Aluminum Conductors

[charlie b]

I would like to ask for information, experiences, recommendations, and whatever I can get on the issue of the use of aluminum (AL) conductors. The NEC has allowed AL conductors for a very long time. The Department of Defense (my present employer) publishes its own “building codes” in the form of “Unified Facility Criteria (UFCs).” The relevant UFC allows AL conductors above a certain AWG size. I am dealing with a military base that has adopted an even more stringent requirement: “copper only.” I would like to get them to reconsider that requirement. But it would help if I could present some supporting technical substantiation.

Questions:

• Am I right in believing that AL conductors had a bad reputation in decades past, and that the technical issues included poor electrical connections, special requirements for making those connections, corrosion, and overheating to the point of creating a fire hazard?
• Am I right in believing that those issues have long since been resolved, and there is no longer any reason to be concerned over the safety of using AL?
• If use of AL conductors is safer now than in decades past, what has changed? Is it something to do with manufacturing (i.e., materials science)? Is it related to installation techniques?
• If AL is used for, say, service or feeder conductors, will that require periodic maintenance to ensure that the connections remain tight?
• Do you use AL conductors when you are given the option?
• Are you aware of any recent failures (e.g., fires) for which the cause was traced to AL conductors?
• What else should I know about AL conductors?

 

[petersonra]

The only issues I am aware of with AL conductors was when they were used in homes with receptacles that had terminals that were not suitable for use with the small gauge AL conductors that were used to save money.

I don't recall it was ever an issue beyond that, but like a lot of things it snowballed into the idea somehow that AL conductors are just sitting there waiting to kill someone.

 

[zbang]

My understanding is that aluminum got the bad rep from residential branch circuit wiring. Also that improved alloying of the wire and redesigned device terminals addressed the excessive creep that lead to loose connections (which lead to fires). I'm also going to guess that compact strand designs for larger sizes would have helped with creep and loose connections.

Periodic maintenance- above regular testing & maintenance that all equipment should get (and is usually ignored)?

Note that I don't have citations to support this without some searching.

 

[Besoeker3]

We have Al conductors for Anodising plants. Some are 40 kA. We have not experienced problems with those.

 

[Todd0x1]

Is the base located near the coast? Perhaps the requirement is based on potential for corrosion. Do their specs also require copper bus only in panelboards and switchgear?

 

[gar]

230119-1557 EST

I think you need to understand some basic differences between copper and aluminum.

Copper is quit ductile compared to aluminum, and does not work harden as quickly as aluminum. Copper oxide is a good conductor compare to aluminum oxide, where as aluminum oxide is a very good insulator, and used for this purpose. Aluminum electrolytic capacitors are an example.

I would never put aluminum wiring in my home, or from the pole transformer to my home. None of the breaker box or anything else would be anything except copper.

.

 

[don_resqcapt19]

The original 15 and 20 amp aluminum had much more thermal expansion than the currently used alloy. That excessive thermal expansion combined with the typical steel screw used on low end residential wiring devices, often resulted in excessive heat at the terminations, and sometimes that resulted in structural fires.
The new alloy aluminum was available as a single conductor for a couple of years in the mid 70s. I don't think the new alloy was ever used in NM cables.
I worked on an apartment complex with about 125 units in 75-76. We used the new alloy single conductors along with CO/ALR wiring devices. For a number of years after that, I ran a service truck for that contractor. There were no more issues with aluminum project than there were with similar projects that we had done using copper.

That being said, most of the projects I worked on after that all used copper conductors. Typically because that is what the specifications required.

As far as I know, there are no aluminum conductors smaller than 8AWG on the market at this time. You can get 12 and 10 AWG in Copper-Clad- Aluminum in both single conductor and NM cable at this time. The only real issue with the use of CCA is wire connections. While wiring devices that are marked for use with copper conductors can be used with both copper and CCA, only wire connectors marked AL or CU/AL can be used with Copper Clad Aluminum at this time per the listings.

 

[don_resqcapt19]

230119-1557 EST

I think you need to understand some basic differences between copper and aluminum.

Copper is quit ductile compared to aluminum, and does not work harden as quickly as aluminum. Copper oxide is a good conductor compare to aluminum oxide, where as aluminum oxide is a very good insulator, and used for this purpose. Aluminum electrolytic capacitors are an example.

I would never put aluminum wiring in my home, or from the pole transformer to my home. None of the breaker box or anything else would be anything except copper.

.

But aluminum oxide is very brittle and the normal termination will shatter the aluminum oxide. The typical screw termination is gas tight when made up correctly, so the oxide does not reform.

 

[Buck Parrish]

Perhaps you can use a small portion of the following statements from a laymans point of view.

I just installed some 4/0 AL SER yesterday and had to convience the customer that it was fine. Because you"re right, their was and still is a stigma attached. But it's been my experience that those that are worried about it are not Electricians.

Most of the bad reputation comes from branch circuit wiring. I have seen numerous outlets burn , melt but not burn the house down, ussually from changing the outlets from AL rated to copper only rated. .
Personally I would not use aluminum in my home except for mains and sub panels. But sub panels that are underground, I use copper. It seems water has a bad effect on AL . If that cable gets knicked and the conduit fills up with water. You will have the potential for a problem.

I wired a school the city wanted to cut cost . Well one of the things that they cut was the copper wire. Instead they had us use Aluminum wire and MAC adapters at our terminations. It's a better conductive metal compression fitting that goes over the ends of AL to make a better termination it has antioxant in it under the compression point. . That was the only job I used them on.

On another job yesterday whilst I had a panel cover off and the power was cut off. I tried to tighten some lugs that had 4/0 AL installed 20 years ago . It was still tight. I could not budge it. It's been there all that time without getting loose.

I've been told it is safer now. That the terminals are made better, more conductive, maybe even the AL has alloys that help prevent it from breaking down.
What gets me is that home owners maybe even miltary bases insist on using all copper. But then the power company feeds it with Aluminum. Think of it, all the mains are Aluminum.
Perhaps what might help your endeavour most . The Next time you gaze out over a big city like Chicago or Seattle at night. You can see lights way out as far as you can see all the way until over the horizon thats all you see.
At every bussiness every residence. Their main feed is Aluminum.

 

[charlie b]

Many thanks for all the responses. It will greatly help in my discussions with the base.

 

[Besoeker3]

Many thanks for all the responses. It will greatly help in my discussions with the base.

Slight diversion........you are a a gentleman of the finest order. I appreciate your posts here.

 

[jim dungar]

The vast majority of "off the shelf" dry type transformers have been built using aluminum windings for almost 50 years.

My experience has been, when dollars count aluminum conductors are almost always value engineered in for feeders over 100A.

 

[mayanees]

I spent half my career with the big industrials, DuPont, SPCO, P&G, General Foods. and they all used copper wiring for everything. But a big internet provider that I deal with as a consultant, who hopes to, or claims to have data centers every 60 miles across the USA, uses aluminum for transformer secondaries at 480V, 3200 amps, with the stipulation that the termination points be accessible and inspected on a typical maintenance schedule.
I think this is a smart way to save money, even though aluminum isn't as cheap relative to copper as it used to be. The lengths are typically somewhere around 150 feet and the savings are significant.

 

[Knuckle Dragger]

I have inspected and re terminated splices and devices in apartment complexes converted to condominiums.
I didn't find that many failed terminations. (No more than copper) These units all had electric baseboard heat as well.
For the most part the success rate of the termination depends on technician.
Note: For the most part I use Al #2 and up

 

[hillbilly1]

Most of the failed installations have been improper connections. Around here well drillers were bad to shove a #10 cu in the same lug as a 4/0 AL on mobile home disconnects. It would last a few years, then eventually corrode causing a bad connection.

 

[augie47]

As to termination there are several references to re-torquing the connections and the advice seems to be:
proper procedure is torque to spec and leave it alone. If its torqued to spec, it should never come loose. Retorquing can damage the conductors and cause a worse condition. only proper method is to cut used strands of wire off, strip insulation off, and terminate again to spec

 

[gar]

230119-2021 EST

If you have studied or played with various materials you will have learned that there is usually an elastic region, and beyond that range you yield the material.

If you stress material in the elastic region, and relax that stress, then with zero stress the material will return to its original state. Exceed that yield point, then relax the stress to zero, and the material does not return to its original state. And it does a little work hardening.

Copper does not work harden as quickly as aluminum. And as I mentioned copper oxide is not a high resistance material, whereas aluminum oxide is a very good insulator.

If you stay below the yield point of iron based alloys, then you are close to a no fatigue level. Whereas non-ferrous materials do have a fatigue life when stress is held within the yield point.

.

 

[gene6]

There are vastly different considerations for civilian and military infrastructure. When working for DoS on Embassies and Consulates we never used anything aluminum. But they were ultra concerned about everything with 1:1 isolation on every service entrance.

 

[steve66]

230119-1557 EST

I think you need to understand some basic differences between copper and aluminum.

Copper is quit ductile compared to aluminum, and does not work harden as quickly as aluminum. Copper oxide is a good conductor compare to aluminum oxide, where as aluminum oxide is a very good insulator, and used for this purpose. Aluminum electrolytic capacitors are an example.

I would never put aluminum wiring in my home, or from the pole transformer to my home. None of the breaker box or anything else would be anything except copper.

.

Millions of installations have aluminum either for larger wiring (not branch circuits so much), transformer windings, or panelboards, etc. The list goes on and on.

And our local power company always used al for the service conductors (back when they provided the service conductors), and there are thousands of these installations still in uses from probably the 1950's through the early 2000's. And that's just one POCO....

 

[acrwc10]

Almost every electrician in the field that says aluminum is no good, when asked why, they cannot say what the problem is. I have installed aluminum service conductors, feeders and large branch circuits for over 30 years. I have never had any problems with it. I have also never seen aluminum fail where copper would no have also failed. One of the problems I see with aluminum is when stripping the insulation if the conductor gets nicked it is far more likely to break the strand off.