Running wire to freestanding building


A friend was complaining last night about how major repairs often come in clusters, when you can least afford them. The latest: It seems the AC wire to her freestanding garage has rotted away. The installation's probaby 50 years old. The BX cable comes out of the ground right at the garage, and there's no indication of it having been run through any sort of protective pipe. It enters the house through concrete block, below ground level. The garage is only 18 feet from the house, and although the ground is very easy to dig, the wire has to pass below a sidewalk to reach the house.
The sidewalk is adding to her nightmare because she's thinking that removing any soil at all (to run the new wire) will cause some pavement to collapse, so she'll end up needing masonry work, too.
Anyone know what's really involved in replacing a wire like this? In a perfect world, there would be no sidewalk or other annoyances, I'd install the wire in the appropriate pipe, there'd be birds and flowers and everybody would live happily every after with free beer. But...ya know....
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JoeSpareBedroom wrote:

why does she need air conditioning in the garage?
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Ummm....alternating current. It's all the rage these days.
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It's probably not a BX cable, but a direct burial cable with lead sheath over the conductors. Easiest thing to do would possibly be dig a narrow trench and bury a pvc pipe

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On Mon, 30 Oct 2006 12:42:42 +0000, JoeSpareBedroom wrote:

Water jet underneath the sidewalk using a piece of plastic conduit. Dig a shallow hole on each side of the walk. Shove the conduit from one hole to the other with water running, under pressure, through it. Easy to do where I'm at in Fla. with the whole state being one big sandbar. Worth a try where you are in NY.
Once through, cut off the 3/4" male pipe threaded nipple you added to connect the hose to.
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It's a sidewalk.. that's what, 24"? Dig a pit on either side, and sledgehammer a chunk of 3" blackpipe across. Then run 2" PVC conduit through the pipe. Don't use 90degree bends, either use sweeps, or use 45 degree bends, and cross the sidewalk at an angle.
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Goedjn wrote:

More like 36" if it's ADA compliant.
Given that the total run is reported to be 18' through easy soil I'd be inclined to pipe jack the full length from inside the basement and leave the digging to just a minimal pit to install the sweep at the garage end.
Pete C.
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What do you mean by "pipe jack"?
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JoeSpareBedroom wrote:

More-or-less literally just that, you work from an access pit, or in this case the basement and literally push the pipe into place through the ground using a hydraulic jack.
They use a version of this on a large scale for big sewer pipes where they work inside the pipe digging at the front and pushing the pipe along as they go, but for your case just putting a drive point on the end of the conduit should be fine.
Since we're only talking about two sections of conduit I'd probably go with rigid galvanized for it's resistance to flexing during the push. You might be ok with sch. 80 PVC as well.
Basically you just drill a hole in the foundation wall facing the correct direction and then start pushing the conduit in. Find a solid point to brace the jack on and use varying lengths of material (say 4x4) between the jack and the conduit as you push. For 1.5" - 2" conduit it shouldn't take that much force if the soil is easy to dig as you indicate.
Pete C.
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JoeSpareBedroom wrote:

Is the location where the feed enters the house (basement?) accessible? Is it a straight line (not necessarily right angle) to the garage? If so then for such a short length in easy to dig soil I'd consider a pipe jacking operation with rigid conduit like sch. 80 PVC.
Pete C.
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You can use a LARGE Wood bit like a electricians bit with extensions and drill underground as long as you arent in a real rocky area
I used my friends setup on a electric drill just to try it went 15 feet in no time at all. hard on bit but can save oodles of hard work
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Not sure why nobody's suggested a direct-burial wire (UF-B) with no conduit. Seems like by far the easiest solution. Just water-jet under the sidewalk as suggested. Make sure you're low enough to meet code.
-Tim
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I'm aware it can be done without conduit, but this wire passes beneath two flower beds. Enough said?
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Not really. How deep do you dig your flowers? Code requires unprotected UF-B to be something like 24" (don't quote me). If you're digging that deep for flowers, you're planting something pretty hefty!
Just for safety, you could put a conduit around that portion, or a pressure-treated board over it, or...
Or you can run the whole thing in conduit -- but it will be much more work.
-Tim
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