Can I use 2 black THHN wires for a 240v line?
The answer is yes you can run your 2 hots the same color and they can be any color except white, gray, or green. If your circuit is only 220. (240 in modern terms) you will also need a ground, the ground can be metallic conduit or if using pvc conduit a green is normally used. If you want to run anything other than 240v you will also need a neutral to set up a breaker panel. If this is a detached shed a ground rod will also be needed. With more info we can help you size the wires &amp; conduit based on the load and distance but more info will be needed to do that but Yes you can use 2 black insulated conductors.