Trenchduct in residential construction

[nmdave]

I'm finishing up plans for a house and I'd like to use something like trenchduct (Wiremold TM) around the edges of the slab (in part because I'm concerned that the rammed earth contractor will leave one or more boxes buried in the walls if I go with conduit in the walls.) However, I don't want something quite so industrial looking. I'd like to cover the "trench" with hardwood or something similar. What part of the code applies to this type of installation, esp in residential use? How are conductors in the trench treated? Trenchduct qualifies as conduit so you can run anything you could run in conduit of similar cross-section. Presumably a concrete trench doesn't qualify as conduit, but what is it? Same as inside a wall? Under a floor? How does the answer change if the cover is removable and the outlets are inside the trench. (ie, lamp cords, etc will enter through grommets and be plugged in beneath the cover.)

Thanks.

 

[pierre]

Re: Trenchduct in residential construction

I would try in advance of the installation, reading the manufacturer's instructions for the product you want to install, and I would read Article 400 before you actually install as per your post.

Pierre

 

[hbiss]

Re: Trenchduct in residential construction

It doesn't look like this product is designed to provide receptacle installation, it's only a duct system. I don't know if it would be permissible with this product to run conduit within and install boxes for receptacles. I think that's what you would have to do. This would come under Article 390.

Assuming that you can do this I would then have a problem with portable cords, particularly lamp cord, running through a hole in the floor cover and plugging into the concealed receptacle. I think 400.8 would prohibit this.

All in all this is a bad idea. Figure out how you can get conduit and boxes in the walls or install floor boxes and raceway in the pour.

-Hal

 

[tom baker]

Re: Trenchduct in residential construction

What about an interior wireway system, divided for power and low voltage. Wiremold and Panduit each make a non metallic system. Feed with smurf tube thru the slab.

 

[nmdave]

Re: Trenchduct in residential construction

thanks for the quick responses.
Yes, it appears that Trenchduct doesn't provide for receptacles. I was just suggesting that as the best comparison to what I want to do. Sorry if I confused folks.

hbiss - I don't think the 400.8 is actually a problem here. Elsewhere on this website under 400.8, the intent for the 2002 change states "The change clarifies that flexible cords cannot be located above a suspended ceiling. However, wiring within a raised floor is permitted, because this space is not considered a concealed space." I think this would cover my proposed situation.

A friend suggested a possible solution of making a two layer structure. The bottom layer would contain the wiring, subject to the standards of any concealed wiring and would be covered with a screwed down cover. The top layer would contain the receptacles, covered with an easily removed cover. This might cover both bases. However, where I'm building is rural, to put the best possible spin on it. The code officials are used to plain vanilla construction and the rammed earth is going to be weird enough as it is. Pushing my luck is not the way to go.

Tom - I had looked at the surface mount products and didn't like the look, and more importantly, my wife and the architect HATED it. I did briefly consider using 1x2" 16ga steel channel as a combination wireway/baseboard, but came back to the question of ever getting it past the local code folks. Smurf tube might simplify life for the rammed earth crew, but it's not clear if it meets code. NM has (I believe) the only rammed earth building code in the US. The code allows rigid or flex conduit to be rammed in the walls, but it must "be able to withstand the pressures of ramming". Testing smurf tube might be more work than just going with EMT.