Electronics > Repair
Finding fault location for broken power cables in walls
Gregg:
A neighbor completely rebuilt his garage and wired it with romex per code. He called me in a panic because the electrical inspector was coming later and a breaker kept tripping for unknown reasons. The stucco installers had used long staples to fasten the chicken-wire for the exterior stucco reinforcing and had pierced the romex causing a short. Of course drywall was installed on the inner walls. I located the fault with an Amprobe CT-326 tracer meant for finding circuit breakers on live circuits. Unfortunately this model is no longer made and some of the replacements by Amprobe are not as good at pinpointing faults.
https://www.amprobe.com/product/ct-326-c/
calzap:
Let me repeat that injecting RF won’t work for tracing because it can easily jump from a wire to an adjacent wire. The broken cable is bundled with other cables along its entire length. When RF is injected, I can trace the broken cable from one end to the other. But if I back-feed power into one end, there’s none at the other end.
Here’s what’s going to happen. I’ll back-feed into the ends one at a time. I’ll use the 60 Hz detector I use for tracing underground cables (made by Radiodetection). Work from each end and see if there is a common weak or vanishing point. If no success with that, I’ll rewire from the attic. Rewiring from the attic might be simpler and certainly cleaner than repairing the break in the wall … no drywall to cut and fix. It will take two boxes to fix it either way. In the attic, they’ll be unseen. In the wall, there will have to be blank covers over the two boxes.
Although it might be more satisfying to locate and repair the break. At some point, practicality must intervene.
Mike
bostonman:
--- Quote ---Haven’t been in the attic yet, so it may be more complex than described above.
--- End quote ---
Not sure where you're located or how sealed the house is (twenty-five years isn't that old), but, if you're in a warm climate, consider that you may have bees up there and need a quick escape before you climb through some small entrance.
Around here many houses have tiny doors in the ceiling of closets, so once you crawl through, you're kind of stuck up there. I along with many other houses installed a pull down attic door.
calzap:
--- Quote from: bostonman on December 06, 2024, 02:08:38 am ---
--- Quote ---Haven’t been in the attic yet, so it may be more complex than described above.
--- End quote ---
Not sure where you're located or how sealed the house is (twenty-five years isn't that old), but, if you're in a warm climate, consider that you may have bees up there and need a quick escape before you climb through some small entrance.
Around here many houses have tiny doors in the ceiling of closets, so once you crawl through, you're kind of stuck up there. I along with many other houses installed a pull down attic door.
--- End quote ---
There's a metal hatch to the attic in the garage ceiling very close to wall with the dead outlets. Main concern is I might not have easy access to the top of the wall in the attic because it's a fire wall ... wall between the garage and the rest of the house. May be OK because usual method is to double-thick the drywall on wall and ceiling and not have anything special above garage ceiling. And that's probably why the attic hatch is metal. Will probably have peek next week.
Mike
Poroit:
G'day Mike,
If you find the location of the Break/Cut, I imagine you will still need to cut a hole at least 300 x 300mm to be large enough to access the cut ends.
There may not be enough slack in the cable for a simple butt joint. You may need to insert a short length between the two cuts ends.
Wago are good for that type of work.
https://www.wago.com/au/electrical-interconnections/discover-installation-terminal-blocks-and-connectors/221#durchgangsverbinder
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