Aluminum Conductors

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ggunn said:
I have designed a couple of PV systems for military facilities. The "no aluminum conductors" clause was in every contract.
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Probably more of a boilerplate specifications situation than actually considering if they are feasible for the application though.
 
kwired said:
Probably more of a boilerplate specifications situation than actually considering if they are feasible for the application though.
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Maybe so, but when it's in the contract it's what we deliver.
 
VirutalElectrician said:
So you're saying if they strung copper up 200' in the air, subjected it to high winds, rain, snow, ice, temperature extremes, etc, copper would not require any maintenance?
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Like the number of licks necessary to reach the center of a Tootsie-Roll Pop, we will probably never know.

Unless maybe somebody stumbles onto a seawater desalinization process that spits out copper as a waste product,
the way the oxygen extractors spit out waste gold in 20,000 Leagues Under the Sea.
 
VirutalElectrician said:
I keep seeing EMT mentioned. Is any sort of flexible metal conduit allowed? Or must it be actual EMT?
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Here is the Chicago amendment for 348.10. This amendment is based on the language that is found in the 2017 NEC.
1. Revise section 348.10 to read:
“Uses Permitted. FMC shall be permitted to be used:
(1) For the connection of motors or recessed luminaires
(2) In lengths not exceeding 7.62 m (25 ft) between junction boxes for branch circuits in concealed work fished into existing walls, partitions, floors, or hard surface ceilings where other work does not require or include removal of the existing finished surface
(3) For required flexibility at the termination of conduit runs.”
2. Insert new subsections 348.12(8) and (9) to read:
“(8) In lengths exceeding 1.83 m (6 ft) except where fished in existing construction
(9) Where exposed below the first floor except 1.83 m (6 ft) of any run shall be permitted to extend below the basement ceiling to connect to a cabinet, outlet box or junction box.”
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The use of flexible wiring methods is very limited in the 2018 Chicago Electrical Code.
 
retirede said:
I believe a limited length of MC is allowed to be fished in after the fact, but not allowed in new construction.
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Here is the Chicago amendment to 330. The amendment is applied to the language found in the 2017 NEC.
1. Revise section 330.10 to read:
“Uses Permitted.
(A) Existing Installations. Except where otherwise specified in this Code and where not subject to physical damage, listed Type MC cable with listed fittings and not exceeding 7.62 m (25 ft) in length between junction boxes shall be permitted for branch circuits in concealed work fished into existing walls, partitions, floors, or hard surface ceilings where other work does not require or include removal of the existing finished surface.
(B) Exposed Work. For exposed work only under the following conditions:
(1) In lengths not more than 1.83 m (6 ft), at terminations where flexibility is necessary;
(2) In lengths not greater than 1.83 m (6 ft) in accessible, but not habitable, attics and roof spaces where installed in accordance with 320.23;
(3) In lengths not greater than 1.83 m (6 ft), below the basement ceiling joists where it is necessary to connect a cabinet or junction box.”
2. Revise section 330.12 to read:
“Uses Not Permitted. Type MC cable shall not be used for any installation not permitted in 330.10.”
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charlie b said:
. 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.”
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Tell them that the US taxpayer would like a reconsideration of that policy.
 
electrofelon said:
Tell them that the US taxpayer would like a reconsideration of that policy.
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to keep out of trouble with political topic lets just say copper used in DOD projects is probably just a drop in a bucket compared to some other government spending that goes on.
 
kwired said:
Seen many times they ran EMT all over the place then pulled NM cable through it. Even if they did a decent job with the raceway install - why make it harder on yourself by pulling NM cable through it?
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Sure sign of a DIY/handyman job. Just do a casual check of YouTube.
 
230127-0542 EST

At low and high voltages copper oxide is a moderately good conductor.

At normal utilization voltages, say below 300 to 1000 V, aluminum oxide is a very good insulator. This a very thin oxide layer that prevents aluminum from continuing to oxidize. Aluminum when exposed to air oxidizes. This is a very thin layer so with a moderate amount of voltage it is able to be this very good insulator. Above some voltage the insulation breaks down, and conduction then occurs.

Certain materials or a good compression of aluminum wire to some other material can provide a a low resistance joint.

.
 
charlie b said:
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?
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Charlie, I am answering your questions first before reading all the other replies, as they are numerous, but I feel I can offer reasonable and logical answers since I have done lots of research on this subject over the years. Early in my career, I worked for an EC who did alot of service work on mobile homes (and I mean the old “mobile homes”-you know, the ones that caught fire and burned down Before the FD even showed up) where we would replace receps and fixtures on old AL romex. The Codes decision to ban the use of AL under #10 is most definitely the right call-even with new manufacturing in place since the 80s. AL that small is too easy to have issues.

That being said, in the early 80s when AL was getting a bad wrap for anything (feeders, branch circuits, services, you name it), obviously ALCO and all the other foundries didn’t want to lose that business. They went to their engineers and chemists and came up with the AA8000-an ALLOY, not straight AL. With this alloy, the wire became stronger than AL, lighter than the original, more durable when it came to expansion and contraction, and much better workability. If there was truly any more danger in using it, certainly the Code would not have allowed its use in any way shape or form. Yet, they did, as long as it was the alloy-not straight AL. And since the 80s theres been even more modifications and improvements that personally, I prefer it to copper for all our feeders and larger branch circuits.

Look at it this way: almost all utility feeders, whether through the air in tri/quad plex or underground in conduit or DB and even their transmission wires, are almost exclusively AL alloy or a mix with steel. Theres literally hundreds of thousands of miles of AL wire installed that fares totally fine in many extreme environments. MOST faults that do happen with AL could happen the same way for copper.

NECA/IBEW has their written installation standard about the proper use and installation of AL wire and there is no major disqualifications in using AL wire.

Most terminals, lugs, breakers, etc, carry a dual rating these days, leaving the possibility of installing AL to the wrong lug a thing of the past.

As with all trades and specifically electrical, proper installation following manufacture’s/Code requirements and industry best practice is the best way to ensure a safe and compliant installation. You can install a copper wire wrong and burn a house down just as much an AL feeder if you install it wrong or don’t follow code. One of the biggest installation hazards is guys “ringing” the conductor insulation-this is a major no-no! Not just for general wire installation, but especially for AL. It should always be “skinned” with a sharp knife or the use of a proper stripping tool for AL only.

We install alot of large gens for emergency backup. We pull AL feeders and cables all the time, unless copper is specifically called out. Only time theres an issue is when one of my guys is dumb enough not to use a torque wrench. Its cheaper, lighter and in larger sizes, much easier to work with compared to copper.

Along with that: just like ANY other electrical installation, periodic inspection and/or testing is important and required. Obviously NFPA 70B talks about alot of equipment industry standard and best practices for this. Even on resi meter combos, the mfr has their inspection and cleaning reqs. But honestly, how many homeowners do that or wanna pay us to come do it for them? Id say less than 5% in the whole continent. Even with that, Ive never heard of a fire due to AL wire failing in the last 20 years that wasn’t from an installation failure or a mfr defect. And each of those could happen to copper as well.

All in all, I know this post is long, but to put it short: outside of a few rare cases, mainly industrial applications, would I have a hard time sleeping at night after I installed AL wires to a panel or piece of equipment. If I do my research thoroughly on a product and get trained and have experience in its use and installation, there should be no problems at all with AL wire used in todays electrical systems.
 
SparkyBirdman said:
Charlie, I am answering your questions first before reading all the other replies, as they are numerous, but I feel I can offer reasonable and logical answers since I have done lots of research on this subject over the years. Early in my career, I worked for an EC who did alot of service work on mobile homes (and I mean the old “mobile homes”-you know, the ones that caught fire and burned down Before the FD even showed up) where we would replace receps and fixtures on old AL romex. The Codes decision to ban the use of AL under #10 is most definitely the right call-even with new manufacturing in place since the 80s. AL that small is too easy to have issues.
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The NEC does not now, nor has it ever, had a prohibition on using aluminum circuit conductors of any size.
 
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