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Old 03-15-2012, 05:00 PM   #16
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Conduit questions in shed wiring


Hand trenching is not what I would call minor work. If you have any substantial sized rocks be prepared for a wild ride and lots of cursing. No rocks and it should be a cake walk.


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Old 03-15-2012, 07:41 PM   #17
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Conduit questions in shed wiring


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Hand trenching is not what I would call minor work. If you have any substantial sized rocks be prepared for a wild ride and lots of cursing. No rocks and it should be a cake walk.
Are you referring to operating the power trencher I'm thinking of renting? If anyone wants to share any safety tips etc, please do In the digging I've done so far, I haven't really encountered any rocks bigger than 2-3 inches, so it's been surprisingly easy in that regard. But I've only gotten about 5" down.

I was curious how the trencher will work -- where does it eject the dirt it digs out? Will it be flinging it backwards at my legs? Does it spit it out in a nice neat line alongside the trench, ready to be backfilled after the pipe/conduit is laid? That'd be nice.

Also, do those trenchers have powered drive wheels, by any chance? (Looks like I'll be getting something equivalent to a Ditch Witch 1030). And are they able to be "driven" with the blade up, so as to [I]not[/I dig a trench? I ask because there's a slight downhill slope to get into my yard, and I'd be nervous about pushing an 800+ lb machine up a hill when I'm done It's listed as a "walk-behind" machine, so I assume that means it is self powered, but I just thought I'd ask.

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Old 03-15-2012, 08:11 PM   #18
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Conduit questions in shed wiring


2 or 3" rocks are fine. When they get larger they make the machine hop all over the place because they are not meant to cut rock, but rather displace them out of the trench along with the soil. I rented a fairly large stand-on machine with carbide rock teeth and my rocky soil put it on its knees. I stopped using it and called for a return pickup after about 3 minutes of use.

You will like the way a trencher grinds the soil up into a fine powder that is easy to backfill with. Most have little augers or deflectors that will place the soil along the side of the trench.

Yes, yours should be self propelled.
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Old 03-15-2012, 09:20 PM   #19
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Conduit questions in shed wiring


Thanks, zappa. It sounds like my soil should hopefully be OK for it, and it will be a much more pleasant experience than doing this all by hand.

I've run into a new question that I'd love everyone's input on. Based on all my reading here and elsewhere, I had initially decided to run #6/#10 THWN in 1.25" sch40 conduit. As I learned above, I need to have the wire in conduit all the way through the basement drop ceiling as well. I bought all the materials -- 95' of my four conductors, and 90' of conduit. Now I've started working on routing the conduit from the panel to the point at the external wall where I plan to have it exit the house, and I've realized that this is going to be very difficult. Getting the 1.25" conduit (with it's big sweeping 9" wide elbows) routed through and around all these floor joists and everything is really awkward, and I'm not even sure I'll be able to find a good route for it.

I'm now considering returning all this wire and most of my conduit, and running 6/3 NM from the panel to the exit point (about half of the run), and only there switching to the THWN in conduit. Now, this had been my plan to begin with, but I came across some comments in threads here advising people to avoid the splice and run the THWN the whole way, which is why I ended up planning for that. But given how difficult it's going to be, I'd really like to reconsider.

So I wanted to know exactly how big of a deal it is to have that splice from 6/3 NM to THWN. Is the main concern just that any splice introduces a point of higher resistance? Is there a better, if more difficult, way to make the splice to minimize the downside, like using some sort of permanent crimp-on couplers or solder or something? I obviously want to do this in the best way possible, but if it's doable to run the two different types of cable, it's going to make this job much more pleasant (not to mention cheaper, which would be very desirable for a project that has already grown a few hundred dollars over budget).

I've now gotta start reading more about feeder circuits using that bigger gauge NM, but can it be run in similar ways to the 12/2 I'm familiar with (i.e. through holes drilled in joists, etc)? Or does it have additional requirements over the smaller gauges for branch circuits?

Any thoughts on that plan? Thanks.

Dan
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Old 03-15-2012, 09:26 PM   #20
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Conduit questions in shed wiring


Thats the way I would have done the job.

6/3 to a box, make splices to the thwn and run in conduit to the shed.

The 6/3 runs like other romex.

Find some polaris taps and you will be fine.

Can you return cut wire?
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Old 03-15-2012, 09:29 PM   #21
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Conduit questions in shed wiring


Big blue wire nuts can join the #6s.

The 6-3 can run under the bottoms of the joists. You do not need to pull it through drilled holes.
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Old 03-15-2012, 09:36 PM   #22
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Ah, that's great to hear.

I guess we'll find out if they'll take it back. They did accept my 15' of #6 bare copper when I found I had to use #4 instead, but of course that's a much smaller-priced item. The Lowes employee who cut the THWN for me said that as long as it's still in like-new condition so it can be resold, it should be OK (i.e. once I cover it with lube and get it all dirty pulling it through conduit, it's mine to keep). But I guess I won't know for sure until I try. Assuming they take it, though, this change will both make the job much easier but it should also save me about $100 (nicely offsetting the cost of that trencher).

Dan
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Old 03-16-2012, 09:06 AM   #23
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As far as the splice, I know I have to do it in a junction box. If I've done the calculations right (for 6/3 coming in -- i.e. four 6 awg conductors -- and the THWN coming out -- i.e. three 6 awg conductors and a #10 conductor -- and four splices), I need 80 in^3 minimum volume, correct? This will be up above a drop ceiling and out of sight, so I'll probably use a bigger box than necessary just to make things more comfortable. I just want to be sure I know what "necessary" is

I'm actually a little uncertain about exactly how I should accomplish the transition from conduit to bare NM-B. I was planning on having the conduit run up the outside of the house to the sill at the top of the basement (about 7' above grade), put an LB at the top of that, and then have another short length of the 1.25" pvc conduit enter through a 1.75" hole I'll be drilling in the sill. I assumed it'd meet with a PVC junction box on the inside, where the splice would occur. But I believe I need a cable clamp on the 6/3 at both the junction box where the splice will occur and at the basement subpanel where it will feed from. I'm sure the subpanel clamp is self explanatory, but I'm not sure how I'll attach a cable clamp to the PVC junction box. Maybe I should use a regular junction box and use a male adapter to feed the PVC conduit into it, like I was going to do back at the subpanel? What's the standard way to make this transition?

Thanks for all the help, guys.

Dan
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Old 03-16-2012, 10:50 AM   #24
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Conduit questions in shed wiring


PVC boxes get drilled for the knockouts to install the clamps.

You are going to have 6 #6s and the #10 ground. A #6 is 5 cubic inches and the #10 is 2.5.
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Old 03-18-2012, 09:45 AM   #25
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Hi guys, another question. The chief inspector said that I wouldn't need sch80 in the places my conduit is exposed (against the house tucked in the corner by the deck post, and running up the side of the shed) because they won't be near a driveway or sidewalk, but I feel like I should install it anyway, because I could see SOMETHING hitting them someday. However, my local Lowes and Home Depot don't have any Schedule 80 PVC in 1.25" -- I think the smallest is something over 2", and maybe some 3/4" or something. Do I need to be looking at some other type of store? Or should I transition to one of the metallic types of conduit for those two runs? I know I'd need to bond it in that case, and I'd need to figure out how to do that, so I'd obviously prefer to find the Schedule 80 in the right size. What do you guys recommend? Thanks.

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Old 03-18-2012, 11:38 AM   #26
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deleted! double post.
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Old 03-18-2012, 11:42 AM   #27
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Don't incure the added cost since the inspector said it was ok not ot use it.
Stay with the sch 40.
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Old 03-18-2012, 11:52 AM   #28
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Conduit questions in shed wiring


I wouldn't use metal conduit. Schedule 40 is very very strong and unless you think it will be taking a direct hit from a heavy vehicle I wouldn't worry about it. If you feel that you "must" provide additional protection how about sleeving the above ground sch 40 with a slightly larger 40 or 80.

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Old 03-18-2012, 01:42 PM   #29
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Ahh, OK. Well, that makes things easier. Thanks, guys.

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