Securing flexible conduit

I've getting close to starting a major addition to our house. I'm going to put some kind of conduit in the new sections of the house for low-voltage wiring. I'm pretty sure I'm going to use the Carlon flexible conduit (the stuff they call "Resi-Gard"), but I'm not committed to it (if someone has a better suggestion, I'm open to it). I'm planning on running 3/4" conduit from all of the boxes back to a central location.

The contractor's electrian wasn't that interested in doing the conduit, but the contractor didn't have a problem with me doing it. I used the Carlon stuff in one room in the basement that I remodeled, and it worked out fine ... except for one issue.

I hadn't fully appreciated how much of a pain it was to secure the conduit to the framing members. I used the PVC "hoop" style clamps, and those worked out okay ... but driving all of those screws took a lot of time, and in some limited-clearance places I was forced to drill & countersink bolts & nuts to secure the PVC clamps. I ended up using a fair number of these clamps, because I didn't want the conduit to move around when I was pulling wire through it.

I have to wonder if I was missing something. What are you supposed to use to secure the PVC clamps to the framing members? Do people nail them? Do you use drywall or deck screws? Traditional wood screws, with a pilot hole? I guess with the rigid PVC, it's less of an issue because you don't need as many clamps. But I had used that in _another_ room I remodeled, and I discovered that I ended up spending a whole lot of time cutting and fitting the conduit with all of the bends necessary (and that room didn't even have that many bends). The flexible stuff was a _lot_ quicker in this regard.

Is combining conduit types an option? I suppose it would make sense to use the flexible stuff where you need lots of bends, but you could use the rigit stuff for long, straight runs.

--Ken

Kerberos Ken H?

3/4" is pretty big. But sure.

Woo hoo! Can't lose with that.

Any reason not to use PVC pipe? Use the flexi-pipe on those odd corners and what nots.

PVC doesn't need quite as much support as stuff that droops.

(and reading ahead, UL is moot with low voltage).

Theory only, but pneumatic nails guns are easy to use and quick.

It's never gonna move or be redone. drywall screw weakness is shear. You don't reall yhave a shear issue in a wall.

I appreciate your want to use conduit - it's future proof and you have the ideal opportunity.

Help us understand what you mean by "UL is moot with low voltage" so that folks in the US aren't mislead into costly and perhaps dangerous errors by incorrectly thinking that "UL is moot with [respect to] low voltage".

Note that the 2002 U.S. National Electrical code has dozens of entries and references indicating UL listing and(or) labeling requirements for low voltage wiring and associated components and equipment including how wiring can and cannot be installed with and without cable ways. The only melt-down I've ever experienced was with 12 volt wiring.

....Marc Marc_F_Hult

Thanks for the tip, I'll check them out.

Attic isn't an option, unfortunately (cathedral ceilings).

It turns out fishing a pull string through is actually dead simple. Tie string to small plastic grocery bag, attach shop-vac to one end of conduit, turn on shop-vac, and place bag in other end of conduit. Zips it right through! With that, you don't have a problem pulling anything.

The one trick with doing _that_, however, is that you should pull a double-length string (I suck the string through, leave a couple of extra feet, mark the end of the string still connnected to the spool with a black marker, and then pull more string until I see the black mark at the other end). That way, when you pull a cable, you can pull from the middle and you've still got the string when you're done.

--Ken

mmmmmmmaybe :-)

That's what I thought ... until I filled it up with two coax and one cat-5. (Okay, it wasn't _full_, but it sure was getting hard to pull the last one). And that was for one box! (Okay, that's an extreme example, since it was for a satellite TV installation).

Weeelll ... I found out from my experience with using it earlier that doing the fitting for it (measuring, cutting, gluing) ends up consuming a lot of time. I think I'll take someone else's suggestion and try combining the two different types.

Good point. Thanks for the advice!

--Ken

You generally shouldn't be pulling them one at a time. It's usually a much better idea to bundle them together and pull them all at once. Granted, there's always the situation of adding wires later, of course. That's why it's often just a better idea to pull more than you need immediately. Due usually to the hassles of re-pulling /everything/ because adding something new broke something old.

The only 'downside' to flexible corners pertains to stuff getting caught in the bends as you pull something new. You end up yanking one end of the flexible tubing out of the conduit. The do make conduit with large bend raduis curves. In general it's an extremely unwise idea to use regular PVC elbow joints. Almost all wire has bend raduis requirements (cat3 for telephone and speaker wire are perhaps exceptions) and it's much wider than what the elbows provide. Even fiber has bend radius requirements.

-Bill Kearney

3/4" is not pretty big. Now I'm looking at it from a commercial installation as apposed to a residential, but our minimum size is 1 1/4", and that is for three Cat6 cables. And NEC code for 3/4" is 4 cable with and OD of .25". So, I would call 3/4" the absolute bare minimum.

Anyone know how well this technique works with cable in the conduit already?

When I put in pull strings, I make it double length also. But when I'm done pulling another cable, I pull the string back so I can use it again. This technique has a limited life span though, as the pull string gets increasingly tangled with the cables after each pull.

Wouldn't use anything smaller than 1.25 for runs over 25' ... a 100+ foot run with two cat5's and two coax proved that the choice was valid ;-)

In addition, have quit using cord and only use single strand electric fence wire... size depending on what I expect to pull and include a length of pull wire with the cables that will remain in the conduit for future use.

However, have found that normally the only practical method to add wire is to "pull back" the existing wires dragging a pull cable... attach the new cable and pull all back as a unit.

Beverly Howard

For a good strong pull string use "Mule Tape" which is available from Graybar and others. When I put 200' of utilities underground so we could have 3 ugly poles taken out the phone co. required that we place Mule Tape in the conduit rather than the poly twine we used. Since I had to buy a 1000' spool to get the 200+' I needed, I used it everywhere else and it has saved my butt a few times. It has a tensile strength of 2500# so even crushed conduit was still usable!

From:Beverly Howard snipped-for-privacy@SpamSucksBigTime.com

Justin T. Clausen wrote: ....

Well in commmercial sure. Under our raised floors was have long runs of 4 and 6" conduit. Because we have room.

I still dunno how you run conduit inside walls horizonally. I'd suppose up or down to where you have 'tween space.

I envy those who have no walls up yet. I'd drop 2" pipes up and down through the house.

Hell, between upstairs and downstairs is a good 18" for air heating. I'd run 4" pipes if I could. It would be ideal to home-run both upstairs rooms and downstairs rooms. But it's all sealed up.

But yeah, I ran 1" holes through a couple sills with thoughts to put PVC in (yeah, right. Not without ripping out a wall above or below.)

It's a not yet tight for 4 CAT5's, a couple coax and some 3 wire audio. But it's close.

And Ken is the sort to have too many things running wires (but cut into those wires to listen and you'll get nothing useful :) ).

for more info on mule tape

From:Beverly Howard snipped-for-privacy@SpamSucksBigTime.com

Sure, _now_ you tell me :-) Thanks for the tip ... in this particular case, I had only one spool of coax, but that's pretty cheap. Next time I'lll just buy another spool. (Too bad Home Depot doesn't sell them in double rolls).

Sure, I know about the minimum bend radius. The PVC rigid conduit they sell at Home Depot has very nice elbows with a very gradual radius. Shouldn't be a problem. Thanks for the advice!

--Ken

I used Carlon Innerduct - may be the same as Resi-Gard.

3/4" is pretty small. I used various sizes. The 2" size is a little hard to bend and work with. Anything under an inch is much too small. After trying several sizes, I found 1.5" to be the best overall. The stuff is amazingly cheap.

One trick I used that hasn't been mentioned in this thread. Just before pulling wires through the conduit I got the idea of pulling the initial set _alongside_ the conduit so as to leave the conduit space for future use. This was really easy to do with the walls open.

At each end of the conduit, I fasten them to the stud nearest the wall box with a simple screw. I used plastic open end boxes which are fastened to studs, so the conduit terminates nearby.

Larry Alkoff aka Austin Reed