Some questions about running conduit

E

ellesshoo

New Member
I've searched all over and either I'm not using the perfect keywords or I find info that I'm unsure whether it applies to my situation. So here goes...
 
I'm planning to run some conduit for low voltage/networking wires that will go between floors (basement, 1st floor, 2nd floor, partially finished 3rd floor/unfinished attic). I'm trying to understand the appropriate fire blocking method. I understand there needs to be fire blocking material around the conduit penetration between floors but does there also need to be fire blocking INSIDE the conduit? If so, what use is a conduit anyway since, I would assume, it would negate the perceived benefit of being able to easily fish wires in the future? If there doesn't need to be fire block inside the conduit, then what's the difference between having an open ended conduit running between floors vs an unprotected hole between floors? Seems fire could just as easily spread between floors through conduit (if it starts at one end of the conduit) as it would if it started on one side of a bare hole in the floor plate. I must be missing something. Thanks in advance for any info/explanation.
 
Welcome to CT!
 
This is a good question, and something I need to figure out myself.  That said, central vacuum systems would have the same problem, so I am guessing it's just around the pipe, but just a guess.
 
This just depends on your local inspector.  You may have to terminate your ends of the conduit into boxes to satisfy the inspector.
 
Stick some mineral/rock wool in the top and bottom of the conduit.  This will prevent/resist fire from entering in the bottom and air(oxygen) from entering in from the top.  And make sure to use CM jacketed wire, which is combustion resistant.
 
David
 
I have another question, how should one handle the need to have wires terminate at different places. For instance, let's say I have a conduit running along a 2nd floor joist and then turn down to a termination/box ( first floor) but I need one of the cables to do something at a point in the ceiling (like a smoke detector). I can't visualize a simple way to accomplish this other than having the appropriate wire exit the conduit as it passes the point in the ceiling. Is that how it should be done? Having 2 sections of conduit with a gap at that point would make it impossible to pull wires through the whole thing though.
 
Realize that conduit in a home is generally not meant for wiring while you have the walls open.  It is meant for running wires at a later date.  So if you have the walls open, I'd recommend running your wire where you need to and leaving the conduit for future wiring needs. 
 
Now, to assist with future wire pulls, you could tie some string at the top and the bottom that will allow you to tie your wire to the string and then pull the wire up with the string.  Your string would need to be at least twice the length of your conduit to allow you to pull all the way up while still being tied in place at the bottom.
 
David
 
ellesshoo said:
I have another question, how should one handle the need to have wires terminate at different places. For instance, let's say I have a conduit running along a 2nd floor joist and then turn down to a termination/box ( first floor) but I need one of the cables to do something at a point in the ceiling (like a smoke detector). I can't visualize a simple way to accomplish this other than having the appropriate wire exit the conduit as it passes the point in the ceiling. Is that how it should be done? Having 2 sections of conduit with a gap at that point would make it impossible to pull wires through the whole thing though.
Click to expand...
 
 
Don't run something like smoke detector wiring in conduit.  Run conduit where the technology has a reasonable chance of changing or where you don't really know what you might want or you think that you might change your mind later.  Smoke detector wiring doesn't qualify on that count.
 
But to answer your question, run conduit from one box to another box if you want the same conduit to have multiple terminating locations.  Of course every box needs to be accessible. 
 
While stuffing mineral wool into conduit might be partially effective at blocking smoke, if the inspector cares to inspect the conduit at all, that won't fly.  Either you won't have to do anything (because the inspector doesn't care about conduit), or you'll need to put proper terminations to the conduit.
 
Lou Apo said:
I have another question, how should one handle the need to have wires terminate at different places. For instance, let's say I have a conduit running along a 2nd floor joist and then turn down to a termination/box ( first floor) but I need one of the cables to do something at a point in the ceiling (like a smoke detector). I can't visualize a simple way to accomplish this other than having the appropriate wire exit the conduit as it passes the point in the ceiling. Is that how it should be done? Having 2 sections of conduit with a gap at that point would make it impossible to pull wires through the whole thing though.
 
 
Don't run something like smoke detector wiring in conduit.  Run conduit where the technology has a reasonable chance of changing or where you don't really know what you might want or you think that you might change your mind later.  Smoke detector wiring doesn't qualify on that count.
 
But to answer your question, run conduit from one box to another box if you want the same conduit to have multiple terminating locations.  Of course every box needs to be accessible. 
 
While stuffing mineral wool into conduit might be partially effective at blocking smoke, if the inspector cares to inspect the conduit at all, that won't fly.  Either you won't have to do anything (because the inspector doesn't care about conduit), or you'll need to put proper terminations to the conduit.
Click to expand...

"Proper terminations" being what exactly? For an attic-basement run, some kind of cable gland or clamp? I'm guessing most other runs will terminate at LV boxes.
 
Ask your inspector what he wants, then there won't be any troubles.  And I would leave the conduit empty until after you get your co, just to keep that out of the equation.
 
Depending on how long your conduit is and how many bends you have, you may or may not need string pulls.  For long tough runs tie a piece of styrofoam to one end of your pull string and use a vacuum at the other end to suck the string through the conduit.  Shorter runs you can just push wire directly through or use a wire fish tape (personally I find the plastic ones to work best).
 
dgage said:
Realize that conduit in a home is generally not meant for wiring while you have the walls open.  It is meant for running wires at a later date.  So if you have the walls open, I'd recommend running your wire where you need to and leaving the conduit for future wiring needs. 
 
David
Click to expand...
I agree with David. With the walls open, just run the cable without conduit, using inwall rated cable. More info about inwall ratings here.
 
Kevin
 
Kevin L said:
I agree with David. With the walls open, just run the cable without conduit, using inwall rated cable. More info about inwall ratings here.
 
Kevin
Click to expand...
 
The only wires that I would run in the wall would be alarm cabling and speaker cabling.  CAT5/6 will probably have some mix.  I ran most of my cat wire in conduit so I can upgrade or add additional wires in the future.  But the cat wire I ran to my alarm touch pads I just ran in the wall figuring I'll never need anything different there.  
 
CAT wire and alarm wires will almost certainly be in-wall rated by default, speaker wire will be one that is available either way.  There is also plenum grade, but you don't need that unless you are putting inside of air ducts (not the way to do it when the walls are open, mostly that is a way to do retrofits).  I would not run any other kind of wire in the walls bare, all other types I would run in conduit (like hdmi, coax, fiber, etc).
 
I would 
 
Lou Apo said:
The only wires that I would run in the wall would be alarm cabling and speaker cabling.  CAT5/6 will probably have some mix.  I ran most of my cat wire in conduit so I can upgrade or add additional wires in the future.  But the cat wire I ran to my alarm touch pads I just ran in the wall figuring I'll never need anything different there.  
 
CAT wire and alarm wires will almost certainly be in-wall rated by default, speaker wire will be one that is available either way.  There is also plenum grade, but you don't need that unless you are putting inside of air ducts (not the way to do it when the walls are open, mostly that is a way to do retrofits).  I would not run any other kind of wire in the walls bare, all other types I would run in conduit (like hdmi, coax, fiber, etc).
Click to expand...
 
I ran all my cabling without conduit. I didn't want to fill the conduit with cable that was easy to run with the walls open. Plus, with a concrete block exterior walls, conduit is tough to run. For my video, I used RapidRun cables and leads. The cable is incredibly tough, and you can change the ends to different types like HDMI or Component.
 
Kevin L said:
I ran all my cabling without conduit. I didn't want to fill the conduit with cable that was easy to run with the walls open. Plus, with a concrete block exterior walls, conduit is tough to run. For my video, I used RapidRun cables and leads. The cable is incredibly tough, and you can change the ends to different types like HDMI or Component.
Click to expand...
 
 
The reason I run conduit is that those wire types keep changing.  HDMI barely existed 10 years ago, and it has already gone through several upgrades since its inception.  The wire you put in may not handle the new 4x format that is probably going to be standard on larger TV's in a few years.  Even if it does, what is going to be out there 10 years from now?  I'm just saying, some technologies are just changing so fast that these wires should be put in conduit.
 
Alarm cabling hasn't changed in. . . well. . . has it ever changed?  Not in my lifetime it hasn't.  The alarm wire we had in the house I grew up in is pretty much the same as my current house (I'm 44).   Of course I am running it to a lot more things than doors and windows in my current house, but conduit or not, that wouldn't have been helped since I wouldn't have run conduit to those things 40 years ago either.
 
My attic to basement conduits are terminated at the attic floor, and basement mechanical room ceiling, with a simple coupler fitting on each end, attached with PVC cement.
 
034481061069lg.jpg

 
Fire rated caulk around each floor penetration.  
 
Holes in attic floor, put conduit through holes, add fittings to the top ends, fasten conduits to adjacent walls at each floor, cut to length in basement, add fittings at the basement conduit ends, caulk around floor penetrations.
 
At each of the 2 floors between the attic and basement, I attached the conduits to the adjacent wall with plastic conduit D-rings, halfway up each wall. 
 
conduit-clamp_lg.jpg

 
Duct Seal (available at HD/Lowes) is the putty that you can put into the ends of the conduits that have cables in them, to keep critters out.  You can also buy or make foam plugs.  Mine have been open since installing them.
 
Denso-Cable-Duct-Seals1348048819.jpg
 
Lou Apo said:
The reason I run conduit is that those wire types keep changing.  HDMI barely existed 10 years ago, and it has already gone through several upgrades since its inception.  The wire you put in may not handle the new 4x format that is probably going to be standard on larger TV's in a few years.  Even if it does, what is going to be out there 10 years from now?  I'm just saying, some technologies are just changing so fast that these wires should be put in conduit.
Click to expand...
 
Future-proofing is important. I agree, Lou. I ran conduit for future runs, but with the walls wide open while building my home in 2007, I decided not to fill up the conduit with cables. The conduit is there for any future needs.
 
Kevin
 
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