As best I can tell, the National Electrical Code 2011 allows electrical non-metallic tubing ("smurf tube" or ENT) to be used for running 120 V electrical wire. But everywhere I look, I see remarks to the effect that its use is mostly confined to low-voltage wiring (communications, alarms, audio/video), and some localities forbid its use for 120 V electrical purposes. Why?
I am planning to install a couple exterior weatherproof boxes. The wires will be run from the basement, through the sole plate, into the wall space, and out through a hole drilled through a brick veneer into the back of the box.
To make the bridge from wall to box watertight, I plan to run the wire in conduit. Options here seem to be liquidtight flexible metallic/non-metallic conduit, PVC, or some of the heavier metal conduits like intermediate metallic conduit. All of these seem like a pain to run through finished walls aside from the liquidtight flexible stuff, and that seems like a pain because of its weight and fittings.
ENT seems very attractive next to these: lightweight, easy to flex, easy to attach, works great with non-metallic boxes. It's allowed in damp locations (362.10(4)); the conduit run will be entirely within the wall and terminating in the rear of the box, so none of it will be exposed to the exterior or direct water. What am I missing here?
Best Answer
I don't know why it might be disallowed by local codes. As mentioned in the comments to the question, this stuff is often put into poured walls and floors. It is used quite heavily for 240V wiring and phone/data wiring in Israel where almost all construction is concrete. We also used it for both 120V/240V and data in WaterShed here in the USA.
As another answer mentioned though, it's not good for outside use.