Locating short in power line to well

   / Locating short in power line to well #1  

Pilot

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Oregon
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JD 770, Yanmar 180D, JD 420 (not running), had a Kubota B6200
Woke up Monday with no water pressure. Well guy came out, checked things over, replaced a capacitor, a relay and another component in the control box and ran a temporary power line to the well, saying I had a break or short in the line.

Called 3 locator services, they all charged the same & picked one, knowing nothing about any of them other than their charges.

Wasn't impressed with the guy, but he located the line, then went over it with another piece of equipment and marked where it showed the problem. Said if there is another break, he can't find it until this one is fixed. $195.

Only the problem wasn't there. The line was 3 ft. down and I found 3 spots where the white outer insulation was damaged and two of those places showed damage to the insulation on the black wire, but no copper exposed.

Now I have the wire up in the air so there's no possibility of a ground from the black wires to the ground (wet soil) in case I'm just not seeing a pathway.

Hooked up the ohm meter at the garage end of the line and found a short between the black and white wires, 2.8 ohms. But in those damaged spots, the white wire was not damaged or even visible (just to be sure there's no confusion, the outer insulation over the 4 wires is white and one of the inner wires also has white insulation; and that's not exposed).

So I check resistance between white and black wires at the well end and get 3.2 ohms, vs. 2.8 at the garage end. Now I'm limiting out on my electrical knowledge, but this suggests to me the short is closer to the garage than the well--more resistance at the well due to a longer path. The locator guy's spot was only about 15% of the way from the well to the garage--maybe less. Am I right that the break should be closer to the garage?

So, what now?

If I call the locator guy back, he will say he can't check it because I haven't fixed the non-existent fault he found before, but there's nothing to fix.

I watched him work. The locator device looked pretty simple, on an A frame with a meter in the crosspiece. He stuck each leg in the ground, the thing thought for 3 seconds then the needle pointed left or right, indicating the fault was in one direction or the other. Then it was just a matter of getting it centered over the fault, at which point the needle was centered.

Where he claimed the problem was, the wire is almost 3 ft. deep. Could it be that it was too deep for his equipment to get a signal, causing a false indication?

If I call him back, he wants to charge me again, although he said he would "give me a break on the price". Yeah, he should return for free, but the way he worked, I doubt he will do that, and I might be better off calling someone else, but that would be another $195 the way these guys charge.

So, what now? Any ideas?
 
   / Locating short in power line to well #2  
I am a Canadian electrician so I do not want to get too deep intp your NEC. Replace the feeder to the well. Install it in 3/4" or 1" Ridgid PVC conduit buried 2' down. Use 90 degree bends and LBs to form the work. Use the same grade of cable that the well company will supply to you.Pull the conductors in with poly string and plain water as a bit of a lube. In this way if the soil / rodents/ stones ever damage the conductors again you pull them out and pull in fresh conductors.
Thats how I did mine.
Craig Clayton
 
   / Locating short in power line to well #3  
I would have never wasted my time I would have a new trench dug by now and ready to lay new wire. Conduit is cheap i would put it in conduit.
 
   / Locating short in power line to well #4  
Copper wire has specific resistance per foot. With that said you will need a special meter to accurately measure resistance that low. Even a good digital meter won't work. What you need is nulling meter that will do what is called 4 wire resistance.
If you know the wire size 12, 14 etc, you can calculate the exact resistance per foot and double it for your problem. The trouble is that you don't know how 'good' a short you have. If you had a dead short you could calculate the resistance if it is only shorted in one place but the short may not be 100% shorted.
The other question you have to ask is why it broke down and shorted in the firt place. Is the whole line about to fail and when you fix one problem will another one show up? If it was my well I would probably run a new line. Code here is 18" to two feet. How long is the run? Can you find the mid point and save half of a full run?



Sorry for all the questions but there is no easy solution.

Rob
 
   / Locating short in power line to well #5  
Did directional boring for gas and electric company. Would follow Craig's recomendation use a liner and run new wire. A trick we used was to tie fish line on a small piece of cloth. The cloth was fed into the conduit and the fish line was ranout x number of feet. A shot of air from a compressor would blow the cloth trough the line. Masonary line followed the fish line, which pulled the cable. Have done the dig patch and repair followed by dig patch and repair. Ground was frozen and ended up leaving new cable above ground until spring.
 
   / Locating short in power line to well #6  
An instrument called a TDR can locate a short to within 1 foot, buyt this is a quite expensive instrument and not available to most individuals. If you know any telco line service guys, ask them if they can help in their spare time.

paul
 
   / Locating short in power line to well #7  
Have you disconnected power from the power source and disconnected the leads to everything on the other end? Then check with your ohm meter for a short. Feedback with a shorted motor will give you the same results. All in all, what I am saying is the wire may not be your problem at all. Disconnecting both ends of the wire and then checking will tell you if problem is wire or further down the line. From what your describing it sounds like you very easily might have problems twoard the motor end.
 
   / Locating short in power line to well
  • Thread Starter
#8  
Thanks for your responses.

I would replace the wire and go with conduit, but the first 50 feet is under concrete and I really don't want to tear up my garage floor and a concrete pad outside the garage. After the concrete, I have another 60 feet to go, just thru soil. The line is 2-3 feet deep, depending on location. So running a new line from the garage has problems. But:

Another idea: My barn has separate power and the panel is only 60 feet or so from the well, with no concrete and no obstacles. I would need some place for the pressure switch, so that might mean some sort of enclosure, probably by the well.

Yes, when I checked with my ohm meter the wire was disconnected on both ends.

The wire is 10 gauge. I could probably borrow the kind of meter Rob-D mentioned. Don't know if it is a dead short, but I suspect it is because it killed the capacitor and relay.

An engineer friend loaned me a clamp meter, so tomorrow I'll put some current thru the wires and see if it flows beyond each of the suspect spots. Worth a try.

Question: My friend the engineer (not electrical, but he knows a lot of stuff) says the locator device works by sending a radio frequency signal down the wire and sensing it. So how deep will these sense a problem? The probes were closer than the depth of the wire, and I am wondering if the thing lost the signal and gave a false indication because the depth may have been greater than a wave length?
 
   / Locating short in power line to well #9  
Have you disconnected power from the power source and disconnected the leads to everything on the other end? Then check with your ohm meter for a short. Feedback with a shorted motor will give you the same results. All in all, what I am saying is the wire may not be your problem at all. Disconnecting both ends of the wire and then checking will tell you if problem is wire or further down the line. From what your describing it sounds like you very easily might have problems twoard the motor end.

Agreed. Unhook BOTH ends before trying to do a resistance reading. And dont just do from white wire to black. If it has a ground, check both hot and neurtal aginst it as well.

If you left it hooked up to the motor, this could give you a false reading, depending on what type of motor it is and how it is wired. ISOLATE the wiring before making any rash decisions.

And if the wire is faulted, rent a trencher for a day and lay new wire in conduit. Not sure how long your run is so $$$ of material???? but you should be able to rent a trencher for the cost of having the locator guy come back out again.
 
   / Locating short in power line to well #10  
Relocating your pressure switch would also mean relocating your tank also wouldn't it? Or possibly installing a contactor that would be triggered by your pressure swicth, but that would require wire from your tank location out to your barn.

Another option may be to run conduit overhead through your garage, out the back/side, down to underground conduit out to the well. By running overhead you would avoid having to be worried about what's under the slab. Using conduit means that you would should never have to worry about digging your well power feed up again. Finding an alternate path for rerunning power to the well appears to be the surest and simplest solution.
 
 
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