Electrical – Is it okay to protect NM Cable in an unfinished basement with ENT


Adding a 20 amp subcircuit (120V) to furnace room to turn it into a workshop. Initially it will have one duplex and 2 fourplex receptacles, the fourplex receptacles will be on cement walls, the duplex will be on a stud.

I know that for the duplex I just need to staple the cable back far enough so that if someone ever puts drywall up there will be no danger of hitting the wire with a drywall screw.

Section 334.15.c of the NEC 2011(which the state of MI uses) says

…Nonmetallic-sheathed cable installed on the
wall of an unfinished basement shall be permitted to be
installed in a listed conduit or tubing or shall be protected
in accordance with 300.4.

I'm assuming they mean UL Listed conduit or tubing, which the smurf tube I'm looking at is. Am I correct in this assumption? Also, is this common practice, using ENT on exposed walls to a metal box? I know that the metal box (and metal tubing if I used it) has to be grounded, just making sure I'm not being too unorthodox with solution, or going against code.

Best Answer

You'll have to check with the Authority Having Jurisdiction, but I'd say "smurf tube" on a wall in a shop is a no no.

National Electrical code allows ENT for exposed work, but not where subject to physical damage. Which means if you're trying to protect your cable from physical damage, you can't use ENT (unless you protect the ENT from physical damage as well).

National Electrical Code 2014

Chapter 3 Wiring Methods and Materials

Article 362 Electrical Nonmetallic Tubing: Type ENT

II. Installation

362.10 Uses Permitted.

1) In any building not exceeding three floors above grade as follows:

a. For exposed work, where not prohibited by 362.12
b. Concealed within walls, floors, and ceilings

362.12 Uses Not Permitted. ENT shall not be used in the following:

(9) Where subject to physical damage.

If you don't want to use metal conduit, schedule 80 PVC conduit is identified for areas of physical damage.

Article 352 Rigid Polyvinyl Chloride Conduit: Type PVC

II. Installation

352.10 Uses Permitted.

(F) Exposed. PVC conduit shall be permitted for exposed work. PVC conduit used exposed in areas of physical damage shall be identified for the use.

Informational Note: PVC Conduit, Type Schedule 80, is identified for areas of physical damage.