I am installing some recessed lighting cans into a ceiling already drywalled with no access above the drywall. I am using the remodeling cans with the metal junction box attached to the can assembly.

I will have two, 3-wire 12 gauge cables coming into the junction box for each light. This is the typical wiring with shielding I see in construction. When I remove the knockout, the hole is quite sharp and I am fearing that over time, this could cut into the wire. Also keep in mind that since I have no access, I will not be able to put a staple on the wire/stud to keep the wire tight.

My question is this. How can I apply a bit of protection and create a grommet if you will to fill the void around the hole and make the wire secure so I do not worry about the box cutting into the wire? I have contemplated wrapping considerable electrical tape around the two wires, or using some form of silicone.

Also, is this truly a concern, or am I being a bit extreme? I know these boxes are used all the time and I do not believe others protect the wire.

Thank you!

 

When you remove the knockout you are required to install a cable clamp. This clamp provides the protection you need from the sharp remainder of the knockout.

 

I assume I can get this clamp at Home Depot?

 

Yes. Might I also suggest you pickup a good boook on wiring. A good book on wiring will go over all this sort of stuff with you. No offense intended, but you should probably learn the basics to make sure that your installation is safe and will pass inspection.

 

No offense taken. I am actually one who people may deem too much of a reader. Oddly enough, I have a few books, one actually dedicated to wiring and I was unable to find any information on this… In addition, I would also have though the instructions of the light would have alluded to this configuration, though it states just to push the wire through the old knockout.

Thanks again.

 

The recessed fixtures I have used have two types of knockouts. The smaller oblong knockouts in the corners of the box have NM clamps integral with the box - no additional clamp is needed. The integral clamp is a metal clip riveted to the box that the NM cable passes under when you shove it through the knockout.

The round knockouts in the middle of the box sides require the separate clamp.

 

You say:
"This is the typical wiring with shielding I see in construction."
Do you mean BX, with the spiral metal sheathing? Or Romex with the white or yellow plastic sheathing?
Any wire needs a connector at a metal box or enclosure.
Romex can be put into the small openings with the built in clamps if they exist. If not use a Romex connector into the round knockout. BX or MC need a BX or MC connector installed into the round knockout.

I must agree that the fact that you are even posing this question concerns me. Perhaps someone a little more quaified shoud be doing this installation.
A bumper sticker I once saw: "Wiring's no hobby, call a licensed electrician"