On the verge of pre-wire... Need quick advice...

[footVOL]

Guys,
 
I am on the verge of starting my pre-wire.  I have done this previously, but one thing I kicked myself for last time was not getting a large enough conduit from my crawl space to attic.  My builder has agreed to let me do all my own low voltage, but I want to make sure that there aren't any code gotcha on the back end.  I have a perfect space for a 4" conduit run from basement to attic, but don't know if standard 4" PVC conduit is acceptable for inwall application.  I do plan on putting a firestop collar and firestop plug to cover myself, but don't want to stumble on my conduit choice.  Any pros care to assist?

 

[archstenton]

4" SCH 40 is what? 4.5" o.d.?
 
"In-wall" are we talking a 2x6 wall?, 8" masonry? what is your construction?  Is it a double stud wall for a plumbing chase?

 

[footVOL]

Yes, 4" Sch 40.  It is a dead space that was for mechanical (HVAC) on the plan, but completely unused space that is about 2' x 1' in dimension (left of the front door in attached picture).  There is PLENTY of space for 3 or 4 conduits if I wanted... Just wondering on the code requirements will allow for PVC sealed in a wall, travelling up 3 floors (hence the firestop).  House is a wood frame structure.
 

 

[az1324]

Intumescent Wrap Strip?

 

[Neurorad]

I don't think that is a problem, using the Schedule 40 white PVC conduit.  But, it's up to the sole discretion of the AHJ.  Give him a call.  My AHJ was very receptive to questions, when I ran my basement -> attic 2" x 4 orange flexible conduit.
 
It's possible he may want you to use conduit that is 'listed' for electrical, whether it's rated for low voltage (orange flex conduit), line voltage (blue flex/Smurf, gray rigid Schedule 80), or either (blue flex, gray rigid).
 
I don't think intumescent fire blocking is required for any residential penetrations, but I don't know for sure.  The floor penetrations need to be caulked with 'fire rated' caulk, stamped on the tube; costs a couple more dollars than standard caulk, at HD/Lowes.
 
4" Seems kind of large.  Several 2" conduits might make it easier to add cables, over time.  The cables might tangle and bind less, if multiple conduits - theoretically.  I don't have the experience of having done both.  Maybe DEL will chime in.

 

[Del91574]

Code issues:
 
The conduit, even if not being used, should be electrical rated and listed, not plumbing. I'm also not a fan of flex/smurf/innerduct for pulling through (barring fiber, but different animal)
 
The penetrations, top and bottom plates need to be fire caulked, period. That said, you can actually use fire caulk or believe it or not, high heat stove mastic that carries the same ASTM ratings...this is always a gotcha for code, but if you're in the know and look carefully, it's a difference of 3X the cost (especially in a residence). The only reason why specific colors (blue, red, etc) for fire rated caulks is for identification purposes, and if you use other than the "norm" in your area, you need to leave behind the empty tube for the next AHJ or party to know what was actually installed.
 
As far as plugging the pipe, you can use a seal/plug, or what most people do, install mineral wool and pack firestop on it (putty, etc.) The issue that arises is the material should be replaced after any cabling is installed/run, which is when it usually "disappears".
 
Preferably, I'd recommend at least a pair of conduits, one for HV, one for LV, and IMHO, I like the pipes to terminate at a box/enclosure and then you'll be 100% compliant at all times, and if you're adding field cabling, a bushing, NM connector, etc. is easy enough to add and allow the breakout of the horizontal to the riser. Usually for a length or two of pipe, as long as you're under the maximum bends, I'd set it up to run to an easy location to work from, junction from, stand up and work, etc.
 
It costs more to do that way, but if you're planning on this being "the" house, it's the way I'd recommend.
 
As far as what and how to pull, it's a no win situation about cabling getting wrapped around each other unless you adopt the smaller conduit and filled once it's been pulled in or use a lot of lube when you pull new cabling in. Only way to avoid this is if the pipe is a reasonably straight shot and you run a rodder through it instead of a snake or prebundle cabling (can be bought this way, with a binder wrap).

 

[footVOL]

Perhaps I wasn't clear enough in my initial post. I plan on using grey electrical conduit, just didn't know if this was rated for inwall LV. I also probably should have considered the HV run as well just for future proofing.

This is "the house" at least for a good while. The run terminates in a corner space in the basement, accessible, but tight (well tight squeeze between to studs after dry wall - not 16" OC, or maybe I'm just a little heavier than I used to be). On terminating into a box, I had planned to run my initial runs in a large 4" and plug both ends with firestop just so it makes it easy on the drop from the attic (pass codes?). On the future HV and LV conduits (separate), I will terminate into a box on the low end and plug at the top end.

Any other helpful tips?

 

[Del91574]

Grey ENT is fine for inwall, no special building considerations. Only item to really consider is nail plates where the conduit passes through the framing, but that should be SOP due to bored hole size.
 
The raceway will pass code as long as it is firestopped/draft stopped. Once you run cabling, if it's not replaced or repacked, that would be a violation...but more importantly, the reason why it is would be during a fire, that essentially makes the raceway act like a blowtorch and chimney to the building structure.
 
I like the enclosure idea because while it's not common, it's also not unheard of for critters to use the raceway also.
 
While it's personal preference, I like when the conduits are stubbed and brought out to where they're easily accessable and workable.....or maybe I've gotten lazy in my old age and tired of fighting with framing/insulation, what have you.

 

[footVOL]

Del, 
 
Thanks for the advise.  It looks like this weekend will be a VERY LONG weekend getting things buttoned up before interior starts going in.  At least with the conduit in place I can focus on the 1st floor and exterior/tough locations first, and pull less wire to some non-critical areas.  My last pre-wire I went a bit overboard, some drops got ZERO usage, others had to have a couple of extra drops after the fact.  Live and learn to run less copper and more conduit.
 
Thanks again!

 

[sda]

If you're considering "HV" conduits, using multiple smaller conduits (1/2" or 3/4") would be better.  Even if you have a 4" conduit, once you start putting multiple circuits in it you're going to have to deal with derating.  

 

[Neurorad]

You might consider running your cables outside the conduit, and saving the conduit for future cables. Will make adding cables later easier.

 

[footVOL]

The drop from the attic to basement will be much easier in conduit.  I am going to do multiple conduit runs, (2) 3" (one pre-wire, one for future) and (2) 2" (one for LV power cable for LED spots/gimbals, one for HV future needs in attic/second floor).  I will keep all LV and HV runs separate and all pre-wire and future wires separate.  Based on Conduit Fill Tables, my 3" prewire should still have a little space, with my future 3" being completely empty (so PLENTY of excess space).  My LV run will only have a couple of 14/2 drops in it to begin with so it will also be pretty empty.
 
Once they reach my drop area at the bottom of the conduit, they will run out to different connection points (via conduit) in my mechanical area and server/automation area in the basement depending on purpose (conduits will be further divided by purpose here as well, CAT6 data, CAT6 HDBaseT, CAT5e control, 22/4, etc).  The reason for the organization and division is to keep it nice and tidy.  My last prewire I had ALL my runs mixed up with no real and it became a nightmare of spaghetti.
 
Thanks for everyone's input... I will post some progress pics as they come over the next week.

 

[Del91574]

I wouldn't waste the time/effort running pipe for a prewire purpose and running cable in it while everything is still open....it's a waste and really not needed, nor is the gain what you think it is. In actuality, unless you're very careful or use lube, you'll most likely "burn" the insulation of the cable when you pull each run in next to the other cable. I think some romex staples and ty-raps or D rings would be a heck of a lot easier, then use a bored hole through the lumber. Dress the cabling after all the pulls are complete.