I recently ran a cat-6 cable from inside my house to the office, and I bought a bulk box of 500 feet. I pulled lots more out of the box than I ended up needing, and so now I have about 100 feet of cable outside the box.
Is there an electrician’s secret trick to getting the cable back into the box?
Don't
Just coil it up and tape it to the side of the box. Then put the box away, or sell it, depending if you have any future need for cable. The coiling interior to the box to make them work is more complex than it appears on casual inspection, and getting the box tangled so it won't "just pull out" is far worse than having some coiled cable on the outside. How do I know? 300 feet of miserably tangled cable in a box that I had to fight with until I used it up, got a new box, and NEVER tried that foolishness again. Network wiring is part of what I do for a living.
Depending on the particular box, there are two problems:
Pushing cable in from the outside will end up with a tangled mess.
With some boxes, the output hole isn't just a hole but a plastic piece that "bites" the cable in one direction to prevent it from slipping back into the box.
The solution is to:
Open the box on one side. That will allow you access so that you can pull the cable in and loop it the same way as the rest of the cable to prevent tangles and allow you to pull it out normally in the future.
If there is a plastic piece that "bites", carefully remove it from the box. Depending on how it is designed, you may be able to put it back afterwards. But if you can't put it back, leave a couple of feet of cable out of the box and tie them in a simple knot to prevent the end of the cable from slipping into the box. (That's what cables like to do in the back of the truck when you're not looking.)
Very often it just isn't worth the hassle - if it is < 50 feet then why bother opening up the box, removing the plastic piece, etc. And if it is > 50 feet then do you really want to sit there coiling it up "just so" instead of an easy coil outside the box. But if you do that, use a cable tie instead of tape. You should have cable ties around anyway for securing cables neatly in various places, and that way when you are ready to use the extra cable, just snip the tie open and you're all set - as opposed to dealing with removing the tape and dealing with sticky adhesive on the cable.
Coil it up around hand to elbo, flatten the coil and stick it in the hole. Then when you are ready to use it, just pull it out. Don't try to re-coil it in the box., it's like trying to respool yarn.
I can only suggest opening one side of the box and turning the roll of cable inside - this will not be easy unless the tube the cable is on rotates as well...
Once all is back inside, stick the side back.
I was taught to coil the extra cable around the box and put the end into the hole. Never had a problem with knots.
