Thread: how common is aluminum NM?

So, for my insurance surveys I'm supposed to look for aluminum NM. And I have. But it takes so long to try to read all the blurry, faint writing on old cables and I've never found it, and I'm just wondering
- how common is it?
- when was it most often used (and does that vary regionally)?
- is it a really big hazard?
- are there any "easy" ways to differentiate it from copper NM?

I only usually look around the CB panel. No time to investigate more thoroughly.

And here's silly question that I'm too embarrassed to give its own thread. Do they make multi-stranded wire because it can bend more without becoming brittle? Is there an electrical reason it's twisted? I guess that's 2 questions.

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- how common is it?
- very in some areas in some time frames

- when was it most often used (and does that vary regionally)?
- mostly in the 1970s

- is it a really big hazard?
- it can be

- are there any "easy" ways to differentiate it from copper NM?
- copper NM is copper color conductor
- aluminum NM is aluminum color conductor

I only usually look around the CB panel. No time to investigate more thoroughly.
- That is where to look: where it is in the neutral terminal bar and in the breakers.

hee hee, I know what the conductors look like. But I don't take the panel off. Big no-no in my job.

Hmm, very common and a big hazard. I'll have to see about what it's like here. Al NM in MN.

Originally Posted by Kristi Silber

hee hee, I know what the conductors look like. But I don't take the panel off.

Then you would need to look for AL or Aluminum on the NM outer sheath.

But you already said that was difficult to do or find.

I'm looking for the easy way out.

It's not so much that it's difficult, it just takes time. The fees they pay us for this work necessitate efficiency.

Originally Posted by Kristi Silber

hee hee, I know what the conductors look like. But I don't take the panel off. Big no-no in my job.

Hmm, very common and a big hazard. I'll have to see about what it's like here. Al NM in MN.

I'm not sure why your employer doesn't see fit to do the training so you can find where aluminum wire exists. If the sheath isn't exposed then you need alternative means to check.

The wiring here is an attempt to pigtail aluminum wire with copper using the wrong connectors and/or add a circuit with copper wire to an aluminum wired circuit. This particular house had about a dozen fires in the making. The switch in the top photo had the back melted so it fit comfortably around the cables and splices. The yellow wire nut insulation in the bottom of the lower picture melted off the exposed splice.

This is NOT an uncommon find with aluminum wire.

Yikes, those are some scary photos. So is it when copper meets aluminum that the big problems are? Higher current in the copper than the aluminum can handle?

"I'm not sure why your employer doesn't see fit to do the training so you can find where aluminum wire exists."

I work (indirectly) for insurance companies. I'm not particularly proud of that facet of my job, but nevertheless that's where I'm coming from when I talk about my duties.

Insurance is all about statistics. I look for obvious stuff. They know I won't find all the problems, and they make all kinds of assumptions based on the obvious stuff to build their statistical models and account for the unknowns. They don't want to spend extra money to insure or train field reps to deal with anything potentially dangerous.

Although I'm more than my job and here because I want to learn more than I need to do it (and contribute when I can!), I'm bound by different rules from you guys.

I would think the insurance company would train their people better so they had a better idea of the risk they were underwriting. If you are going to assume so much why not just assume the worst case for everything?

Originally Posted by Kristi Silber

So, for my insurance surveys I'm supposed to look for aluminum NM. And I have. But it takes so long to try to read all the blurry, faint writing on old cables and I've never found it, and I'm just wondering
- how common is it?
- when was it most often used (and does that vary regionally)?
- is it a really big hazard?
- are there any "easy" ways to differentiate it from copper NM?

I only usually look around the CB panel. No time to investigate more thoroughly.

And here's silly question that I'm too embarrassed to give its own thread. Do they make multi-stranded wire because it can bend more without becoming brittle? Is there an electrical reason it's twisted? I guess that's 2 questions.

http://www.cpsc.gov/cpscpub/pubs/516.pdf

[quote=Jim Port;181364]I would think the insurance company would train their people better so they had a better idea of the risk they were underwriting. If you are going to assume so much why not just assume the worst case for everything?[/quote]

Premiums would be way too high and policyholders would switch companies.

We are trained to photograph fuse boxes/control panels, record the types of cable we can see, determine or at least estimate the age of the panel and any repairs/renovations to it, and look for externally visible signs of hazards, such as missing CBs in a panel, unprofessional-looking wiring, overfusing, inadequate amperage, missing faceplates, etc. Along with dates the "risk" and additions, if any, were built, underwriters can assess statistical likelihood of problems. The reasoning, I suppose, is that training, insuring and paying us to do more thorough investigation doesn't add enough data to make it cost-effective.

Bruce - thanks for the link! That's good information to have, helps me understand it all and know what to look for (didn't even know there was Cu-clad Al cable!). I'd wondered whether there were different gauges used for Al cable.