Cost of Copper

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hardworkingstiff

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Wilmington, NC
I was speaking to an EE today and I asked him what his thoughts were on using Al. conductors for service feeders (paralleling specifically). He said it was fine so long as someone checked it with torque wrench once a year.

That would entail having the PoCo cut the power once per year for inspection. If that is what needs to be done to keep integrity, the cost of copper may not be so high after all.

Thoughts?
 
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I've never used AL on my designs. Never have. Never will.

Prices are higher for copper. But the time, money and effort put towards the maintenance of AL conductors, far surpasses that for copper conductors, IMO.
 
With the series 8000 AL I don't think you have to tighten the lugs every year. They tell me it has almost the same properties as copper. I used to be a die hard copper fan until it became 3 times higher than AL. I have since swallowed my pride and went for the almighty profit.
 
rr said:
I've never used AL on my designs. Never have. Never will.

Prices are higher for copper. But the time, money and effort put towards the maintenance of AL conductors, far surpasses that for copper conductors, IMO.
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I agree. I design based on copper. If the owner wants to VE to aluminum, then he/she will need to direct me to do it in writting. That way, problems or maintenance issues that come up are at the written directive of the owner.

Also, does anybody know the actual savings from going from copper to aluminum. Say you have a 400 amp feeder 100' long with 4#500mcm and #3 gnd in 3.5" rigid. What would be the savings after you upsize the conductors and the conduit? Oh yeah, subtract off 10 compression lugs for the alum while your at it.
 
What would be the savings after you upsize the conductors and the conduit?
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In most cases, if you use compact strand conductors, you will not have to upsize the conduit. That is the reason the aluminum industry started making compact strand conductors. In this case you could use 700kcmil compact strand aluminum with an ampacity of 375 amps. The 500 kcmil copper will cost 2 to 3 times as much as the 700 kcmil aluminum.
Don
 
I never spec Aluminum because it not being as pliable for the installer/EC, however if they don't mind upsizing the wire, working more gingerly, and paying whatever extra upfront cost. Then, I don't mind...because I know how expensive copper can be. However, I don't want them mixing it. Plus, I will not allow it outside, because of corrosion. Fine for me, as long as the AHJ doesn't mind!

That's my take...

Lady :)
 
Regarding savings it works out to be 30% to 40% savings on the cost of the feeder, conduit & installation to use a AA-8000 product rather than copper.

Oh and yes you can use mechanical lugs in lieu of compression for AA-8000.

Oh and yes you can use it outdoors in wet locations (most utilities already do and have for a long time)

Oh regarding checking it with a torque wrench is not necessary a simple thermal scan can show any issues. But I know for a fact that some of the Stabiloy conductors I have installed in the past have never been checked and the facilities are still operating. Probably not a great maintenance plan you should check both copper or Aluminum with a standard maintenance plan.

The perception that AA-8000 is somehow a bad product is simply ludicrous and trying to convince certain stubborn misinformed engineers is not a whole lot of fun.

I hope none of you take any offense but please before you make blanket statements research the product and some of the many installations (Like your home electrical service)

-Ed
 
I recently heard that Aluminum Feeders were used at the Epcot Center in Disney. As mentioned Aluminum needs to be torque periodically because Aluminum shrinks. I don't think it would be efficient in a residential application.


Justin J. Walecka
 
JJWalecka said:
As mentioned Aluminum needs to be torque periodically because Aluminum shrinks. I don't think it would be efficient in a residential application.


Justin J. Walecka
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A lot of conflicting views I will add more. :)

If you continually 're-torque' you will crush the conductors and likely break something eventually.

IMO the best bet if your worried would be an IR scan but the same should be done for copper as well.

Aluminum is used often in residential for range receptacles, feeders and services. :)
 
If there is a worry about mechanical lugs with AL conductors loosening than why not use compression lugs. Certainly the savings generated by using AL over CU will more than pay for the higher cost of installing compression lugs. Sounds like a win-win situation, cheaper conductors and a higher quality installation over a mechanical connection.
 
As mentioned Aluminum needs to be torque periodically because Aluminum shrinks.
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Mechanical wire connectors for any type of wire should never be re-torqued. If there is any type of problem, the wire should be cut back and installed in a new terminal and torqued per the manufactures instructions.
Don
 
I usually use Aluminum for my SE conductors, and I've never had a problem. Some installations are 30 years old. I go back the next day or so after I torque them to re-check. Aluminun is soft and I have noticed that it will creep and need re-tightening a couple of times. After that, the connection is OK. Just my opinion.
steve
 
hillbilly said:
I usually use Aluminum for my SE conductors, and I've never had a problem. Some installations are 30 years old. I go back the next day or so after I torque them to re-check. Aluminun is soft and I have noticed that it will creep and need re-tightening a couple of times. After that, the connection is OK. Just my opinion.
steve
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Do you use a torque wrench?
 
i have used a torque wrench on copper terminations, (500 kcmil) and found that after several cylces on and off of the 500 HP motors that those terminations fed, the lugs needed to be tightened again. just a couple foot pounds is all
 
i have used a torque wrench on copper terminations, (500 kcmil) and found that after several cylces on and off of the 500 HP motors that those terminations fed, the lugs needed to be tightened again. just a couple foot pounds is all
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NO, they don't. This "relaxation has been taken into account when the manufacturers wrote the torque specs.
The following is from this document.
As part of annual maintenance, a facility performs routine torquing of all electrical connections. Is this a good idea? Unfortunately, the answer is no! Evidence shows that this practice can do as much harm as good. Factory Mutual states that "once properly made, an electrical connection should never need retightening". ... Systematic torquing could create a problem where there was none due to overtightening. An overtorqued connection can be just as dangerous as a loose connection. ... Is it O.K. to check the torque on a connection? Absolutely, but any further action should not be taken until the condition of the connection is evaluated.
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hardworkingstiff said:
Do you use a torque wrench?
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No, actually I divide the recommended torque by two and find a rock that weighs that much (plenty of rocks around here). Then I tie the rock onto a 24" power handle (actually a whittled hickory stick) and use that to torque the screw. I have to be careful not to let the rock drop as the inertia will add too much torque. On re-tightening, I lift the rock about 6" and let it drop. I figure that the breakaway torque on the screw will offset the added torque from the falling rock and the result will come out just about right.
steve
 
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