How do I to test underground wire?

[dcyrilc]

I'm an electrician and can say the advice you've gotten so far is accurate. b2910 posted that an ohmeter may not provide enough voltage to detect a problem and that is very true. If it does indicate continuity to ground there's no doubt you have a problem or if you don't have continuity from one end to the other. What you really need is a friend or electrician with a megger that will test to ground and between conductors at hundreds of volts.

You need to test it with an electrical insulation tester commonly referred to as a Megger(brand name). It uses a high voltage and measures for current leakage through the insulation to ground Megger. There are lots of different brands just make sure that it is a voltage tester that test at at least 2 times the normal voltage. Disconnect the motor before testing.

You guys both beat me to it. The best means is to megger it. Our megger tests at 1,000 volts. Ask if your friend has one or has access to one. It really is the only accurate portable tester I'm aware of.

 

[ayelvington]

Have to throw my vote in for the Megger... This kind of work was my stock and trade for a long time.

 

[grsthegreat]

another funny thing about direct burial wire.....if you nick the sheathing and expose the aluminum wire.....it still may work, but the wire WILL rot away in a year or so.

Seen it more times than i can count. even a large rock can nick it enough to rot the wires.

 

[Iowachild]

another funny thing about direct burial wire.....if you nick the sheathing and expose the aluminum wire.....it still may work, but the wire WILL rot away in a year or so.

Seen it more times than i can count. even a large rock can nick it enough to rot the wires.

Which is why I always put underground runs in PVC conduit. Cheap insurance!:thumbsup:

 

[grsthegreat]

Which is why I always put underground runs in PVC conduit. Cheap insurance!:thumbsup:

yup..same here. but sometimes its next to impossible to convince a client to do it.u

 

[dcyrilc]

yup..same here. but sometimes its next to impossible to convince a client to do it.u

Same here, but I hate aluminum so I always run copper even with the higher expense.

 

[grsthegreat]

Same here, but I hate aluminum so I always run copper even with the higher expense.

YOU MUST BE RICH HEHE:laughing: :laughing:

 

[rd_macgregor]

Electric fence energizer might also detect insulation flaws...the underground snapping sound tells me that a leak in my buried supply wire is the reason the fence isn't working right!
I'm not sure if 5k volts or so would damage intact insulation in a regular 220V wire, though.
Its a great time to have an electrician friend!
BOB

 

[dcyrilc]

YOU MUST BE RICH HEHE:laughing: :laughing:

I wish.:laughing::laughing:

It just takes me a lot longer to save up for electrical projects. Sometimes I miss being an electrical foreman. I used to be responsible for getting rid of all the old scrap wire and such. A lot of that was quite reusable and went home with me rather than to the scrap yard. Luckily though, after nearly 30 years with the same company and being well known at the supply house, I can still buy direct from the supply house at a wholesale price. That does help greatly.

 

[Illini22]

We use a dynatel to find faulted secondaries. Of course if you know where the damage occurs you know where to dig. As one poster wrote, aluminum wire will corrode, it will turn to white powder. Depending on soil conditions it could be weeks or years. Definatly expose your cable wipe it down and look for nicks. If the able isn't damaged to bad you can Use a split shrink tube. You but it around the damaged but not broken cable and then put the zipper on it to hold it together and then shrink it. If you have to splice then you can use a regular shrink tube with the splice. This is a minor repair. Be glad it's not in pipe or you would be replacing you service entrance and the utilitys transformer when the backhoe broke thru the PVC and yanked on the cable, in addition to replacing all the wire. Now you have a minor repair, some split shrinks or at most 6 splices, 6 shrink tubes and a few feet of wire, much cheaper. Ok I'm ready to get roasted!