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I need to add a wall receptacle in a bedroom. (There aren't enough outlets as is.) The bedroom is on the main floor of a 1-story house, with an unfinished attic and an unfinished basement. Walls are old, plaster and lathe. The receptacle would essentially get added on to the end of the circuit that powers the other receptacles in the room.

The NM cable for that circuit already runs under the floor, easily accessible via the basement, and then up through the floor to each receptacle. (This was done when replacing old knob & tube wiring, which is why the cable doesn't just run through the walls from receptacle to receptacle, which would have required a whole lot of damage to the walls.) The cable to the new receptacle will also need to run under the floor, and then up through the wall to the new receptacle.

Is it better to:

  1. Tie into the cable in the basement, under what is currently the last receptacle, using a junction box (and then over and up to the new receptacle)? or
  2. Tie into the cable in what is currently the last receptacle (daisy-chain), and then run the new cable back down into the basement (and then over and up to the new receptacle)?

On a general level, the question is: when adding a new receptacle, is it better to daisy-chain when possible, or just use a junction box?

My assumption would be that it doesn't matter. As long as the receptacle is large enough to accommodate the additional wiring, then go with daisy-chain; otherwise, use a junction box. But maybe there's something else I need to consider? The daisy-chain method in this case would require an extra 2ft or so of cable, but I can't imagine that's an important factor.

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If you have enough wire to have 6" from the back of the junction box where you tie in a junction box would be the easiest way. Most of the time the wires are tight. then there are 2 options. #1 to pull the wire down from the outlet to your box using the wire to pull a string or the new NM cable down to the box some times the easiest is to pull a string when pulling the NM down then use the string to pull the new NM up. #2 Option would be to pull into the existing box from downstairs this can be a challenge getting the NM into the outlet box (if there is enough room in the box to make the junction). I usually use #1 It cost a few dollars more but saves in time trying to fish wires in a closed wall.

  • I think I understand. You're saying if the cable has enough slack, then a junction box may be easier since it will avoid any hassle with fishing wires through the wall. That makes perfect sense, and it's probably the way I'll go. That said, aside from cost, is there any reason to avoid using junction boxes in a situation like this? Are they for any reason less safe, for example, then a daisy-chained receptacle? (I hope I'm using the term "daisy-chain" correctly...) – PhilPDX May 27 '16 at 21:21
  • It is easier to do the junction box and just as safe. It may cost a few dollars mor for the box but it saves 30-60 minutes in a closed wall so that is the way I do it almost all the time. – Ed Beal May 28 '16 at 0:14
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I would try to keep junction box use to a minimum.

Sure when you first install a junction box you know where it is and what it does and it's readilly visible.

But then over the years it gets covered with dust and dirt and possiblly hidden behind/under something or even sealed into the building (your electrical rules may require junction boxes to be accessible but if you expect every other tradesman and diyer to know and respect that you are living in a fantasy world). The original installation paperwork (if any) inevitablly gets lost.

So suppose years later a joint goes bad and some sockets stop working. If the joint is at an outlet on the circuit the electrician can easilly find and fix it. If the joint is in a junction box somewhere expect hours of searching.

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