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Imran Malik · Feb 21, 2006, 03:44 PM

I have a detached building with a block foundation. On the inside, the top of the blocks is about 4" above the concrete floor. The walls are aligned with the outside of the 8" wide block therefore there is a 4" wide shelf (top of the blocks) that runs along the perimeter of the building. I used this shelf to run all wiring as opposed to drill holes in the stud. I thought, if need be I will place something in between the concrete block and the wire bundle to better protect the wire. This chase will be closed with a baseboard (side and top) so that the wire bundle will be more than 1 1/4" away from any nailing surface, so I am hoping there will not be a need to install a metal plate of any sort.

Well it is time to get ready for inspection (I am not required to have one done but thought it be a good idea for insurance purposes). So the question to the collective is, Do I need something in between the Romex and the concrete? If I do will the foam seal (used under exterier walls and comes in a roll) work?

Regards,

Imran Malik

tkrussell · Feb 21, 2006, 04:56 PM

We will get to the Romex vs. Concrete Block later.

You need to be careful bundling Romex, or any cable for that matter, long distances, due to the possibility of heat in the bundle caused by electric loads.

As you collect cables you need to know how many of each cable is a current carrying wire, and the bundle will be subjected to derating factors as per code as the quantity rises. As 4-6 wires= 80% of ampacity, 7-9=70%, 10-20=50%.

You usually need to use the next size wire, in general, for all the cables. This gets expensive.

Many inpectors frown on the practice of bundling cables and consider it a low budget method.

As far as the Rx on the block, as long as the block is dry, and the cables are protected from nails, screws, etc. then no problem.

Imran Malik · Feb 22, 2006, 07:06 AM

Tkrussel,

Thanks for the quick feedback. I will verify the maximum # of wires but believe there are no more than 3 or 4. Also they are not tied in a bundle as I was concerned about heat. The confined space would endup being 4" x 2" after baseboards, perhaps I can increase that to 4" x 4" because that space is not really usable.

Regards,

Imran