conduit to in-wall wiring transition


Old 01-24-05, 06:55 PM
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conduit to in-wall wiring transition

I needed to run a new circuit. I tapped into a circuit in the garage. I ran three separate 12-guage conducters (b,w, g), without sheathing (THHN?), in the pvc conduit across the garage ceiling. WHen I got to the appropriate point, I drilled a hole in the ceilling and made the three individual wires exit the pvc directly through the hole into the floor of the next room. No portion of any of these conducters is exposed in the garage. I ran the three individual wires in the joist bay between the ceiling of the gargage and the floor above. Then I ran it to an outlet. The individula wires are stapled, wll back form the edges, in the floor/ceilling bay. The joist bay is covered above and below. Does the code require that the individual wires run in the ceiling/joist bay be sheathed?
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Old 01-24-05, 07:19 PM
Join Date: Sep 2002
Location: welland ontario
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Individual conductor can only run in conduit all the way to there final destination. You can not run them though the floor and up the wall cavity.
Old 01-24-05, 07:20 PM
Join Date: Sep 2000
Location: United States
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THHN must be in conduit at all times.

Adding to the garage circuit is probably a bad idea. In most homes built between 1978 and 1996, that circuit is also serving all the bathroom receptacles, perhaps the outdoor receptacles and perhaps the basement receptacle. This circuit is already doing plenty. I don't know what you plan to use the new receptacle for, but I think you're flirting with disappointment. If my guess about what this circuit serves is correct, it's not even legal to add to it.

Furthermore, you have quite possibly violated building codes by breaching the fire-rated ceiling. Also you have provided a path for car exhaust fumes to enter your bedroom.
Old 01-24-05, 07:42 PM
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The ciruit is a new circuit I added for just outlets in the garage and one in the basement. The only thing plugged in to the circuit is the garage door openers.

Good point on the fire barrier. I didn't even think of that.
Old 01-25-05, 04:54 PM
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Question further question on transition

Would it be ok to:
1) terminate the THHN wire in a surface mounted box on the garage ceiling
2) then make the transition to sheathed wire (ROmex) in the box
3) then exit the back of the box into the ceiling floor space so that I can then go to a box in the room above.

I don't want to do anything unsafe but it seems to me that most garage ceilings have at least one light complete with a box.
Old 01-25-05, 05:32 PM
Join Date: Sep 2003
Location: Central New York State
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Yes, your new transition is okay.
Old 01-25-05, 06:15 PM
Join Date: Jan 2002
Location: Chicago
Posts: 1,915
I hope you used Sch 80 PVC... the gray kind.

Where I am THNN can only be run in metal conduit...inside or outside of the building. I'm sure some areas are different..but I wouldn't run THNN wires in PVC inside. Just a personal preferece.

Why not run pretty EMT on the surface?
Old 01-25-05, 06:39 PM
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The PVC is already up and in place.
Old 01-25-05, 07:20 PM
Join Date: Sep 2000
Location: United States
Posts: 18,497
Just make sure the junction box is permanently accessible. Surface mount on the ceiling would qualify. Seal the opening with fire-rated caulk.

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