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amakarevic 06-28-2011 04:13 PM

terminating conduit connection between house and detached shed
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i was wondering how to terminate the conduit connection between my basement and my detached shed. i have 50A going in 1" conduit (3 gauge 6 wires and 1 gauge 8 for ground) and i have security wire going in a 0.5" conduit (i will have ADT cause i live in a somewhat high crime area). as can be seen in the pictures, i have run the wires already (about 30 ft distance under ground) and i need to attach some sort of boxes on each end but i am not sure which kind and how it's done. once the boxes are installed, i will run regular cable from the box to the subpanel for power and to the security panel for ADT. but i need to know which kind of boxes and where to put the (attached to studs maybe?).

any input would be appreciated.


SD515 06-28-2011 07:47 PM

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With a ‘hot-box’ or heat-blanket, it’d be pretty easy to make an off-set that would look good in the shed, but they’re not cheap.

In the shed….2-90’s or 2-45’s, (45’s would pull easier) that head towards the OSB, then would enter the bottom of a 6X6 PVC pull box, which could be mounted to a piece of plywood that gets attached to the 2 studs behind the conduits, straddling the open bay. Set it so you can get a clamp on the pipe, but also get the locknut on too (for the male adaptors you'll need at the ends of the pipe going into the boxes) A minerallac clamp should work well. See picture.

In the house, straight into the side of a 6X6, mounted to a piece of plywood mounted on the stud? Can’t tell the clearance though. Might be better to use a 90 that goes straight up the stud into the bottom of a 6X6 pull box a couple feet up so you can get the pipe in and also get a clamp on the pipe. Just ideas.

Pull the wires back out, build the conduit system and mount the boxes first, then pull the wire back in.

amakarevic 06-29-2011 04:15 PM

thanks. one more question: i noticed that 6x6 and 4x4 boxes come without inlet holes. is the user expected to drill them himself?

SD515 06-29-2011 06:29 PM

Yes. A vari-bit or a hole saw works well. You can get reducing washers if you overdrill, but take your time and check as you go. Make sure not to drill too far back so the locknut will spin.

amakarevic 06-29-2011 06:31 PM

but do i put the conduit pipe through the drilled hole or do i put some sort of fitting? and why the heck did they make it that way, i mean why didn't they predrill holes?

amakarevic 06-29-2011 06:48 PM

i mean, i don't see how the locknut in the picture secures the pipe or fitting to the box, i only see that it goes around the pipe.

SD515 06-29-2011 07:49 PM

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The picture posted earlier is a minerallac. They’re used instead of a strap type clamp. With a strap, the pipe has to lay against the surface it’s mounted to. Then an off-set is needed to kick the pipe away from the surface as it enters the box, allowing the locknut room to spin on the pipe fitting.

A minerallac keeps the pipe away from the surface the same distance required to enter a box that has standard knockouts, so you don’t need to bend an off-set in the pipe. One reason they work nice with PVC pipe.

PVC pullboxes don’t have knockouts so 1) you drill them where you need them 2) if they have a gasketed cover, they can be used for exterior applications, so you don’t want extra holes, etc. to let water in. Metal pull boxes do come with or without knockouts. If you were to use a box that has knockouts, then you have to get the pipe to line up with them. Without knockouts, you can enter box more freely where you wish.

Here is a picture of a male adaptor you’ll need on the end of the pipe where it enters the box. It’s glued to the end of the pipe, the threads go in the box, and then the locknut to hold it to the box.

If you pop into a local supermarket or open commercial building, you can see how some pipe is run and goes into j-boxes, etc. Look how it’s done and you can get some ideas and such.

amakarevic 06-29-2011 07:53 PM

so are you saying there is a PVC female locknut that goes onto the threaded end (male) of this adapter inside the box? that would actually make sense. i still don't understand where the metal one fits into the whole structure, i.e. whether it is just an alternative option

thanks a lot :thumbsup:

SD515 06-29-2011 08:13 PM

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Not a PVC female adaptor. A locknut like this picture. They come in stamped steel or cast metal. Either will work. Forgot to mention you have to get them separately, they don’t come on PVC male adaptors, like they do on EMT connectors.

I mentioned the metal pullbox as a comparison, to discuss the knockouts, because PVC’s don’t come with KO’s. You asked why PVC box don’t come with holes. That’s all.

And you're welcome :thumbsup:

SD515 06-29-2011 08:17 PM

And yes, a metal pullbox can be used as an alternative, but then you have to bond it (ground it) to your #8 EGC wire that goes in it. Easier to use a PVC box.

amakarevic 06-29-2011 09:41 PM

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OK, it makes sense. i just came back from HD and got female adapters, which i will be returning. the one on the left in the picture attached. i thought the male would go inside the box and the female threaded onto it on the outside and then the conduit into it.

but do i need to secure the cable/wire that goes into this kind of assembly so that it can't be pulled?

also, what should i do for the Romex coming into or out of the box, which is gonna be on the inside part of both the shed and the house? what kind of connector should i use for that?


SD515 06-30-2011 08:51 PM

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Just FYI, a common use for the female adaptor is when changing from PVC to another type of conduit, EMT for example. Glue the FA onto the PVC pipe, screw in a EMT connector, and start piping the EMT.

Back to the questions at hand. You don’t secure the wires in the conduit. First, pull the wires out. Get the boxes set and have the conduit run between boxes all done before you pull the wires in. The conduit will support the wires.

I suggest you start with the house portion first…looks easier to do, and will give you some practice before tackling the shed. Working with electrical PVC is pretty much the same as working with plumbing PVC, if you done that before. Start with the pipe coming into the house and work your way up the stud. Attach the box last, after the rest of the pipe is cut to length, glued together, etc. It’ll go easier than mounting the box, then trying to get the pipe in. Check that things will work as desired before gluing, but be aware if you test fit the pieces, they won’t go on all the way and can get bound up when the parts are dry. They’ll go in all the way when they’re wet with glue, but you only have a couple seconds before the glue sets. Just like plumbing PVC.

When that’s done and you’re ready for the cable, you’ll drill a hole and use a cable connector something like these…..
I like the type with the locknut better personally, but to each their own...:) Get the size appropriate for the cable you'll be using.

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