Aluminum strand branch wiring

[Mike Lamb]

Should aluminum strand branch wiring be called out the same as single wire aluminum? I read on at least one site that was okay but I don't know if that is credible information. I have called for panel replacement. Should the aluminum branch circuit wiring also be called out? The circuit is for a wall AC unit.

 

[Marc]

No. Stranded aluminum wiring, even when its the original formulation, was able to make good connections with terminals intended for copper. I wouldn't write it.

[Bill Kibbel]

No issues I know of with stranded aluminum, if it's a home run and starts and ends at AL labeled terminals.

[Marc]

Before aluminum, electrical connectors were engineered and intended for metallic copper. When aluminum came along, it quickly became evident that the same connectors didn't work as well with solid aluminum conductors. The issue was found to be a result of the reduced malleability of the aluminum compared to copper. It didn't deform as well, which resulted in poor connections, excessive voltage drops, and thus excessive heat.

There were other issues but this one got the most attention.

The solutions were an alloy of aluminum, as well as re-engineered connectors that were able to develop the compressive force needed to make good connections on both copper and the new aluminum alloy.

Just my take on it.

Edited October 13, 2023 by Marc

[Jim Baird]

1 hour ago, Marc said:

Before aluminum, electrical connectors were engineered and intended for metallic copper. When aluminum came along, it quickly became evident that the same connectors didn't work as well with solid aluminum conductors. The issue was found to be a result of the reduced malleability of the aluminum compared to copper. It didn't deform as well, which resulted in poor connections, excessive voltage drops, and thus excessive heat.

There were other issues but this one got the most attention.

The solutions were an alloy of aluminum, as well as re-engineered connectors that were able to develop the compressive force needed to make good connections on both copper and the new aluminum alloy.

Just my take on it.

Thanks for continuing your reply, Marc.

My understanding of AL single strand was that its increased malleability in response to ebb and flow of current led to diminished connective surfaces that generated dangerous levels of heat.  I did not think of copper responding to ebb and flow and keeping enough contact to keep things safe.

We still don't have a suitable AL alloy for single strand branch, do we?

[Marc]

2 hours ago, Jim Baird said:

Thanks for continuing your reply, Marc.

My understanding of AL single strand was that its increased malleability in response to ebb and flow of current led to diminished connective surfaces that generated dangerous levels of heat.  I did not think of copper responding to ebb and flow and keeping enough contact to keep things safe.

We still don't have a suitable AL alloy for single strand branch, do we?

The problem was never the wire, just the connectors. Re-engineering the connectors was combined with a more malleable alloy of aluminum to get a finished solution.

I don't ever recommend replacement of electrical wiring. I do recommend that both ends of every single length of aluminum wire be connected with devices intended for CU/ALR. It's labor intensive but so is total replacement of all wiring, especially after interior finishes are repaired, once the sparky is done.

[Jerry Simon]

2 hours ago, Marc said:

I don't ever recommend replacement of electrical wiring. I do recommend that both ends of every single length of aluminum wire be connected with devices intended for CU/ALR. It's labor intensive but so is total replacement of all wiring, especially after interior finishes are repaired, once the sparky is done.

I always have recommended replacement.  It's way too easy for a well-meaning homeowner to replace a receptacle/switch of some sort with one not compatible.

[hausdok]

That label is marked CU-AL, so I would have been more interested in what it was connected to at the other end. So many electricians seem to ignore or overlook that. In my own place, about five years ago, I lost power to a bunch or receptacles. When I pulled the cover on the panel, I found the electrician who wired the place in 2005 had ignored the rules and the bus was burned through. Needed a new panel and it was less than 15 years old!

[John Dirks Jr]

Another thing to consider is differences in how the multi strand and single strand conductors are used.  The multi strand stuff most often begins at one device and ends at another and that's it.  The single strand branch AL intersects many devices all over that house.   Since the problem is mostly happening at connections, there are many more incidences with the single strand stuff because there are many more connections to devices.  Statistically with regard to recorded problems, one product escapes scrutiny while the other is deemed problematic.

[Jim Katen]

On 10/13/2023 at 5:26 AM, Marc said:

Before aluminum, electrical connectors were engineered and intended for metallic copper. When aluminum came along, it quickly became evident that the same connectors didn't work as well with solid aluminum conductors. The issue was found to be a result of the reduced malleability of the aluminum compared to copper. It didn't deform as well, which resulted in poor connections, excessive voltage drops, and thus excessive heat.

There were other issues but this one got the most attention.

The solutions were an alloy of aluminum, as well as re-engineered connectors that were able to develop the compressive force needed to make good connections on both copper and the new aluminum alloy.

Just my take on it.

That's the gist of it but with one exception. Aluminum is *more* malleable than copper, so it deforms more readily under pressure from a lug. (Which is why you shouldn't "re-torque" aluminum connections.) The old, 1960s aluminum alloy also suffered from "creep" or "cold flow," a property related to its malleability. This (along with the crappy old stab-back connections popular at the time) was what resulted in loose connections that caused fires. Connections made with old aluminum alloy and the old receptacle and switch screws would loosen over time as a result of the aluminum creeping under pressure, especially under cycles of pressure resulting from the different coefficients of expansion between the aluminum and the screw connectors.  Modern AA-8000 aluminum alloy wiring doesn't creep under pressure anywhere near as much as the old alloy and modern screw connections at the switches and receptacles are far more compatible with aluminum. 

It's also worth noting that the designation of CU/AL is fine on breakers, but for switches and receptacles you want to see CO/ALR - the revised designation for aluminum-compatible devices. 

As for Mike's original question, stranded aluminum wire never experienced the same problems because the expansion/contraction cycles and the "creep" phenomenon were distributed over many small strands instead of over one larger one and the overall integrity of the connection didn't suffer as much as a result. 

And to answer Jim's question, the AA-8000 alloy would work just fine for branch wiring today (you can still buy it in solid #8), but no one makes it in #10 and #12 because it's just a tainted product. 

 

[John Kogel]

Speaking of stranded AL here's why bare stranded aluminum is not acceptable for connection to a grounding rod. At least that is the Canadian rule, must be copper.

I had rigged up a subpanel in a shed on the edge of a patch of bush, and for the grounding, I used a loose chunk of bare Al stripped from a length of used triplex, the typical overhead feeder of 3 cables twisted together. About 10 years later, The bottom end was buried in damp leaves and debris. The end of the cable under the leaves had rotted completely away.

[Jim Baird]

On 10/14/2023 at 2:32 PM, Jim Katen said:

That's the gist of it but with one exception. Aluminum is *more* malleable than copper, so it deforms more readily under pressure from a lug. (Which is why you shouldn't "re-torque" aluminum connections.) The old, 1960s aluminum alloy also suffered from "creep" or "cold flow," a property related to its malleability. This (along with the crappy old stab-back connections popular at the time) was what resulted in loose connections that caused fires. Connections made with old aluminum alloy and the old receptacle and switch screws would loosen over time as a result of the aluminum creeping under pressure, especially under cycles of pressure resulting from the different coefficients of expansion between the aluminum and the screw connectors.  Modern AA-8000 aluminum alloy wiring doesn't creep under pressure anywhere near as much as the old alloy and modern screw connections at the switches and receptacles are far more compatible with aluminum. 

It's also worth noting that the designation of CU/AL is fine on breakers, but for switches and receptacles you want to see CO/ALR - the revised designation for aluminum-compatible devices. 

As for Mike's original question, stranded aluminum wire never experienced the same problems because the expansion/contraction cycles and the "creep" phenomenon were distributed over many small strands instead of over one larger one and the overall integrity of the connection didn't suffer as much as a result. 

And to answer Jim's question, the AA-8000 alloy would work just fine for branch wiring today (you can still buy it in solid #8), but no one makes it in #10 and #12 because it's just a tainted product. 

 

"tainted" as in bad rep, bad record?

[Bill Kibbel]

4 hours ago, Jim Baird said:

"tainted" as in bad rep, bad record?

Besmirched.