Garage subpanel wiring

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  #1  
Old 10-14-13, 12:08 PM
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Garage subpanel wiring

I just recently removed the mess of wiring that the previous owner of our house ran out to the garage (detached and set back about 20 feet off to the right of the house). He had run 6/2 romex NM-B through a plumbing PVC tube only about 1" under the back patio slab to a free standing subpanel that wasn't attached anywhere and sat on a garage shelf...

As it was routed under grass and L'd toward the garage there was about 40' of extra wire run. Now that I've deep six'd all that, I want to start fresh.

I'm looking to either do a straight shot under the slab (garage overlaps line of sight with the edge of the house by about 4') or will do a similar L routing but less distance than the PO.

If you're running conduit under a large piece of slab are there any methods to employ that will help know exactly what portion of my garage floor I'll need to open up with close certainty? As I have to go down 18"+ according to code, I'd like to minimize how much of my floor I need to break apart. There is no soil around the back of the house or any of the garage.

Am I better off running galvanized conduit under a slab so that I only have to go 6"+ down under?

Any suggestions are appreciated. Thanks.
 
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Old 10-14-13, 06:33 PM
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I'm looking to either do a straight shot under the slab (garage overlaps line of sight with the edge of the house by about 4') or will do a similar L routing but less distance than the PO.
How were you planning on running conduit under a concrete slab? Normally slabs get sawcut and excavated and repoured after conduit is installed, is that what you had in mind?

If you're running conduit under a large piece of slab are there any methods to employ that will help know exactly what portion of my garage floor I'll need to open up with close certainty?
I'd turn the conduit up outside the garage and 90 degree through the wall with an LB condulet fitting rather than breaking up the concrete floor.

There is no soil around the back of the house or any of the garage.
I might be missing something here. Is the slab continuous from the house to the garage?
 
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Old 10-14-13, 08:41 PM
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Hi CasualJoe, Rather thank break up the slab was going to drill through the basement cinder block and use the jet method or sledgehammer / shaft method. This would eliminate the need to break up the concrete or excavate and move the slab. It just comes down to originating location. Yes slab is continuous from house to garage with it also wrapping around and down the side of the garage. There are two expansion joints but there is also one area that sits in line with the garage facade that stone work is dressed in the concrete. I could also potentially pull those temporarily to assist with running the conduit.
 
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Old 10-14-13, 09:12 PM
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You are drilling a hole in the basement and driving in a piece of pipe. Using that method you'd have to drive a larger piece of pipe as a sleeve. You would not need to stay down any particular depth under the cement as the conduit is completely protected by the cement as long as the cement is 4" thick or thicker.

How far do you have to go between the basement and the garage.... 4' or 20' ?
Not going to be an easy job.

Here's another thread from the forums on this topic.
http://www.doityourself.com/forum/el...der-slabs.html
 
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Old 10-15-13, 03:54 PM
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Thanks for the responses again, here is a diagram to help illustrate what I am up against. The darker grey is newer concrete (6 yrs old). The lighter is old concrete (apps 20 yrs) There is a set of bilco doors at the back of the house, whose right edge almost line up with the expansion joint. The little dark line is a set of stones that separate the bigger slabs from the pathway along the side of the garage.

The (believed) original wiring path is in yellow. The new proposed one is in orange. However I think I may need to meet somewhere in the middle and still circle back towards the grass side slightly.

One of you mentioned that if run under a slab 4" or thicker, placing under slab is acceptable. How can I tell the routing of the tubing under the slab? I am estimating its taking the path in yellow however it could elbow twice and all be under the slab I'd imagine....

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Last edited by PJmax; 10-15-13 at 07:20 PM. Reason: Removed duplicate picture
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Old 10-15-13, 07:28 PM
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For some reason you had a duplicate picture in your post.

Have you ever attempted driving a pipe horizontally like this before ? 22' is an awfully long way to drive it. If you hit a rock you could veer off your mark.

The other thing is you'll need a way to couple your pipes together due to the length. The coupler will make the process harder.
 
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Old 10-15-13, 07:39 PM
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I've never done this no. My father's done it a number of times though. My soil is very sandy though with no rock, so maybe I'll have decent luck. if the initial plan doesn't work, then I could L it like the old owner had done but within code/spec. The area of grass immediately next to a potential point of entry, I already dug up the corner and it only took less than 1/2 hr to dig 18" down....
 
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