Conduit in Attic


  #1  
Old 03-13-04, 02:10 PM
smiholer
Visiting Guest
Posts: n/a
Conduit in Attic

Some areas of my attic are extremely hard to get to, especially where the wires head to the breaker box. I am thinking of putting some 2-2 1/2 conduit at the top of the panel leading 15-20 feet into the attic. So basically, I have to work hard one time getting the conduit up there, rather than many times as I upgrade the wiring.

Question(s): What needs to be done with the wiring as it exits the conduit in the attic? Can the wire just be stapled down? I don't need to have the conduit exit into a box, than have each wire exit the box, do I?
 
  #2  
Old 03-13-04, 03:15 PM
u2slow
Visiting Guest
Posts: n/a
If you terminate this large conduit in the panel, then a junction box would have to be installed at the opposite end in the attic. Each cable needs to be secured to this junction box with a proper connector.

What you could do instead is run a piece of built-in vacuum piping or PVC conduit from *near* the panel to the attic and use it as a sleeve.
 
  #3  
Old 03-13-04, 03:31 PM
smiholer
Visiting Guest
Posts: n/a
I think I understand what you are saying about the conduit and the panel...

I have about 2' between the top of my panel and the ceiling that is currently exposed. I was considering putting some type of access panel/door in that area to make future wiring a little easier. Would I be okay with simply starting the conduit at the ceiling, instead of the panel?

So, if one were to look behind my future access panel, they would see 2' of NM leaving my panel, and entering conduit. Then the wire at the onther end of the conduit can simply exit with out a box.

Sound good? I appreciate the help.
 
  #4  
Old 03-13-04, 04:31 PM
W
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Likes: 0
Received 0 Likes on 0 Posts
Keep in mind, however, that if you run a number of cables in a single conduit, for anything more than a short distance for physical protection, then you will need to 'derate' the cables.

The reason is that heat damages insulation, and current running through the wires produces heat. If you bunch a number of cables together in a single conduit, then they cannot dissipate the heat, and will get hotter. Too many cables, and the temperature gets too high for the insulation, and then the cable fails. To prevent this, the allowable current in the wire needs to be reduced.

For example, if you put 5 12/2 NM cables through a single conduit, you could only use 15A breakers on these circuits.

The normal derating rules say that for 1-3 conductors there is no derating. For 4-6 conductors you derate to 80%. For 7-9conductors you derate to 70%, and for 10-20 conductors you derate to 50%. 12ga 90C wire has an 'ampacity' of 30A, though for other reasons you are limited to using 20A breakers...this means that for 12ga wire you don't 'see' the derating requirements until you hit 10 current carrying conductors in a single raceway. 12/2NM has _two_ current carrying conductors.

-Jon
 
  #5  
Old 03-13-04, 04:32 PM
u2slow
Visiting Guest
Posts: n/a
Sounds good, but I recommend using a non-metallic conduit for the task. A metallic conduit presents a hazard if it is not mechanically connected to the electrical system.

Jon is right on the money with derating. Essentially, the more wires you have in conduit, the larger the conductor needs to be to safely deliver the same power.
 
  #6  
Old 03-13-04, 07:39 PM
smiholer
Visiting Guest
Posts: n/a
All sounds good, and I understand.

Anybody know how big of a non-metalic conduit 4 12/2 NM lines would need to slide through with relative easy, including a few 90 degree turns... 1 1/2"? 2?

Thanks again
 
  #7  
Old 03-14-04, 04:08 PM
HairyKnuckle's Avatar
Member
Join Date: Mar 2004
Posts: 77
Likes: 0
Received 0 Likes on 0 Posts
conduit

I added conduit, I think it was 1 1/2 inch when I built my house, from the basement to the attic above the second floor. I have since pulled two 14 gauge wires thru and 1 cat 5 cable. I think I could do one more romex wire before it becomes too close. I did not put in any 90 degree angles, I chose 2 45's where I had to turn.

I would use the 2 inch if you need 4 romex circuits.
 
  #8  
Old 03-15-04, 10:30 AM
T
Member
Join Date: Jan 2002
Location: Chicago
Posts: 1,915
Likes: 0
Received 0 Likes on 0 Posts
You're really not supposed to run data and line wires parallel to eachother, let alone in the same conduit. You're asking for trouble. If something "bad" were to happen, you could have 120V AC run on the data cable, which will fry anything that the cable's connected to. The fact the you have interference is also another reason.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: