Resistance test on cores of buried cable (Ed.)

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Okay, so here is my situation. I am pulling a 20 amp circuit from my garage, 150' to pillars at the end of my driveway. A buddy had 4 runs of 150' of 8 gauge wire he had pulled from underground, because he needed more amperage to his workshop. Like an idiot, because I was looking at today's problem, not tomorrow's, I ran 1.25" PVC for the run, 24" underground (per code here), pulled three wires through, and buried it. Unfortunately, work (real job) interfered, and it was 2 weeks before I could get back to the project and run my connections. Because I am slow and an amateur, it didn't occur to me to check continuity on my lines until this morning. Still haven't attached any of the 3 wires that are underground, but used 4th wire connected to each in sequence to check resistance. Each wire showed ~ 0.1 ohm resistance over the full run (300') which should be about right, as I should be getting 0.18 ohms resistance for this length of 8 gauge. The problem is that I accidentally tested known good to one of the unconnected wires, and instead of OL (open line), my ohm meter showed 2 M ohms resistance... from my reading and very basic university level physics, I get that I may show some resistance because of magnetic induction in the unconnected wire, but, before I connect these wire to the home power, I wanted to ask some experts if this is indicative of a short underground, or if this is perfectly normal.

In order to anticipate the info you may need, I am using a 400a 600V Kobalt DT-9180A digital multi-meter and it is multi-strand copper wire 8 gauge, run through 1.25" PVC. Any other info you may need to help me out, let me know. As of now, I still haven't attached either end of the wires, either to the house power or to a plug at the gate pillar.

Best regards,
Dan
 
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Ooops, while to me it is self-evident (simply because I grew up with it) I suppose I should mention that this is a 110V line, not 220/240... not sure if this needed saying or if it is relevant at this time, but wanted to give all data I could think of.
 
OL is/wasn't ever "open line", it's just out of range for the meter to measure, more like over load.

Any hint of water or of course you touching something, might give a reading of 2M ohm.
You do have a long aerial there so could be picking something up which is making the meter show a reading.
Only answer really is to get an insulation tester (aka "Megger" if you're old enough) which tests with a lot of volts instead of the very low voltage and very sensitive resistance meter.
 
Okay, so here is my situation. I am pulling a 20 amp circuit from my garage, 150' to pillars at the end of my driveway. A buddy had 4 runs of 150' of 8 gauge wire he had pulled from underground, because he needed more amperage to his workshop. Like an idiot, because I was looking at today's problem, not tomorrow's, I ran 1.25" PVC for the run, 24" underground (per code here), pulled three wires through, and buried it. Unfortunately, work (real job) interfered, and it was 2 weeks before I could get back to the project and run my connections. Because I am slow and an amateur, it didn't occur to me to check continuity on my lines until this morning. Still haven't attached any of the 3 wires that are underground, but used 4th wire connected to each in sequence to check resistance. Each wire showed ~ 0.1 ohm resistance over the full run (300') which should be about right, as I should be getting 0.18 ohms resistance for this length of 8 gauge. The problem is that I accidentally tested known good to one of the unconnected wires, and instead of OL (open line), my ohm meter showed 2 M ohms resistance... from my reading and very basic university level physics, I get that I may show some resistance because of magnetic induction in the unconnected wire, but, before I connect these wire to the home power, I wanted to ask some experts if this is indicative of a short underground, or if this is perfectly normal.

In order to anticipate the info you may need, I am using a 400a 600V Kobalt DT-9180A digital multi-meter and it is multi-strand copper wire 8 gauge, run through 1.25" PVC. Any other info you may need to help me out, let me know. As of now, I still haven't attached either end of the wires, either to the house power or to a plug at the gate pillar.

Best regards,
Dan
While I really do not have much of a clue about that which you are asking,
I suggest that this question would be better posted on the North American site ofv
 
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If the cable is:

undamaged and

has nothing connected to either end and

the conductors are well isolated from each other

then I would expect a very very much higher insulation resistance reading.
 
However, connecting a DMM to 150 feet of wire could cause all sorts of strange readings, mainly from capacitive coupling I suspect. As others have said, you really need a proper insulation resistance tester with 250 or 500 V DC test voltage. Finding one in the US will be tricky though, they have nothing like the testing and inspection we‘re used to. I don’t thin most electricians own anything beyond a plug-in socket tester and a multimeter.
 
The resistance of a length of a conductor can be measured by passing a known current through the conductor and meauring the voltage created by the current. Then calculate R = V / I ( I being the test current ),
R from A and V.jpg


The test current should be about an Amp to swamp any induced current and the Voltmeter should be protected against over voltage.
 
You can test the resistance of each conductor (which was the initial question) but not insulation resistance between two conductors. That requires a significant DC voltage.
 
At 4.5 volt the meter is no good to test insulation, you need at least 100 volts, in UK our meters have 250, 500, and 1000 volt DC options, never seen a meter designed for 120 volts, but since measuring with DC there should be very little background leakage. Using the clamp-on function once powered up, yes since 60 Hz there will be some loses.

So in my house UK the insulation resistance is over 1MΩ and 230/1000000 = 0.23 mA, but the clamp meter shows 8 mA because it is AC at 50 Hz. This is why we have to measure the earth leakage, and not assume if insulation resistance is OK the earth leakage will be also OK, we should not have more than 1/3 of the RCD rating of background leakage so 9 mA with our 30 mA trips. Although the regulations do not specify this.

I suggest that this question would be better posted on the North American site ofv
That is good advice, as I for one have no idea what 8 gauge is. Nor do I need to know.
 
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