I recently ran across this with a fellow NACHI inspector, I have never seen this before. It is in a sub-panel the solid aluminum ground conductor has been extended by using a wire nut to add a section of stranded copper to get it long enough to connect to the ground bus bar. Would this be considered improper and if so why? I can’t find much other than dissimilar metals. I thank you for your replies.
Here’s what the NEC says about dissimilar metals. What was the bare aluminum conductor being used for?
110.14 Electrical Connections. Because of different characteristics of dissimilar metals, devices such as pressure terminal or pressure splicing connectors and soldering lugs shall be identified for the material of the conductor and shall be properly installed and used. Conductors of dissimilar metals shall not be
intermixed in a terminal or splicing connector where physical contact occurs between dissimilar conductors (such as copper and aluminum, copper and copper-clad aluminum, or aluminum and copper-clad aluminum), unless the device is identified for the purpose and conditions of use. Materials such as solder, fluxes, inhibitors, and compounds, where employed, shall be suitable for the use and shall be of a type that will not adversely affect the conductors, installation, or equipment.
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Guaranteed galvanic corrosion of the dissimilar metals–the splice will fail at some point.
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Here is some good information
https://inspectapedia.com/aluminum/Aluminum_Wiring_Repair_Methods.php
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