9U9iTK1MYaArhq8P8HAQ

 

[roger]

I believe ground screw needs to be listed for such means

No, screws used for grounding or bonding do not need to be listed and do not need to be green. Look at most mechanical lugs used for this purpose, they are normally attached with run of the mill screws, bolts, and nuts.

Roger

 

[roger]

General rule is in 250.8.



Only place NEC requires a green colored screw is for main bonding jumpers

You might want to look at 406.10

Roger

 

[kwired]

You might want to look at 406.10

Roger

Right, but that screw is already installed for you, unlike the panelboard bond screw that if you lose it, you may be tempted to use whatever fits.

 

[ronaldrc]

Right, but that screw is already installed for you, unlike the panelboard bond screw that if you lose it, you may be tempted to use whatever fits.

Its hard to believe you can't use a self tapping screw but you can use that little green slide clip.

Ronald : 0

 

[kwired]

Its hard to believe you can't use a self tapping screw but you can use that little green slide clip.

Ronald : 0

Those clips look cheesy, but most don't let go all that easily if you are trying to remove them. Too little amount of thread engagement leads to poor connection, the spring clip at least does maintain pressure to make good contact.