How to plan for and install (flexible?) conduit

December 8, 2008 11:26 AM

Running conduit for home wiring: I'm convinced. Now how do I do it?

When home wiring comes up on AskMe, invariably someone recommends flexible conduit as the only future-proof approach. Makes sense to me. But there's a lot I don't know.

Big picture: what strategy to use? All routes lead to a central nexus? Should I leave openings in the main routes so I have the option of adding new runs later, or is that for some reason a bad idea?

Small picture: what material? what width? How do you terminate these things and secure the guide-string?

Currently, the house has a disorganized mass of phone wiring, some in use, some not, co-ax for cable that we're not using and don't plan to, and some miscellaneous wiring for things like the doorbell and the thermostat.

The things I'll want to run include Cat5e, some speaker wire, coax (or something) for a TV antenna, and maybe phone cable. From the basement, I have great access to the underside of about half the house, but the other half will be tough and I'll have to rely heavily on tying something to the existing coax and pulling it through by pulling the coax out. I'll need flexible conduit for that, but for some of the runs, rigid would be fine (I'd be interesting in hearing pros and cons.) I won't be running any cable through heating ducts, or anywhere there's expected risk of it getting wet.

My googling has turned up results long on retail product pages and short on strategy and how-to, so I beseech you, AskMe.

posted by Zed_Lopez to home & garden (7 answers total)

Try Structured Wiring. It's pretty definitive as far as the wiring goes.
posted by electroboy at 11:54 AM on December 8, 2008

Unless you know it's possible, most interior wiring is stapled to the studs so you won't be able to pull it out. That includes low-voltage wiring usually. Even if it's not stapled, coax is pretty inflexible and won't pull around a corner. So I would avoid counting on that.
posted by GuyZero at 12:20 PM on December 8, 2008

Since it doesn't have to be grounded, you probably want to use the grey nonmetallic PVC conduit. To negotiate the tight corners, the easiest way to install pull elbows at the 90 deg bends. They have a removable panel that basically lets you make every run a straight line.
posted by electroboy at 1:58 PM on December 8, 2008

Big picture: what strategy to use? All routes lead to a central nexus?

Yes, if possible you want to "home run" the wires, not daisy-chain them. This means all phone wires go back to a single big punchdown, all the Ethernet ports go to a patch panel (so you can have one big core switch and not a million dinky 4-port things), all the cable to a single splitter, etc. It is convenient if all this stuff lives in the same place, probably in your basement near the breaker box.

Are you planning on taking down all the drywall in your house? If not I'm really not sure how you plan on taking the old wiring out, unless it's already in conduit ... which doesn't make sense given how your question is phrased. I don't think you're going to find it easy to get it out, much less to pull flexible conduit into already-finished walls!

Maybe you could convert a house to have conduitized wiring by running all the horizontal stuff in the basement, and then only have short vertical runs going up into the walls below each outlet location. That's the only way I can think to make it work.

The problem with conduit is that you really have to get it in before the walls go up. Once it's in there, it makes pulling wires pretty easy, but putting it into a finished house is really hard. (Unless you're okay having it exposed; surface-mount conduit is a different deal.)

I would basically give up on removing the old wiring, and not even attempt to try and use it to pull new stuff through the walls. That just sounds like a recipe for frustration. I would just cut off and remove the stuff that's in visible locations and let the rest lie inside the walls.

Other random thoughts that come to mind...

Don't bother pulling anything below Cat5E. For any purpose. Even if you're just running "phone wire," use Cat5E and do it just like you're installing an Ethernet jack. When you go to actually put the jack on, just ignore all but two of the pairs, and put a RJ11 on there. Analog POTS will run just fine over Cat5E, and you will be glad not to have cut corners and gone with Cat3 when you want to upgrade to VoIP or something down the road. There is nothing that you can do with Cat3 that you can't do with Cat5, and the cost is very, very small.

There are companies that sell pre-formed combo cables, say 2xCat5 + 1xCoax + 2x14awg, all in one fat cable, for exactly your sort of work. Rather than trying to run the cables separately you just run one big cable and everything you need is in there. It's expensive but saves you time, and makes sure you've pulled everything to every corner of the house. You can get it in a lot of configurations depending on what you want. You'll probably need to go to a real electrical supply house and order it. (Which you should be doing anyway; Home Depot overcharges for a lot of stuff compared to what you can get when buying in bulk from a contractor's supply.)
posted by Kadin2048 at 2:31 PM on December 8, 2008 [1 favorite]

I just want to point out what even though you might not be planning to use it, having coax would probably be a big plus for selling the house, since folks like their cable TV and whatnot.
posted by !Jim at 10:01 PM on December 8, 2008

It sounds like you should probably leave the hard part alone. In my 1880s house, the hard part is always set up weirdly, and frankly, I would have saved days of futzing around if I had just accepted those parts. Note I say this after trying to replace maybe 20% of the older wiring.
posted by bystander at 5:30 AM on December 9, 2008

i just noticed this question.

you can't reasonably expect to be able to pull wires if there is more than 360 degrees of bend in it. total. 180deg in one direction does not counteract 180deg in another direction and result in zero.

because of this, you may need pull-boxes or some kind of fitting that lets you pull the wires. if it were rigid conduit, i'd say use an LB (something like http://www.electrical-supply.net/category.asp_Q_parentid_E_267). it's a bit harder to use with flex, but you should be able to get the flex connected to the LB.

leave junction box and LB fittings and such accessible. also, labels are your friend.

more as i think of it.
posted by rmd1023 at 2:15 PM on December 18, 2008