Aluminum romex splices and devices

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jaylectricity

jaylectricity

Senior Member
Location
Massachusetts
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licensed journeyman electrician
I was always under the impression that you can't tie copper and aluminum together but I'm replacing devices in an old house with almost all copper conductors. But there have been a few places where it was aluminum cable 12AWG.

One switch just had the copper feed on one terminal and the aluminum load on the other terminal. It was a regular switch.

A couple of receptacles had a copper pigtail spliced under a regular red wirenut with an aluminum conductor. The copper terminated on the device.

These have been installed for quite awhile. They were grounded receptacles, but flat-head screws installed on metal boxes. I'm guessing at least 20 years ago.

I do not see a single sign of corrosion, heating or any other sort of damage.

What gives?
 
jaylectricity said:
I was always under the impression that you can't tie copper and aluminum together but I'm replacing devices in an old house with almost all copper conductors. But there have been a few places where it was aluminum cable 12AWG.

One switch just had the copper feed on one terminal and the aluminum load on the other terminal. It was a regular switch.

A couple of receptacles had a copper pigtail spliced under a regular red wirenut with an aluminum conductor. The copper terminated on the device.

These have been installed for quite awhile. They were grounded receptacles, but flat-head screws installed on metal boxes. I'm guessing at least 20 years ago.

I do not see a single sign of corrosion, heating or any other sort of damage.

What gives?
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None of what you describe is safe or compliant. If you need to attach AL wire to a device it must be rated and marked COALR (they are available) or use CU pigtails spliced to the AL with an approved CU/AL connector.
 
texie said:
None of what you describe is safe or compliant. If you need to attach AL wire to a device it must be rated and marked COALR (they are available) or use CU pigtails spliced to the AL with an approved CU/AL connector.
Click to expand...

You aren't saying anything that I wasn't implying. You are correct in your recitation of the rules.

What I was expecting to see was evidence of unsafety.

Shouldn't the wirenuts have been melted, or overflowing with corrosion?
 
jaylectricity said:
Or a more simple question:

What is the safety issue? What was supposed to happen that makes it unsafe?
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The safety issue comes from the loosening of the connection (which causes heating) over time by the constant heating and cooling of the connection do to loading and unloading, known as "creep". AL conductors prior to the mid seventies were more prone to this as the alloys used were not what they are today.

My guess, in your case, the circuits involved probably were not heavily loaded.
 
Yeah, it was poor workmanship all around the house. Guess they just got lucky. I'll just be using the proper devices to replace them.

Now what about connecting copper to aluminum at the service drop with split-bolt burndys?
 
jaylectricity said:
Yeah, it was poor workmanship all around the house. Guess they just got lucky. I'll just be using the proper devices to replace them.

Now what about connecting copper to aluminum at the service drop with split-bolt burndys?
Click to expand...

It would seem OK to me if it is a CU/AL split bolt with the spacer. By why would this not be the POCO's problem?
 
jaylectricity said:
I was always under the impression that you can't tie copper and aluminum together but I'm replacing devices in an old house with almost all copper conductors. But there have been a few places where it was aluminum cable 12AWG.

One switch just had the copper feed on one terminal and the aluminum load on the other terminal. It was a regular switch.

A couple of receptacles had a copper pigtail spliced under a regular red wirenut with an aluminum conductor. The copper terminated on the device.

These have been installed for quite awhile. They were grounded receptacles, but flat-head screws installed on metal boxes. I'm guessing at least 20 years ago.

I do not see a single sign of corrosion, heating or any other sort of damage.

What gives?
Click to expand...

i'm guessing that there wasn't much in the way of connected load on that portion of the circuit.
aluminum wire does very well when there isn't current flow... :p
 
jaylectricity said:
You aren't saying anything that I wasn't implying. You are correct in your recitation of the rules.

What I was expecting to see was evidence of unsafety.

Shouldn't the wirenuts have been melted, or overflowing with corrosion?
Click to expand...

jaylectricity said:
Yeah, it was poor workmanship all around the house. Guess they just got lucky. I'll just be using the proper devices to replace them.

Now what about connecting copper to aluminum at the service drop with split-bolt burndys?
Click to expand...
Most of your questions have been answered already. I want to add that aluminum and copper have a big difference in thermal expansion rates. Little or no load will mean little thermal expansion and the connections will remain in good condition over a longer time. Put regular heavy load on the connection and it will fail much faster as it is heated and cooled often and expands to a higher differential leaving the connection just a little looser when it contracts then it was before. Now keep repeating the process and it gets loose enough that some increased resistance develops in the connection - adding more heat and more expansion, ultimately it will have total failure at some point.
 
texie said:
I was going to mention those connectors, but then I noticed the OP was talking about a service drop. I thought he moved on from the device question. That is why I mentioned the POCO. Guess I'm confused.:)
Click to expand...

No matter where a thread goes, there's always going to be somebody that reads the OP then scrolls right down to the comment box.

It's all good.
 
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