Longevity of Plastic flexible conduit

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  #1  
Old 02-06-06, 05:11 AM
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Longevity of Plastic flexible conduit

I need to run some low voltage wiring outside (satelite and computer cable). I really need to run this inside some sort of conduit for protection since it will be close to the ground. There will need to be at least 5 - 90 deg. bends. It seems for my purpose that the plastic felxible conduit would be ideal. However, how long can I expect it to last exposed to the weather and sunlight?

Should I use solid plastic or plastic coated metal? I will need at least 3/4 inch inside dia.

Thanks
 
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  #2  
Old 02-06-06, 05:58 AM
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You need schedule 80 PVC. Don't try 5 90 degree bends. Install at least one pull point, possible two. Use outdoor waterproof cables. Conduit installed outdoors is NOT dry.
 
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Old 02-06-06, 08:04 AM
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If you paint the plastic with some latex paint, it will minumize UV damage.
 
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Old 02-06-06, 08:22 AM
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Electrical grade (sked 80) PVC conduit has UV inhibitors in it. PVC expands and contracts quite a bit with temperature, so allow for it. For that same reason, I would avoid painting it. No fun having to repaint it. As for elbows, use sweep els and one or two LBs. or box to pull through. As racecraft said, assume that the inside of the conduit will get wet.
 
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Old 02-06-06, 08:58 AM
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How long is this run, overall?
 
  #6  
Old 02-06-06, 04:58 PM
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The run will be approx. 50 ft total. I need it to go from the attic down to almost the ground (approx. 15 ft.) and then follow a brick ledger (under the ledger if possible) another 35 ft. or so. I will need 1 90 degree bend close to the ground, 1 to go around a brick stair, 1 at the front of the stair, 1 around the other side of the stair, 1 to run parallel to the house and then 1 to go up to a junction box before the cable goes into the house. I guess it'll be 6 bends. I could use the curves for some of this.

Each cable has it's own plastic sheath but only the RG6 is rated for outside (not in conduit). I wanted some sort of conduit to keep the cables together, prevent damage since the cables will be within 6 inches of the ground and to make the installation neater.

I didn't want to use regular metal conduit because I don't want rust stains on my white house in a few years.

If flexible plastic (or plastic coated) conduit is OK, I could bury it around the patio which would be in a curve. This way, I would only need 2 90 deg. bends (1 at the ground below the attic) and one at the ground going up to the junction box. With this setup I would have about 18 ft. exposed to weather / sunlight.

What does everyone else use?
 
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Old 02-06-06, 05:48 PM
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Originally Posted by hdtvluvr
I could use the curves for some of this.
You can't have more than 360 degrees of bend in a continuous run without a pull box for a Code installation. Curves count.

You can bow 3/4" ENT a modest amount.




What does everyone else use?
For what you are talking about and where buried, cheap, utility grade, black PE waterline.


Above ground you might want something prettier.
 
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Old 02-07-06, 04:44 AM
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For what you are talking about and where buried, cheap, utility grade, black PE waterline.
Above ground you might want something prettier.
If I use the PE, will Schedule 80 gray PVC pipe fittings glue to this? If not, how would I make the junction?

By going the burial route, I would have about 12 ft beside a gutter downspout in a location that it wouldn't matter what color the pipe is. The other end will be noticeable from the patio and would be about 3 ft. high. I guess gray would be OK there. How long will gray PVC last in the sunlight?

Thanks

If I can get this settled, what's the easiest way to dig a 60 ft. trench?
 
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Old 02-07-06, 09:13 AM
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If I use the PE, will Schedule 80 gray PVC pipe fittings glue to this?
Not for 3/4" that I know of, but there might be a fitting.


> If not, how would I make the junction?

An insert fitting (which has a smaller inside diameter, obviously.

If you use a 3/4" insert by 3/4" female thread adapter, you can thread half of a schedule80 nipple into that and them glue onto it.

Or you can use a 3/4" insert by 3/4" male thread adapater, a threaded 3/4" sch80 union, and a glue 3/4" sch80 union. Use half of each union.

But unions make a fat knob.
Insert fittings could be sealed with silicone since you aren't under pressure.

They can be made of Nylon, PVC, or brass.

I think you will also find that 3/4" pvc fits right inside 1" PE waterline.
So again, silicone could attach them. I never tried this.
But I believe I've seen waterline repaired with a steel nipple and pipe clamps.


> How long will gray PVC last in the sunlight?
Electrical conduit and Sch80 are sunlight resistant, they bleach out some and weather, but don't deteriorate noticeably.


> If I can get this settled, what's the easiest way to dig a 60 ft. trench?

Hire someone with a good back who like to work hard.
How deep?
You might be able to rent a ditcher, power shovel, or small ditchwitch machine (like a roto-tiller) from a local tool rental.

If you are going deep, you need a small backhoe or a fullsized Ditchwitch (which could do the job in 10 minutes).
 
  #10  
Old 02-07-06, 05:05 PM
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> How long will gray PVC last in the sunlight?
Electrical conduit and Sch80 are sunlight resistant, they bleach out some and weather, but don't deteriorate noticeably.
Thanks for this info and the info about the black waterline. With all of this info, I think I'm ready to tackle the job. Now for some warmer, dryer weather.
 
  #11  
Old 02-08-06, 07:08 AM
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For my underground runs I used 1-1/4" PE innerduct. You won't find this except in large quantities like 1000' reels at a utility wholesaler, but if you get in touch with somebody in the underground construction business, as I did, they sometimes have 'reel ends' that are just taking up space in their storage yard that they will give you or sell to you cheap.

To transition to boxes and electrical PVC fittings, I used Carlon E955 short expansion fittings at $10-20 each. http://www.carlon.com/scripts/emAlbu...cessories&tn=1

PE waterline sounds clever but I don't know if the expansion fittings would work with it. PE waterline is available in various PSI ratings/wall thicknesses, so you would have to measure the actual OD to see if you could use the E955 or equivalent. Others' suggestions may be a better bet for waterline.

I rented a Ditch Witch for 24 hours that would trench up to 4 feet deep at a six-inch width, for less than $250 delivered. If that's not in your budget I saw smaller trenchers at Home Depot for half as much. But if you have any other utilities within 18" plan to trench at least part of it by hand. You will find a duck-billed shovel effective only to minimal depths (at least in the clay subsoil I have) but I was able to use a pointed trenching shovel, digging bar and shop vac at depths up to 4 feet. If you're just digging in topsoil and you're in shape it's a cakewalk.

I primed and painted both innerduct and PVC fittings using Zinsser Bullseye 1-2-3 latex primer and Sherwin-Williams Superpaint exterior latex topcoat. The oldest part was painted in fall 2003 and I've had no peeling or bubbling yet. This section is facing west with full summer sun so it's a pretty good test. On the other hand my wife painted some 1" black PE waterline with no primer and it is peeling.

My innerduct runs are 60' and 75', buried 18" to 36" deep, and this time of year are contracted about 3/4 inch, which is easily measured as the unpainted part contracts out of the expansion fittings.

One final note: Anything plastic that comes in a coil is easier to work with in hot weather. Leave it out in the sun for an hour if you can. I did most of my innerduct work in July and August and it took noticeably less manhandling than when I finished terminations in October & November.
 
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