junction box/ pull box question outdoor wiring

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Old 04-23-08, 10:26 AM
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junction box/ pull box question outdoor wiring

I am using #6 wire going about 100 feet to a subpanel ( carrying 220 volt). I would like to install one or 2 pull boxes / junction boxes along the way. I am using schedule 40 pvc which is one and a quarter inch size for the majority of the run.

I would like to start the run with some existing half inch pipe which is already in place from previous wiring project. It goes for about 12 ft (gets me from my panel to the trench. (goes overhead a outdoor patio)

First question:

Is it ok to run 3 #6 wires (2 hot and neutral) in a 1/2 metal pipe? I am not sure seems kinda tight illegal?

second question:
in the junction box what do I use to connect the #6 wire? I assume I can't twist with linemans pliers and place a wire nut over it as I do with #12, I guess how do I connect larger size wires in a jbox?

at home depot they just handed us a box with no knockouts in it with a gasket and cover on top and said it was a buriable junction box. They said drill holes and then seal with silicone.
I am still kinda confused on exactly how to connect the pipe to the box.

Questions: After drilling the hole into the jbox. do we glue (pvc solvent) the pvc pipe directly into the drilled hole? or are there some pvc female connectors we would first glue into the hole we drilled, then glue the pvc pipe into the connectors?

Question: How deep to we bury the box. Do we just bury the whole box 18 inches down completly covered or do you have to keep the top open to the surface?

last question:are there any Junction boxes that come with knockouts? (avoid drilling if possible)


Sorry so many question...

thanks in advance for any help!!
 
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Old 04-23-08, 10:54 AM
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The 1/2" conduit/tubing cannot be used.

There should be no wiring-connections, or "splices" at any point between the two "end" terminations.--- "If it's not there, it can't fail".

You will have "X" number of 90-degree turns in the "run"-- you can use 90-degee "elbows" and "LB" condulets for these 90-degree turns. An "LB" condulet is a pull-point if such is needed.An "LB" must be used where conduit that is fastened to the exterior surface of a stucture must be joined to a conduit inside the structure.

You are being astute by using 1-1'4" conduit for three #6 conductors; there should not be a problem pulling the conductors if there is not more than four 90-degree elbows between any two pulling-points.

Good Luck , & and Learn & Enjoy from the Experience!!!
 
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Old 04-23-08, 10:58 AM
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Originally Posted by Tim T. View Post
Is it ok to run 3 #6 wires (2 hot and neutral) in a 1/2 metal pipe? I am not sure seems kinda tight illegal?
No, that's not okay. The minimum size for #6 feeder is 3/4". Also, based on NEC2008 code three-wire feeders are no longer legal to outbuildings. You'll need to include a #10 ground and maintain isolated ground and neutral bars at the subpanel if you are on '08 code. Also, if there are any other metal pathways between the buildings (water pipe, phone, tv, computer, etc) then the fourth wire is required regardless of your code version.

how do I connect larger size wires in a jbox?
You can use Buchanan WT54 (blue) large wirenuts for connecting two #6 stranded wires; however, splices in the feeder should be avoided if at all possible. It's best to keep the conductors unbroken from panel to panel.

How deep to we bury the box.
I really prefer to not use underground j-boxes unless absolutely necessary. A 100' 1-1/4" conduit shouldn't be too bad to pull without access boxes. Install a pull rope through the conduit as you assemble the sections, then use the the rope to pull in the conductors.
 
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Old 04-23-08, 12:26 PM
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Thanks for the help!

Thank you! you guys have really cleared it up quite a bit of my questions.

1/2 pipe is now out

Sounds like I dont even need a Junction box is out replaced if needed with a lb

but since they are out I have a couple more questions..

Question: Offhand would anyone know what the nec code minimum digging depth when running pvc pipe under 3 inches of concrete? or how far does the pipe need to be under the concrete?

Question: Is it correct that an LB connector can be buried and would fufill the code requirement for a pull point for every 360 degrees?

Thanks again for the help. Very helpful!
 
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Old 04-23-08, 12:47 PM
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Originally Posted by Tim T. View Post
minimum digging depth when running pvc pipe under 3 inches of concrete?
For concrete that is not a driveway:
If the concrete is at least 2" thick, the pipe should be 12" deep from the surface.
If the concrete is at least 4" thick, the pipe should be 4" deep from the surface (essentially right under the concrete).

For any other area, the depth should be 18".

All depths are measured from the surface to the top of the pipe.

Is it correct that an LB connector can be buried and would fufill the code requirement for a pull point for every 360 degrees?
Neither an LB nor a junction box can be buried, because that makes it inaccessible. If you need a pull box, the top of the box needs to be exposed to the surface. Is the trench layout really so complicated that you can't lay it with less than 360?
 
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Old 04-23-08, 01:15 PM
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thanks for concrete/ lb box info..

Thanks again. I am getting all my questions answered today. Great site.. Ive been trying to figure this stuff out for a while very helpful

Is the trench layout really so complicated that you can't lay it with less than 360?[/I]

I basically had to add an extra 180 degrees in turns because I couldnt get through a second sidewalk on the run because of many roots from a 100 foot tree and the location of our swimming pool. I am still not %100 sure if it will be 360 degrees but it will be close.

Last Last question (for today ) I have been also trying to figure out whether I need to add a grounding rod or run a ground from the panel. different people seem to say different things. (it will be a 60 amps sent to the sub btw).

You'll need to include a #10 ground and maintain isolated ground and neutral bars at the subpanel if you are on '08 code. Also

good info from nec code, I was wondering if I had to add a ground rod but sounds like the #10 wire should cover it.

great info thanks!
 
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Old 04-23-08, 01:27 PM
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Although your local code may have different requirements, according to the NEC if you are running to a detached building then a ground rod at the sub panel IS required.

This is in addition to the equipment grounding conductor pulled from the source (service) panel.

If you can dig your trench with a wide enough arc you may lay the conduit within and not count the arc as a bend.
 
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Old 04-23-08, 01:45 PM
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Originally Posted by Tim T. View Post
I couldnt get through a second sidewalk on the run because of many roots from a 100 foot tree and the location of our swimming pool. I am still not %100 sure if it will be 360 degrees but it will be close.
Did you try to use a garden hose drill? You can take a short piece of conduit and run a garden hose through it to make an improvised hydraulic drill to get under sidewalks.

figure out whether I need to add a grounding rod or run a ground from the panel.
The ground rod is required; its function is independent of the #10 ground wire which may be required. Personally, I believe the fourth wire should always be installed but there are certain situations in NEC05 and prior where three-wire is permitted.
 
 

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