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Cynthia02 · Sep 11, 2010, 12:04 PM

Is there any reason for not running a total of 4 romex wires through a 1” conduit?

I am rewiring 2 bathrooms and running the wiring from the crawlspace of the house. I need to run 3 12/2 romex (to 3 GFI’s) and 1 14/2 romex across the joists. There is no room for a running board and I do not want to bore holes into the joists. Is there any reason I could not run the total of 4 romex wires through a 1” conduit for 20 feet?

There is about an inch of space because of the concrete block wall, other wires, HVAC, bathroom and kitchen plumbing intake/waste, telephone wires and whatever else I have left out. Everything going on in my house seems to be happening right in this area.

Thank you.

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donf · Sep 11, 2010, 05:27 PM

Cynthia,

Yes, NM cable can be run through conduit but not in your situation.

Article 334.15(C) In Unfinished Basements and Crawl Spaces: reads in-part: "... Smaller cables must be run through bored holes in joists or on running boards."

This is referencing cables less than 2, #6 or 3 #8. you are using #12 cables so that is what you are limited to."

According to the same code cite, NM cable on the wall of an unfinished basement may be placed in listed conduit or tubing.

tkrussell · Sep 12, 2010, 05:01 AM

Romex can be installed in conduit, however, 1" conduit is not large enough for 3 - #12-2 and 1- #14-2 cables.

Don is interpreting the Section 334.15(C) a bit incorrectly, as if Romex could not be installed in conduit on the ceiling of an unfinished basement.

The point that Section 334.15(C) is making is that Romex smaller than the 2- #6 or 3-#8 cannot be simply stapled on the bottom of the joists.

You can do as you propose, however a much larger conduit would be needed. I do not recommend pulling Romex through any conduit of any distance greater than a few feet.

What you can do is install a complete conduit system with boxes and connectors, and pull THHN wire through it, and junction to Romex at both ends if necessary where the cables would then branch off in their different directions.

This can be a 3/4 inch conduit with 7- #12 (6 for the 3-#12-2 plus one for equipment ground) plus 2 #14 for the #14-2, using the one #12 equipment ground already provided.

Cynthia02 · Sep 12, 2010, 10:13 AM

Sounds like the conduit is a bad idea. What about a running board attached to the conrete wall/foundation?

donf · Sep 12, 2010, 05:50 PM

TK, I did not interpret anything. I quoted directly from the 2008 code book.

Cynthia, please reread TK's post. Its not the idea of the conduit that TK is opposing.

He is giving you a better way to accomplish what you want. Also he is letting you know that the 1" conduit is to small to hold all the wires you want to put in it. If you follow TK's solution you will be able to use a 3/4 trade size conduit.