LV in flex conduit

Old 03-04-15, 09:51 PM
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LV in flex conduit

Since my partially finished basement had a flood and mold problem, the lower drywall has been cut away exposing non load bearing studs.

It's a good time to add outlets to this room as well as the room above it, while the studs are accessible.

I thought about adding some LV conduit for future proofing to allow cat5/6, CATV, telco, HDMI, speakers, etc. if needed. Using LV device rings with or without ENT seems to be a common practice. However, another project should leave me with extra 3/4" flexible metal conduit ("Greenfield").

I don't see anything that says I can't use Flex or for that matter EMT. I am not sure if the flex needs to be grounded or bonded to anything for LV. In line voltage, the flex would be bonded at the metal junction boxes with continuous path to ground via the main panel (hopefully!).

Can I use a single-gang LV device ring with a plastic ENT knockout (e.g. to attach the flex or am I required to use metal boxes?

Old 03-04-15, 10:03 PM
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Your mixing high and low voltage in your questions.

If you want tubing for low voltage wiring.... get smurf tubing. It works with those mounting rings you linked to.

If you are putting in receptacles you'll want nail on plastic boxes and I'd recommend using NM cable.

Not sure where you intend to use EMT, metal conduit, in the walls and 3/4" greenfield is not going to fit in standard nailon junction boxes.
Old 03-05-15, 05:50 AM
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You could use EMT or steel or aluminum flexible conduit, but I would also use the ENT (smurf tube) as PJ suggested. If you use metal conduit it does not need to be grounded or bonded for low voltage work. EMT would require an insulating plastic bushing.
Old 03-05-15, 07:44 AM
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The metal or plastic conduit is ok for low voltage. The biggest problem I run into with low voltage stuff in boxes is that some of the keystone blocks and connectors are pretty deep and don't have a great bend radius so it really won't fit in the box. HDMI, DisplayPort, VGA and similar kinds of bulky connectors can be a problem, especially if you don't have the equipment to make field terminations. UTP and coax cables shouldn't be a problem.
Old 03-09-15, 10:34 AM
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Thanks for the info. I'll add a few details of the project and the setup.

Four basement rooms:
unfinished utility room
finished "office" with closet
semi-finished family room, fieldstone walls except for the walls shared with "office, utility room, and bathroom, carpet removed, concrete floor, 1/4" drywall ceiling
the bathroom

Due to the flood/mold damage the lower walls of the office have been removed, making it easy to do a rewire, as the "office" has only 2 duplex outlets. There are no wall outlets in the family room, only two duplex ceiling outlets on the far side of the room, along with one ceiling-mounted four-square dual duplex also on the far side (opposite side as "office" shared wall).

I am about to have the drywall repaired later this month so I want to get the important stuff out of the way and leave room for future expansion.

A previous owner attempted to finish this part of the basement, and fireblocking is non-existing, making wall fishing easier.

Goal 1 (MUST DO, before drywall goes up): add at least two outlets to the office, as well as one GFCI outlet in the utility room (shared wall) and two outlets in the family room (shared wall, both sides of door way.

Additionally, my dining room is right above the office. It only has an outlet on the kitchen shared wall. I'd like to add additional outlets to this room, by fishing them down behind the office stud wall and securing them as they emerge below the remaining drywall. This would be a separate 20A circuit as dining rooms are considered extensions of the kitchen SABC per current code.

I also want to add an outdoor GFCI to the front of my house as the only outdoor outlet is on the rear of the house. The front wall of the house is the same wall as the dining room and office, so again I can fish down.

Goal 1a: I'll ask relevant questions in a separate thread. The switch loop for the office light is run into the office/family room shared wall but the switch is on the family room side and gets covered by the utility room door. I'd like to turn the switch box into a blank-covered box and extend the switch loop over a few stud bays and cut in a new switch box on the correct side of the wall.

Goal 2: leave room for future expansion and do work while the lower stud bays are exposed. In the future I'd like to add a generator circuit (10/3) as well as wiring for additional outlets in the family room (likely EMT coming down from the ceiling and continuing down the wall). Since the family room has a finished ceiling, I'd want to minimize cutting holes. I figure the holes I do cut can be used to mount junction boxes that can act as pull points as well as conduit tees for the wall outlets. I want to fish 3/4 flex down from the family room ceiling down behind the office wall. Having already brought out the fish tape, this is doable, again due to lack of fireblocking. The question then becomes, what do I do with the flex once I get it in the office wall cavity? Do I continue to run it around the room either through holes in the studs or secure it behind the studs on the unfinished side? I could also terminate it into 3/4 EMT and run that around the stud walls terminating the EMT and flex in a common box or use an EMT to flex coupling.

Goal 3: leave room for LV expansion and utilize left over flex cable (hence my question in the OP).

Other design goals: get the cables around the room without interfering with each other and leave enough stud space (especially if I have to use nail plates) for my drywall guy to nail/screw the drywall.

I can post pics if you have any further questions.

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