220v help PLEASE

[Dommer66]

Ok I’m not electrician, just trying to save money. And just wanna get some input before I continue.

I added a 20a breaker to my circuit box, ran 10/3 to a 220 outlet.

Hots to my X and Y, neutral and ground all went to this outlet. 2 hots to the 20a, and my neutral and ground to the spot in the box for them. I had to join two rolls of wire together with wire nuts in the attic.

I was just about done, cleaning up. And after I tested the outlet with my meter. Went to push it back into the box, and POOF. Bright flash and a pop and it was smoking. Like I said it tested fine on the meter and I didn’t have a problem till I tried to push it into the outlet box. I had all my wires screwed down tight as I could, I triple checked. If anyone has any idea what I could’ve done wrong please let me know.
If it makes a difference this is to power a tanning bed for my mother in law. But I didn’t even get to plug it in like I said. -TIA-

 

[westward10]

You pushed it back into the box whilst it was still live?

 

[DanMcLiverpool]

I'm not an electrician so this is purely a question for my sake - what did you test? I'm guessing the faceplate of a socket? And then tried to screw that faceplate back into the back box (note: I'm UK-based, language might be a bit different)?

 

[Megawatt]

I'm not an electrician so this is purely a question for my sake - what did you test? I'm guessing the faceplate of a socket? And then tried to screw that faceplate back into the back box (note: I'm UK-based, language might be a bit different)?

I know this is old but as stated above you pushed it in live and somehow the bare ground touched the live screw