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I have a finished basement that I'd like to add recessed lighting to. Instead of solid joists in the ceiling, I have floor trusses. In a way, this is good because I don't have to drill holes in the joists in hard-to-reach places. But my concern is that the trusses are held together by nailing plates that might have sharp edges.

The image below gives an idea what's behind the drywall on the ceiling. Is it safe to fish Romex through the trusses near these plates, or should I use metal clad cable instead? Or is there some better way to mitigate the risk? This is a residence in Western PA floor trusses

There's another wrinkle here as well. The junction boxes for the ceiling lights that I'd like to tap into for power to the new recessed lights are all plastic. If I understand correctly, armored cable can't be attached to plastic boxes. So if using armored cable is the best way to mitigate the risk posed by the nailing plates, how do I transition to it from the Romex that goes to the existing ceiling penetrations?

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    Welcome to Stack Exchange. Good catch on the risk to your wiring's insulation. (Don't have an answer, though...) – Daniel Griscom Jan 30 '17 at 21:32
  • Thanks Daniel. So far the only information I've found about wiring and floor trusses concerns new work. The main advice seems to be never drill through the 2x4s that make up the trusses. One person mentioned nailing scrap OSB with 2" holes drilled in it to suspend cable runs when they need to go through the trusses, but that's not possible with old work behind drywall. – sqlsourcerer Jan 30 '17 at 21:49
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I was waiting for our resident sparkies to chime in, but they're either busy or are also short on good answers. So...

I think that this situation is really no different from any fish job... think it through and don't yank. There are always hazards to your cable when fishing blind. If you find yourself pulling against a lot of friction, back up and start over. It definitely helps prevent friction and binding to have an assistant feed cable while you pull.

I've pulled at least a few miles of cable, and the most damage I've seen from sheet metal gussets like those is a partial-thickness shave of the outer sheathing on the cable. I've had worse damage from pulling through wood stud bores around a corner. In the case of the gussets in that photo, all corners are over lumber, so it's unlikely that you'd get a full-grab puncture.

So, yeah. Work carefully, pay attention, and hope for the best.

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