Use of Aluminum Conductors

[charlie b]

I am seeking opinions, and if available, a history lesson, on the early downsides of AL conductors.

The electrical group at a military base is opposing the use of AL in all circumstances, despite the fact that the Unified Federal Criteria (UFCs) specifically allows it in specific circumstances. Here is their most recent set of reasons for forbidding AL:

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I agree the initial cost of aluminum can be lower than copper but in the long run copper is always better.

(Here I omit their discussion of copper conductors.)

Aluminum Conductors:

1. Initial Cost: Aluminum conductors are generally less expensive than copper conductors, with prices ranging from $0.50 to $3 per pound, depending on the specific alloy and application.
2. Installation Cost: Aluminum conductors can be installed using standard tools and techniques, reducing labor costs.
3. Operating Cost: Aluminum conductors have a lower conductivity than copper, resulting in higher energy losses and increased operating costs over time.
4. Maintenance Cost: Aluminum conductors are more prone to corrosion and require more frequent maintenance than copper conductors.
5. End-of-Life Cost: Aluminum conductors can also be recycled, but the process is less established than for copper, making it less valuable at the end of its life cycle.

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Here are my opinions:

1. Item 1 is likely valid, thought its cost numbers might be out-of-date.
2. For Item 2, I don't see a relationship between standard tools and reduction of labor costs (as compared to using the same tools for copper).
3. I think item 3 is not valid, as it does not account for the fact that you must use larger AL conductors for the same ampacity.
4. Item 4 is what I am questioning. I believe it might have been true decades ago, but not with the aluminum alloys in use today.
5. I know nothing about recycle values. But I don't think they should come into the discussion for designs i9ntended to last 40+ YEARS.

Can anyone shed some light on this issue?

 

[infinity]

IMO if they're installed properly the more maintenance thing is a myth. I would just use all compression connectors and there would be no maintenance on the conductors themselves.

 

[don_resqcapt19]

As long as the alloy is the 8000 series, there should be no problems. Note that as far as I know, no aluminum conductors using the 8000 series alloy smaller than 8 AWG are on the market.

However the client is always correct about things like this. None of the industrial plants I worked at would permit aluminum conductors.

 

[suemarkp]

Even today, I think aluminum in contact with the earth still causes it to corrode and degrade. Code doesn't allow bare aluminum buried in the dirt or close to earth. Of course, most conductors will be insulated, but a crack or nick in the insulation that lets earthy water into it will start it to corrode away. You'd get a current leak whether the conductors were copper or aluminum, but the aluminum ones are going to turn to dust at some point if exposed to wet earth. So I could see some aversion to any buried aluminum conductors, especially on a military base where the earth could move. But above ground, and inside of buildings, I don't see an issue other than possible degradation from corrosive gases such as chlorine or byproducts of military equipment.

 

[charlie b]

I am specifically seeking their approval to use AL for service conductors (i.e., from the service transformer's secondary terminations to the main service panel's main breaker). They would be insulated, sized in the 250+ KCMIL range, and run underground in schedule 40 PVC.

 

[infinity]

I am specifically seeking their approval to use AL for service conductors (i.e., from the service transformer's secondary terminations to the main service panel's main breaker). They would be insulated, sized in the 250+ KCMIL range, and run underground in schedule 40 PVC.

I wouldn't hesitate to use XHHW aluminum for that.

 

[gene6]

When I have done work at the shore (near the ocean) I see aluminum start to oxidize after about a year, AL busbars and lugs in NEMA 3 panelboards.
I have also had issues with aluminum wire in livestock and pool facilities that have a slightly corrosive atmosphere. (We had a ton of service calls to a YMCA)
The problem with aluminum oxide is its not conductive like copper oxide, so the more it oxidizes the more it heats up then the more the connection degrades.
Copper tolerates a wide margin of installer error, and allows re-torquing lugs etc. Aluminum issues can happen if people make slight errors.
If its anything important like defense / healthcare / critical infrastructure I'd be inclined to stick to copper and look to save on costs in other areas.
Whatever you choose spell out clearly in your engineer job documents to grease it with a suitable anti oxidation grease, so then you don't have people debating if its required or not.
I think the grease solves most issues.

 

[Dennis Alwon]

When I have done work at the shore (near the ocean) I see aluminum start to oxidize after about a year, AL busbars and lugs in NEMA 3 panelboards.
I have also had issues with aluminum wire in livestock and pool facilities that have a slightly corrosive atmosphere. (We had a ton of service calls to a YMCA)
The problem with aluminum oxide is its not conductive like copper oxide, so the more it oxidizes the more it heats up then the more the connection degrades.
Copper tolerates a wide margin of installer error, and allows re-torquing lugs etc. Aluminum issues can happen if people make slight errors.
If its anything important like defense / healthcare / critical infrastructure I'd be inclined to stick to copper and look to save on costs in other areas.
Whatever you choose spell out clearly in your engineer job documents to grease it with a suitable anti oxidation grease, so then you don't have people debating if its required or not.
I think the grease solves most issues.

I don't believe this is true with the new aluminum alloy mentioned earlier. Or are you talking about the newer aluminum

 

[jim dungar]

A copper versus aluminum wiring argument is not usually based on science or facts so it is basically due to irrational fears. Good luck.

For at least 50years, off the shelf transformers have typically been wound using aluminum conductors. I remember an engineer that claimed the windings would melt before their protective fuses would clear during a short circuit.

 

[gene6]

A copper versus aluminum wiring argument is not usually based on science or facts so it is basically due to irrational fears.

Well when I took a look at the science and facts, it seemed pretty clear,
Just AL terminations before and after 2k hours in salt fog, which is common at the shore;

https://copper.org/applications/electrical/building/pdf/A6108.pdf

 

[charlie b]

When I have done work at the shore (near the ocean) I see aluminum start to oxidize after about a year, AL busbars and lugs in NEMA 3 panelboards.

Thank you for sharing this info. It will not apply to the project for which I posted this thread. This military base is nowhere near a salt water body.

 

[charlie b]

Well when I took a look at the science and facts, it seemed pretty clear,
Just AL terminations before and after 2k hours in salt fog, which is common at the shore.

I will make sure the design team includes an installation requirement that salt fog is not to be used as a cleansing agent.

 

[jim dungar]

Well when I took a look at the science and facts, it seemed pretty clear,
Just AL terminations before and after 2k hours in salt fog, which is common at the shore;

Which meaning of my qualifier word usually is giving you grief?
I see nothing in the OP list that referred to environmental misapplications.

I firmly believe that utilities use aluminum conductors, including substation bussing, and appropriate connectors in outdoor areas which occasionally experience salt fog.