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I have a house that has several ungrounded circuits that uses the older 2 wire romex (pvc insulation, black woven jacket).

I'd love to have AFCI protected circuits for the bedrooms, and grounded outlets for some other rooms, but I don't want to have somebody rip the old cable that runs horizontally between the outlet boxes (also don't want to attempt that myself).

Would this be a proper procedure for replacing ungrounded circuits? I was thinking something like:

  • Disconnect old circuit
  • Take out old boxes, put bigger rework boxes in (current boxes are small)
  • Drill new hole up from basement under boxes
  • Fish wire up, secure in box with tab/clamp and with staple in basement*
  • Connect each outlet run for the room together with a junction box*
  • Run to panel*

*Assuming proper support according to 334.30

I also had a question with regards to NEC 334.30(B)(2):

334.30 Securing and Supporting Nonmetallic-sheathed cable shall be supported and secured by staples, cable ties, straps, hangers, or similar fittings designed and installed so as not to damage the cable, at intervals not exceeding 1.4 m (4 1⁄2 ft) and within 300 mm (12 in.) of every outlet box. junction box, cabinet, or fitting. Flat cables shall not be stapled on edge. Sections of cable protected from physical damage by raceway shall not be required to be secured within the raceway.

(A) Horizontal Runs Through Holes and Notches. In other than vertical runs, cables installed in accordance with 300.4 shall be considered to be supported and secured where such support does not exceed 1.4-m (4 1⁄2-ft) intervals and the nonmetallic-sheathed cable is securely fastened in place by an approved means within 300 mm (12 in.) of each box, cabinet, conduit body, or other nonmetallicsheathed cable termination.

FPN: See 314.17(C) for support where nonmetallic boxes are used

(B) Unsupported Cables. Nonmetallic-sheathed cable shall be permitted to be unsupported where the cable:

(1) Is fished between access points through concealed spaces in finished buildings or structures and supporting is impracticable.

(2) Is not more than 1.4 m (4 1 ⁄2 ft) from the last point of cable support to the point of connection to a luminaire or other piece of electrical equipment and the cable and point of connection are within an accessible ceiling

  1. Does 334.30(B) allow for this type of installation?
  2. Would 334.30(B) allow for a fished dropwire from an attic, with an unsupported vertical "run" of more than 4.5 feet down to an outlet box?
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It's better to use the device box as a junction point, rather than having all the cables spliced in a single junction box. Star topology doesn't work well in electrical wiring. You'll end up with huge junction boxes (box fill), and using terminal blocks instead of twist-on wire connectors. Also, using the tab clamps on plastic boxes as the only support method is not usually a good idea. –  Tester101 Dec 5 '13 at 10:33
    
What is the goal of this project, why are grounding conductors required? Neither Arc-Fault Circuit Interrupters (AFCI), nor Ground-Fault Circuit Interrupters (GFCI) require grounding conductors. –  Tester101 Dec 5 '13 at 10:38
    
@Tester101 Its two-fold 1. I'd like to AFCI's on the bedroom/living room circuits (sounds like I can do this already so +1) 2. I'd like to have a few grounded outlets for things that require long term use of a three-prong plug. The boxes are tight already without a GFCI outlet. –  Alex Moore Dec 5 '13 at 15:52
    
Based on your comments I will not do the star-topology replacement in the bedrooms. I do have a few outlets that have direct runs from the basement with nothing else in the series, so I may replace one of those in the future if needed. –  Alex Moore Dec 5 '13 at 15:56
1  
This answer might be helpful. –  Tester101 Dec 19 '13 at 12:28

2 Answers 2

up vote 1 down vote accepted

Before going through all that I'd check:

  1. If the existing metal boxes are already grounded (See How should I connect to a short ground wire in a metal box? and maybe Should old knob and tube wiring be replaced? )
  2. If the old cables will come out cleanly from below. Fish a string as you yank out the old cable.

Note:

  1. The NEC's unsupported rule does not apply inside walls. You get a free pass on that one.
  2. You can put an AFCI breaker on the two wire circuits, no problem.
  3. You can put a three prong GFCI on the two wire circuits, as long as they are labeled as such.
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Thanks! I'm going to put GFCI's as the first outlet in the series and replace the remainder with Tamper-Resistant 3-prongs with the appropriate stickers. Also going to put in AFCIs. Looking forward to make this house safer. –  Alex Moore Dec 6 '13 at 13:32
    
Caution: unless the chain has three wires, your first GFCI won't protect the chain of outlets. Install a GFCI at each location. Or just be happy with the AFCI on the chain (and install a real grounded outlet for anything near water). –  Bryce Dec 8 '13 at 8:58

I seem to recall (not from a handy chunk of code, just from talking with an electrician I work with sometimes) that abandoning wire is generally a no-no (not sure if that applies when it's inaccessible and impractical to remove, which might make the exception.)

Fishing wires up or down exterior walls that have insulation in them will be potentially frustrating, to say the least.

334.30(B)(1) would appear to allow this, and 334.30(B)(2) only says it applies in accessible ceiling spaces. 334.30(B)(1) (an inaccessible, impractical to support space in an existing finished structure that wire is fished through) appears to apply, without a specific length limit. But they don't get a lot of points for clarity.

If you are opening up to put in larger boxes, you may be able to staple the ends of the cables before you set the box (reaching through the box hole.) Doing so won't really buy much though, since that end will be supported at the box. You definitely want to fish the wire before you set the new box.

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Old house, no exterior wall insulation. Usually sucks but in this situation it seems to be a boon. –  Alex Moore Dec 5 '13 at 3:16
    
What I prefer doing with abandoned wires that I can't remove is to twist the conductors together so that it can never be energized. I also connect one end to ground. –  Brad Gilbert Dec 6 '13 at 20:32

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