I am replacing a 20 year old wall oven. When I opened the electrical box I noticed very large gauge aluminum wiring (6 gauge?). I purchased a box of AlumiConns (3 port style) to connect the aluminum wiring to the 10 gauge copper wire in my new oven.
Can I simply untwist a couple aluminum strands from the larger bundle? I plan to insert two aluminum strands into two ports on my AlumiConn and the 3rd port will go to the oven's copper wire.
Note in the 2nd photo below that there was no anti-corrosive paste inside the wire nuts. I was a little surprised how well this 20 year old connection stood the test of time, the wire nuts showed no sign of getting hot and the old copper and aluminum wire looked fresh. I'd still like to update the connection to current code and not have to worry about a future electrical fire decades from now.
Best Answer
Use a mechanical lug connector ("Polaris" or equivalent)
AlumiConns are only rated for a maximum of 10AWG wire. For fatter work, you'll want their bigger brothers, mechanical lug connectors (sometimes called "Polaris connectors" after a common brand name) -- the smallest size of them is generally rated for wires anywhere from 14AWG to 4AWG, and as a rule, they are dual-rated for aluminum and copper wire.
You will also likely need a box extension ring or two, as mechanical lug connectors are quite chunky compared to wirenuts or Alumiconns, and you definitely need an appropriate connector to attach the flexible conduit to the box, as right now, it's violating several Code sections by flapping around in the breeze like that. If the extension rings aren't enough, then you'll have to replace the box with a small (6" by 6" by 4" should be ample) NEMA 1 (indoor) pull box, likely with a flush cover. These are what is used instead of a junction box when splicing large wires, and are available through electrical supply houses.