Voltage reduction?

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The electrician just left. He doesn't think it is the splice. He thinks there's a problem between the main panel and the sub at the workshop, underground, and recommends replacing the entire cable with copper. The current cables are aluminum. And we still don't know if it is direct buried or through a conduit. I'll have to talk to the contractor.

My concern is that there could still be a problem with the splice. He didn't test it or put a meter on it. He just disconnected it and pulled on the wire and pronounced it good. I may have to spend another $100 and get a second opinion. Ugh, this is my worst nightmare.
 
The splice is not likely the problem. It is was it would be loose. It would also probably look burnt or overheated.
 
So with this info turn off the breakers at both ends then at one end using jumper cords tie all 3 wires together then with an ohm meter read from the far end. Should get very close to the same reading between any 2 conductors.
 
I agree with Joe, the splice looked proper and in good working condition as long as the wires and crimps were sized accordingly.
 
Before I replaced all that wire I would start with cutting the power and then remove all the connections and clean the ends really good to get off any oxidation and also clean the holes in the termination. Then put it all back together with a good anti oxidation compound and torque the connections and see what you have.

To me it seems unlikely the wires would fail without some outside occurrence.

You could tie them together and also test them separate as suggested above. The insulation on each conductor should be rated at 600V so conductor to conductor should be over 1000V .

I would rule out oxidation first.
 
I don't quite understand the suggestion about tying them together and testing them seperately.
 
Raindem said:
I don't quite understand the suggestion about tying them together and testing them seperately.
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All readings should be within .2 ohm if one is higher it would show a bad connection like say that splice on the neutral.
 
I meant that I'm not sure how to conduct the test. Do you mean tie the 2 black cables and the white cable together at the main panel. Then go to the sub panel and check resistance through each pair? Black to black, black to white, etc?

I already tested resistance across the splice itself and got 2-4 ohms. However, my meter is a very old analog unit and probably not too accurate. I'm surprised the electrician didn't do this test but he seemed totally uninterested in that splice.
 
the object is to make a loop of two of the three wires and test it. Then make another loop using the third wire and test that. Then repeat again so that all wire combos have been tested with each other.
 
Ah, I see. The resistance between the black to black loop should be within .2 ohm of the restistance between the white to either black loop. If it is not, then the splice could be the problem. If it is, then it still points to a problem underground?
 
Your electrician should have at least conducted those tests for you before he recommended replacing the wire. Copper is a lot more expensive than aluminum, but also much more conductive, so he's "guessing" it's either a damaged underground wire or a voltage drop issue. The anomaly you're seeing at your workshop, seems to me, needed more testing from an electrician before the conclusion of replacement was addressed. I know you don't want to spend more money than needed, but the fact that he recommended replacing it with copper wire before doing any testing raises a red flag to me that he's looking for a nice payday. I would get a second opinion.
 
Kabris said:
Your electrician should have at least conducted those tests for you before he recommended replacing the wire. Copper is a lot more expensive than aluminum, but also much more conductive, so he's "guessing" it's either a damaged underground wire or a voltage drop issue. The anomaly you're seeing at your workshop, seems to me, needed more testing from an electrician before the conclusion of replacement was addressed. I know you don't want to spend more money than needed, but the fact that he recommended replacing it with copper wire before doing any testing raises a red flag to me that he's looking for a nice payday. I would get a second opinion.
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My thoughts exactly.
 
Currently doing an underground 200 amp service into my house. My building inspector said he has never seen it done in copper because of price. The price for the URD cable , 200 amp , aluminum, is under 2$ a foot.

If you went copper I believe the wire is much smaller and easier to bend/work with , which may be the reason the contractor is pushing it? I would do aluminum.
 
Will copper last longer? This house is only 7 years old. I don't want to have to be doing this again in 7 years.
 
Not significantly longer, you should never have to replace a wire every 7 years. Copper is just more conductive, can handle a larger load at the same gauge and its runs can be a bit longer when voltage drop is an issue. The only major flaw is that exposed aluminum can oxidize badly over time, so electricians use an anti oxidation compound when terminating. The major difference in price is what makes aluminum the preferred choice in residential feeder wires.
 
Copper can carry more current in a given conductor size but aluminum can carry more current per weight per foot. That makes it the wire of choice for many overhead runs. You simply have to use a larger conductor size is all and be back to the same capacity current wise. The disadvantage to copper is price and the disadvantage to aluminum is the oxidation problem.

Oxidation only happens where the aluminum is exposed to air and with the addition of things like salt can speed the process. If your wires are unbroken and underground oxidation shouldn’t be a problem inside the wires as the current travels inside the conductor not on the surface. Oxidation is a problem only at points of connection like under a cable screw connector or in a splice. They shouldn’t have put any splices anyplace that’s underground or not accessible. Again the oxidation happens on the surface and where two surfaces are being forced together if there has been oxidation formed in the joint the oxidation is an insulator not a conductor. The job of the pastes is to stop that oxidation process. The oxidation being more insulator than conductor causes a point of high resistance and a voltage drop. The current being forced past the problem spot will make heat and that will sometimes improve the conductance thus bringing the voltage up and improving how things run after the slow start.

The idea of testing the resistance of the wires out of the circuit would look for a wire that has something like your splice and how that effects the resistance when tested in different pairs as explained above. The other test you could do yourself is testing wire to wire with them disconnected and not attached at one end. If you measure resistance it should be zero meaning the wires are not shorted any place. The better test is to put power and a load across the wires. Something like a lightbulb could be used. Disconnect both ends and wrap one end in some tape for safety and then put say 120V with a load (lightbulb) in series. The bulb will limit the current if 100W to something like 1 amp but would subject the wires to 120V potential. If two wires had been somehow damaged and touching each other the voltage will jump the gap underground and cause the bulb to light or glow dim. They have test rigs with transformers to get closer to the insulation ratings of the wire but the simple lightbulb test would show a damaged wire most likely.
Your description doesn’t sound like that kind of a problem though if you had something like that underground the fault would have heated up and got worse and popped the breakers. What it sounds like to me is an oxidation problem in one of 8 places. The 6 wire connection points and 2 at each end of the splice. Start with the easy ones the wire points first. Take the wires out and shine them up good with scotch bright pad even dip them in something acidic like white vinegar and let them soak. Stronger acidic might work quicker but test it out on something first. After everything is clean recoat with grease for aluminum wire and test with your meter and by running your machines. If that doesn’t do the trick then look at the splice. Then and only then would I be thinking about replacing the wires.
 
Thanks for the detailed info. I can certainly try to clean up the wire ends. The splice is crimped so there's nothing I can do except replace it with another one.

So back to this copper vs aluminum question. With aluminum, they're going to use the required guage to give me the needed capacity at the other end. With copper, they'll use smaller wire to give me the same capacity, and charge me a bunch more. Copper doesn't last any longer. So as a consumer I don't see any real benefit to paying the higher price for copper.
 
Update...

I contacted the builder who sent out the electrician that did the original wiring on the house. He tested resistance as mentioned here, by disconnecting all the wires and testing the loop in pairs. It turns out there is an open circuit, a complete break, in the common wire. There was no continuity. The good news is that he is "pretty sure" that the wires are through conduit.

He then took away my 220v circuit and (temporarily) used one of the black wires in place of the common. That fixed the 110v circuit completely and just confirmed what we already knew. So now I'm waiting for an estimate to pull all the cables, replace the common (and inspect the others since they're out) and hook everything back up. He agreed to cut me a break on the cost since they did the original installation. He also said instead of pulling out the old cables they can just run a new common cable 18" deep, which would save me a few bucks. I don't know if I like that idea.
 
If it's in conduit you can use the neutral as a pull wire assuming the insulation will not break.
 
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