SQLit said:
Al is used every day by every utilitiy in the US. Here in Phoenix every new house with a circuit over 30 amps has AL conductors.
Service entrance conductors connections use Aluminum rated lugs and connectors and an antioxide paste. Branch circuits are more problematic.
CU to AL connections, wire nuts has been the standard for some time IF you can not get the AL- CU devices. My home has AL circa 1971 and pigtails on some devices and AL-CU devices every where else. Most AL devices do not have a "stab in"connection. They use screws for the connection. Finding the devices at a decent price is the real trick. That is why people pigtail.
A tight connection is necessary with AL. Wirenuts when twisted together properly are acceptable.
I agree that wirenuts should be reliable if they are rated for aluminum and copper.
Aluminum connections have 2 problems.
Aluminum expands more than most metals. When an aluminum wire in a lug made of another metal conducts current it gets warm and expands and it may be compressed in a lug that does not expand as much. This makes the connection looser with a higher resistance so on the next heating cycle it gets a little hotter and looser. Lugs used with aluminum should be listed for this use as referenced above with CuAl devices. I would trust a wirenut more than a device if the wirenut has a "live spring" that deforms when twisted over the wires and maintains a spring compression on the connection.
The second problem is that aluminum is very reactive. A clean surface will rapidly oxidize. This keeps the aluminum shiny since aluminum oxide is clear, but aluminum oxide is an insulator. This problem is solved by coating the conductor surface with a paste made for this purpose. A common one is Noalox (no-aluminum-oxidation). I would suggest coating the wire before wirenuting it.
Note that these problems can occurr at any aluminum connection including original wirenut connections and at connections to circuit breakers.
This is the third home I have owned with AL wiring.
Do you know anyone who owns a meggar? You can test the circuits one by one or the whole house at once. (power off NOTHING plugged in). Some one who is familar with a meggar can tell you if you have any problems with the insulation. I have even found loose connections using a meggar.
A megger measures high resistances using a relatively high voltage. In this case I presume you would be measuring the resistance to ground. I don't see how this would find problems or loose connections unless there is a carbon path to ground. A megger will probably destroy GFCIs.
Bud--
