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When Will Copper Get Too Expensive?

Posted July 17, 2011 12:00 PM

In this issue, there are two items that directly or indirectly deal with the price of copper. In one, two trade associations warn that cables made with copper-clad aluminum wire don't meet safety regulations. In the second, cable maker Nexans says that despite the high price of copper, it doesn't see a significant move towards cheaper materials, such as aluminum. There must be a breaking point, though, isn't there? At what price will alternatives to copper wire be seriously pursued?

The preceding article is a "sneak peek" from Wire & Cable Technology, a newsletter from GlobalSpec. To stay up-to-date and informed on industry trends, products, and technologies, subscribe to Wire & Cable Technology today.

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Power-User

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#1

Re: When Will Copper Get Too Expensive?

07/18/2011 8:43 AM

Alternatives to copper wire will be seriously pursued when the price of copper goes over the price of the alternative.

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Guru

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#2

Re: When Will Copper Get Too Expensive?

07/18/2011 8:48 AM

Funny they the power companies already run aluminum wires from the pole to the house meters.

It has also pretty much common knowledge that most of the current flow occurs at the surface of round wire so I don't see a problem with copper clad aluminum wiring being able to carry a load safely under most residential conditions.

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#4
In reply to #2

Re: When Will Copper Get Too Expensive?

07/18/2011 10:20 AM

Skin effect depth at 50 or 60 Hz is about 8 mm, so copper cladding aluminum wire only serves to help prevent corrosion issues in home wiring. It does very little to increase the current carrying capability. 12 AWG copper clad is only rated for 15 amps not 20 like solid copper. I have copper clad wiring in my circa 1973 home and I replace it any chance I get. I want that crap out of my house. The voltage drops under load are noticeable and annoying. (lights dim, etc.)

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#15
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Re: When Will Copper Get Too Expensive?

09/23/2011 4:40 AM

In large cables especially compressed segment paper lead where the connections are made by hydraulically crimped lugs aluminium is probably almost adequate.

In small stuff my experience from early in my career (73) is similar to your comments. The corrosion, creepage, breakage were all problems we didn't need. Luckily in this country it dissapeared as quickly as it arrived.

Maybe a Cupro Aluminium alloy may work especially if it is plated. Cupro Aluminium is a pretty special group of alloys in terms of strength toughness and corrosion resistance but I can't comment on its conductivity.

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#3

Re: When Will Copper Get Too Expensive?

07/18/2011 9:01 AM

The problem with aluminum, clad or not, is that after some time, the compressed aluminum, due to movement and vibrations, loosens at its connection point, creating a higher resistance to current flow and hence, heat and the possibility of fire. Once the connector/connection issue is cost effectively solved, aluminum wire will be a safe replacement for wiring buildings.

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#6
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Re: When Will Copper Get Too Expensive?

07/18/2011 11:11 AM

Finally, someone answers this question like an engineer rather than an accountant - GA!

Using aluminum wire for service entrance conductors in residential applications is generally a bad idea because the connections loosen over time, and a loose connection in a home electrical panel is unlikely to be discovered until after a it arcs badly enough to do serious damage and/or burn the house down. To be blunt, I wouldn't want the stuff in my house.

Some proponents of aluminum wire argue that installing a compression crimped connector on the end of the aluminum wire fixes the problem of connections loosening over time, but the crimp connectors for large diameter wires and the tools to install them are expensive, so few residential electricians bother to use them unless it is required by local inspectors.

The only places that I feel comfortable using aluminum conductors is in large scale applications like manufacturing or power distribution which have Preventive Maintenance programs that include periodically tightening electrical lugs and terminals.

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#9
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Re: When Will Copper Get Too Expensive?

07/19/2011 12:12 PM

I have aluminum service conductors coming into my 38 year old house. Properly torqued, they don't loosen over time. I checked mine a few years ago and they were tight, very tight. Most panels are designed to handle the aluminum service conductors and the lugs do a fine job with the aluminum. However, from the panel to the loads, copper is my choice.

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#10
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Re: When Will Copper Get Too Expensive?

07/19/2011 1:24 PM

You should consider yourself fortunate. I have worked on several service calls that involved replacing residential electrical panels in which the aluminium conductors loosened over time resulting in intense arcs which caused the wire, the lug, and panel's bus bars to heat up, melt, and short out. Anytime I see aluminum conductors in a panel I habitually tighten the lugs - about 50% of the time at least one of the lugs turn freely for at least one full turn.

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#11
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Re: When Will Copper Get Too Expensive?

07/20/2011 11:32 AM

I suspect some installers just tighten the clamps down good and snug. Whatever that is. In their minds, tight enough is good enough. I haven't checked, but I'd wager that the panel manufacturers specify a torque for the lugs which is important for proper clamping of aluminum and copper conductors. Do electricians carry around torque wrenches?

I work in the aerospace industry and proper crimping of lugs can be crucial in high current applications. We had a lessons learned session where a very high current power supply interconnection wire was overheating (letting out the magic smoke) even though the wire gauge and the lug was properly sized for the current levels.

Using an electron scanning microscope to view a sectioned crimp zone revealed the root cause. The issue turned out that the crimp was not deforming the conductors in the clamping zone (filling in the interstices between the strands) that resulted in a higher resistance termination and when you are passing hundreds of amps, a little resistance goes a long way. An ideal crimp actually creates a gas-tight seal. Round strands get deformed into hexagonal-like shapes filling in all the gaps between the strands. Of course you can go too far and over-crimp where you create a cold-working failure of the metal.

Most people hardly give crimp lugs a second thought, using a $3 dollar tool to crimp those little lugs for automotive and boat wiring. However, poorly done crimps can cause disaster. Using the proper size lug for the conductor and using a quality tool is important.

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#12
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Re: When Will Copper Get Too Expensive?

07/20/2011 1:42 PM

Do electricians carry around torque wrenches?

Some do, some don't. The only protection that the homeowner has is the good word of the contractor who's primary goal is to make as much profit from each job as possible. In many cases, profit-centered contractors only take extra steps to perform a task if an inspection is likely to detect that a step was skipped - i.e. unless the inspector carries around a torque wrench as well.

A point well worth considering when deciding whether to spend an extra 20% on 40 feet of wire is that electrical services with copper conductors are far less likely to experience any sort of mechanical failure because basically all the electrician has to do with copper is tighten the lugs until they are tight, and when they are checked 5 years or 20 years later they are usually still tight. With aluminum on the other hand...things happen.

You should probably consider checking your lugs at some point if you service is 38 years old. Unless you have your own set of hot work gear you'll have to call your local utility company to schedule a truck to come by (depending on your locality there may be a charge for this) and disconnect power to your house because you need to check lugs on both the line and load side of your main panel and your meter base. In most cases, the utility truck will not wait around for you to perform your task, so after you've checked your lugs, you should be prepared to wait for another truck to come by and turn the power to your house back on.

Good luck Brave Sir Robin!

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#13
In reply to #12

Re: When Will Copper Get Too Expensive?

07/20/2011 10:31 PM

I already checked mine. They're good. No need to kill the power, I have class II gloves with covers. Using those with FR long sleeves and a face shield provides plenty of protection from arc flash. Tools get covered with polyolefin heat shrink except for the business end.

Cheers !

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#17
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Re: When Will Copper Get Too Expensive?

09/23/2011 5:19 AM

Wish I could give you more than one GA for that one.

An interesting thing I've noticed over the years has made me reassess my opinions somewhat. I was always a proponent of Hex dies until I eventually realised that the ends that failed on Dragline loop cables were the Hex crimps and the GE factory Indent Palm type lugs just kept on keeping on. When cut through the visual image (sorry no scanning electron microscope in my tool box) of the indent lugs is a fully compressed point and many hex jobbies are rather open. These cables were copper.

My pet hate is the cheapo mechanical hex crimper with indexable plate dies that one is meant to use about 4 times to create a crimp joint (they make about a 3mm wide half baked crimp). They are so flimsy the lug barely crushes, especially at maximum size say 120 sqmm.

I call them battery cable crimpers.

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#16
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Re: When Will Copper Get Too Expensive?

09/23/2011 5:01 AM

Agreed

Thermography is also a good idea and maybe a sampling system like Vesda to detect the first signs of heating too.

I also feel the only lugs to use are bimetal in most cases, then at least there is a copper lug to to bolt or clamp.

I once had to test and repair (by replacement with copper) about 50 sets of (HV linesman's) portable earths made of 50 sqmm flexible Ally. The copper replacements were 35 sqmm and much lower in resistance when measured at 250 amps injected. On cutting samples of the cable at random lengths along the cable I found reterminating the ends was not really viable due to formation of oxides on each strand along the entire length. We all know Aluminuim oxide is probably the best insulator around, so it aint too nice inside the joint.

The jointing compound inside the lug will only cut the invisible oxides on new cable, not the grey stuff found when reterminating.

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#5

Re: When Will Copper Get Too Expensive?

07/18/2011 11:08 AM

Same question, different metal: When Will Silver Get Too Expensive?

Answer...it did and it has been. That's why we use copper conductors instead of Silver, though Silver has superior properties. The use of Silver has been reduced to critical components of the electrical system, such as contacts and silver-solder that melts at a suitable temperature to replace lead in pick-and-place robotic assemblies for your cell-phones and LED monitors. But when a really-critical piece of equipment, like a space shuttle or a satellite or a nuclear reactor needs only 'the best' in some corner of the installation, silver is used for transformer windings, electromagnets, and wiring even now...when cost is irrelevant.

So...back to AL versus CU.

Aluminum wiring is NEC approved. Now that AA-8000 series alloys and a few specialty alloys for particular applications have been developed, replacing the previous 1305 series, new aluminum conductors have better conductivity, creep resistance, strength, and workability than previously available. They are nearly as easy to pull through conduit as their copper counterparts. The key point is that advances in alloy properties appear to have removed much of the dissimilar expansion problems that resulted in past failures at connections. Also, the heat and electrical conductivity (performance) of copper-clad aluminum is closer to solid/stranded copper than the 80% or so capacity of just aluminum, and still has the weight and cost advantages. It does require larger sizes, even with the standard "compact stranded" format, so the savings are not as large as just the AL-CU cost since some conduit runs must be larger.

Note that a market-full of connecting products is now available that are "rated" for terminating aluminum conductors, and this rating is still critical to ensure a safe installation, so the small premium is worth it while the cost comes down. It is fully suitable for, say 1/0 sizes and above, where the connections are stripped with a correct tool to avoid damage, immediately treated with an anti-oxidant, terminated with correct torque on a rated lug or a 2-hole compression fitting. I could even see panel feeders using aluminum, if the spacing is made available by correct selection of a larger panelboard 'tub'.

The added labor manhours is negligible with proper training in the above, though most shops will tack-on a bit of a premium cost for the added care and treatment. This will be minimized if and when aluminum or CU-clad-AL becomes more standard.

Small aluminum conductors terminated on vibrating equipment with unrated steel screws WILL still fail, so the equipment must always match the materials and application, and equipment worldwide uses pigtails and steel terminals that are appropriate only for copper. That factor is the main one preventing use of aluminum (or clad) from use in branch or equipment circuits, though the oxidation issue is also important. AL cannot be used directly to a motor, due to the current UL listing limitations on doing this.

Note that a copper 'default' a couple years back, by a Chinese investment bank of some kind playing with naked futures contracts for copper that did not exist, caused the price of copper to nearly double in short order. Go back and look at past "sudden spikes" and you'll find them right after a futures expiration when delivery was demanded on the contract...but no copper was actually available to fulfill the contract...resulting in a "delivery delay" (the nicer term for letting someone off the hook on a commodity default). This could easily happen in Silver (which is at a massive 4.5 times over-sold on paper) but is not likely in aluminum, so AL prices should remain fairly stable at the inflation rate with much less volatility than the others.

Bottom line, on suitable service and larger trunk cabling load applications, AL saves at least 25% initial material cost now, compared to the equivalent CU at similar capacity. This savings will only increase with an increasing demand for copper during a recovery and future growth of the construction industry (which will drive up the price).

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Commentator

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#8
In reply to #5

Re: When Will Copper Get Too Expensive?

07/19/2011 12:47 AM

Aluminum power cables are mandatory in India since 1960s. The termination is done using crimped tinned copper lugs and a antigalvanic action grease is applied at the interface between the two metals. The house wiring is still done using copper wires. I have done wiring using crimped sleeves using antigalvaic paste at interface and a tail of copper at the end of each run successfully.

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#7

Re: When Will Copper Get Too Expensive?

07/18/2011 12:24 PM

Copper will get to expensive when the cost of replacing stolen copper wires gets higher than using a more affordable and effective alternative.

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#14

Re: When Will Copper Get Too Expensive?

07/26/2011 8:03 AM

When enough gets stolen causing the price to continue to rise, hoarding will begin and the government will start a strategic copper reserve, which will guarantee shortages and high prices forever. Perhaps then it will be profitable to develop a composite substitute for copper if that is indeed possible.

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