I have a 200 amp main panel that is nearly full and I plan on adding a 100 amp subpanel close by in the basement of my residence (south-east PA). I happen to have some wire available that I believe is adequate gauge (based on reading many other posts) but I want to make sure the specific wire I have is reasonable to use. The wire I have is 3 individual copper wires labeled: “54488 2AWG 600V MTW OR THHN OR GASOLINE & OIL RESISTANT OR AWM (UL)” plus one green ground wire labeled “8AWG TYPE THW 600V VINYL THERM CERRO-VW-1 (UL)”. Is this adequate to connect from the main panel with a new 100amp breaker added to a subpanel which has a 100 amp main breaker. The three main conductors of this wire all have black insulation – is it acceptable to use colored electrical tape to mark the white and red lines? Since these are individual conductors and even though the panels are just a few feet apart in the basement , I’m guessing I still need to use conduit. Correct? Which type(s) are acceptable (PVC, metal, flex, etc)?

If this wire isn’t reasonable to use in this application, I will probably scale back to a 60amp breaker in the main panel and use an easier to get appropriate gauge copper wiring. The subpanel is there to handle additional new outlet and light circuits for my basement and sunroom that won’t fit in the main panel.

Thanks in advance for your guidance.

The wire size you have is fine for 100 amp. Colored tape is acceptable to mark wires. All the conduits you mention are acceptable, use the one that fits and installs the best for your situation.