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External flexible conduit is too small to fit the many wires I want to run in it

External flexible conduit is too small to fit the many wires I want to run in it

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  #1  
Old 07-23-13, 05:32 AM
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External flexible conduit is too small to fit the many wires I want to run in it

I have a 3/4" flexible conduit that runs for about 3ft from the bottom of my panel down the side of my house and directly under the house. The house is on piers and beams, and there is a good amount of crawl space under it.

Here is my problem. I have about 5 or more electrical wires (Romex 12/2) that I want to run inside my conduit, but it won't fit. The 3/4" flexible conduit is the biggest size that is sold by Home Depot, Lowe's, etc. What should I do?
 
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  #2  
Old 07-23-13, 06:09 AM
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The first problem is that Type NM-B cable cannot be run on the exterior of the house. Conduit and individual conductors or UF cable are run in wet areas.

The other problem is with that many current carrying conductors in one conduit you would need to derate the conductors and you would not have 20 amp circuits.
 
  #3  
Old 07-23-13, 11:20 AM
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What should I do?
Add more conduits and run individual conductors in them to J-boxes where you can splice to Type NM (Romex).
 
  #4  
Old 07-23-13, 12:10 PM
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Yes, you will never get five 12 ga Romex wires through 3/4" flex conduit. Almost all home centers carry larger size conduits, just not always flexible. Your application, especially with so many conductors should use rigid conduit. And, with the proper box and the 90 degree to go under your house it will be much easier to pull wires.
 
  #5  
Old 07-23-13, 02:19 PM
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Your application, especially with so many conductors should use rigid conduit. And, with the proper box and the 90 degree to go under your house it will be much easier to pull wires.
No matter what material you use for the conduit, you will have to derate the wires once you exceed 3 current-carrying conductors in one raceway (conduit). It sounds like you're planning to run 5 circuits, each with its own neutral.

That's 10 current-carrying conductors. The derating factor is 50% You would need to use #8 AWG wires for each 15A circuit and #6 AWG wires for each 20A circuit. I would run multiple conduits to multiple J-boxes.

Your application, especially with so many conductors should use rigid conduit.
The choice of material is up to you, so long as it's acceptable for exposed work outdoors. I personally prefer to use EMT with compression fittings for outdoor work that won't be run in PVC. It's a lot faster, easier and less expensive than cut-and-threaded rigid, and reasonably resistant to damage.
 
  #6  
Old 07-23-13, 03:23 PM
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If they are all going to the same area it sounds like a subpanel may be a better Idea.
 
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