Electrical problem -Termininating a live wire

What is the best way to terminate a live wire? I want to rewire a box that has 2 wire ungrounded romex with 12-2w/g. The problem is the box is currently recieving power from a box in an unknown location hidden under an attic floor and cannnot be disconnected. I could possibly put wire nuts on the existing wire in the existing box but that would leave the box very crowded. Any suggestions?
On another another circuit, I found the source but am not able to physically remove the disconnected wires from the box. Can I just cut off the disconnected wires or would it be better to put wire nuts on them?
Art
To me, the phrase "America, Love it or leave it" is not very patriotic. Anyone can express the same exclusionary sentiment about thier country. I would rather say, "America, Love it or Change it".
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Arthur Queen wrote:

The best way, as you already mentioned, is to locate the source and disconnect. It would be worthwhile to take apart any outlets and junction boxes in the area to look for it. If the source is in a junction box that is no longer accesible because somebody built a floor over, the next best thing is to terminate the existing wires in the box. (An inaccessible wiring box, incidentally, is a code violation, but not exactly astonishing.) Wire tracing equipment is available for around $100. You might be able to rent or borrow this equipment.
The space taken up by the wires can be reduced by terminating them with small wire nuts just big enough for one wire. Cut out any extra cable sheath or paper cable packing, if the installer left extra in the box. Leave the leads just long enough that test equipment could be connected in the future, about six inches if you can manage it. Tape will take up even less space, but I think the wire nuts are better.
Consider replacing the box with a bigger one.

If you can absolutely determine that you have located and disconnected BOTH ENDS of the same cable, and have made it IMPOSSIBLE to reconnect either end, you can cut it off. Otherwise, the wire nuts would be much better.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 16 Feb 2004 02:20:25 GMT, Anthony Straight

GANG BOX - not GANG BANG
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.