How many extra runs of conduit in a trench?

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  #1  
Old 06-15-12, 12:08 PM
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How many extra runs of conduit in a trench?

Sometime in the next year, I plan on building a pole barn. I plan on the electric being run underground from the main house panel. Also, I plan to run aluminum conductors in PVC. Question is, how many other runs should I include for future needs? The future could bring a telephone, alarm, and cable TV. Should this be three extra runs, or can these non electrical needs be in the same conduit? Should I run extra conduit in case I ever need to re pull electric conductors? Also, the future could also bring solar panels that I would mount on the barn. Can I assume the same conduit bringing the power from the house, could send power to the house? Thanks. John.
 
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Old 06-15-12, 12:45 PM
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Telephone, alarm and tv can probably be run in the same conduit provided it's large enough to house it.
How far of a run are you doing?
 
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Old 06-15-12, 12:48 PM
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The topography of the land will play a part in where it goes. Could be as far away as 300'.
 
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Old 06-15-12, 01:11 PM
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I assume running CATV, phone, cat5, and other low-voltage cable in the same conduit as your 120v line would be against your local electrical code. If for some reason, the 120v line were to short and jump to one of your low-voltage lines, that could be a recipe for a deadly shock.

Besides, you run the risk of the low voltage lines picking up interference from the 120v lines. Put it in a separate conduit.
 
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Old 06-15-12, 03:57 PM
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I suggest digging one trench and layer it like this:

Communication 1"+ conduit 12" down

Electrical PVC 18" down

Gas line 24" down

Water line below frost line

You might not need them all so just skip what you don't need. Remember, Cat 5 max length is about 100 meters, or 328', of the entire cable length (point to point).
 
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Old 06-15-12, 06:18 PM
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I apologize for my misguided post. I realize that it reads as if I want to install the low voltage stuff in the same conduit as the electric. I know that's a no no. I guess Northern Mike kinda answered my question. I was curious if the low voltage stuff could be together in one conduit, or in separate conduits.
 
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Old 06-15-12, 06:24 PM
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Tolyn, thanks for the info on the CAT 5. Also, never thought about seperating conduit in vertical layers. I was going to evenly space them side by side in the trench. Also, since my conductors might fairly large, depending on the distance, I might go with large radius 90's. So, I might bury the condiut deeper than 18 inches.
 
  #8  
Old 06-15-12, 09:26 PM
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Check with an underground construction contractor in your area to see if they can supply HDPE innerduct for the low-voltage at least, and for 120/240 also if it can be made code compliant. I am guessing it's OK under the utility metering manual but I have no idea how the NEC classifies it.

Innerduct comes on a reel and saves the hassle of cementing all that PVC. It can be terminated to boxes or conduit bodies as needed with regular PVC expansion couplings. If it's useable for 120/240, I would buy whatever size is needed for the power conductors and double the footage so you can make two runs. That way you don't need two different sizes of everything. Of course I'd want to figure the price difference before going that route.

For low-voltage the minimum size I'd use is 1-1/4" and it's hard to imagine a requirement for more than 2".

In this area, on the utility side of the meter, the CATV and Telephone utilities supply their cable to the power utility, and they or a subcontractor put them all in the same trench. Not a lot of effort goes into separation, but it's always a good idea.

Also have you considered directional drilling? It will cost more but it's pretty amazing how easy they make it.
 
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Old 06-16-12, 07:49 AM
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Check with an underground construction contractor in your area to see if they can supply HDPE innerduct for the low-voltage at least, and for 120/240 also if it can be made code compliant
U.L. Listed HDPE conduit is readily available on large reels. It's commonly used in my area with directional boring and utilizing E-Loc couplings to transition the ends to any other schedule 40 conduit, such as PVC conduit.
 
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Old 06-16-12, 08:41 AM
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You may want to consider direct burial cable rather then conduit for the power. You would only need to drop your depth of the power cable to 24" down. You could just flip the gas and power lines I have in my previous post.

As far as the solar equipment goes, just install all the equipment in the garage and any extra power will go back to the house or power grid.
 
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