[bottlerockett]

Hi all,

I'm a newbie attempting to replace knob and tube wiring in my attic for the overhead lights in my foyer, living room, kitchen, etc. Six lights in total (one is a ceiling fan) will be on one new, 20-amp circuit, using 12/2 wire. Each will have its own switch.

Can someone please describe for me the specifics of how to connect the wires for this setup? (e.g., "Connect the black from the panel and the black from the second switch box with the pigtail...")

I think I want to run power to the light fixture first, rather than the switch, since, in the attic, it seems like the easiest way to route the wires. Does that mean I need to splice three different wires at each light fixture (one from power, one to switch, one to the next light)?

I keep referring back to this thread and the great answer from Chris, which shows how to do this when you run power to the switch first:

http://answers.yahoo.com/question/index?qid=20110314050322AAaeWgQ

But again, seems like running power from switch to switch will create more of a maze of wires in my attic. Is one method better than another?

Just hoping someone can explain the detailed wiring setup for this scenario. FYI, I already understand the basics and code on how to route wires in the attic (been reading my Home Depot wiring manuals, plus lots of other forum threads). Thanks in advance.

Don

 

[joed]

You can't do what you want with 12/2 cable. You would need some 12/3 cable. Unless you want to go buy some 12/3 cable you will need to go to the switch first.

 

[bottlerockett]

Hey, thanks joed. So regarding power-to-switch vs. power-to-light-fixture... is one method more common, or more preferable to the other for any reason, in an attic scenario?

Don

 

[sirsparksalot]

The attic setting has nothing to do with it. Personally, I go to one of the switches first, because it's easier for me to grasp.

I read the link you provided, and it appears correct.

 

[sirsparksalot]

BTW: 14/2 (instead of 12/2) is good if you haven't already bought the 12 AWG

 

[thadsaab]

BTW: 14/2 (instead of 12/2) is good if you haven't already bought the 12 AWG

Only if he also makes this a 15 amp circuit instead of 20 amp.

 

[joed]

Hey, thanks joed. So regarding power-to-switch vs. power-to-light-fixture... is one method more common, or more preferable to the other for any reason, in an attic scenario?

Don

The way that uses the least cable is the way I do it. Of course there are new code rules requiring neutral wires in the switch box so switch first often becomes the way.

 

[bottlerockett]

Hey, thanks all. I'll wire it switch to switch. Went up in the attic and the routing makes sense to me. What's great is that there are already holes in the joists where the current knob and tube runs, so I'll have very little drilling to do.

 

[bottlerockett]

Hey all,

I'm in the middle of this job, and it seems like I can't possibly cram all the wires I'm using into a normal switch box, and still be up to code. Can you help? How would you do this? To refresh, I'm rewiring the overhead lights in my house on a new circuit, replacing knob-and-tube. In each switch box there are three separate runs of 12-2 Romex (from power, to light fixture, to next switch).

I just did this for one light and I had to pack the wires into a normal metal switch box (3"x3 1/4"). It was hard, especially since I left each wire 8" long. By my calculation, that's 10 wires in the box (6 insulated wires, 1 for ground, 2 for the switch, 1 for metal cable clamps), which seems to be too many for any single-switch box.

What should I be doing here to be in code compliance? Fitting wires in a larger two-gang switch box, but the second half of it is hidden behind the plaster wall? I'm confused. Any guidance appreciated.

 

[sirsparksalot]

You need a 22.5 cu. in. switch box. They come in single gang. Carlon makes th plastic Blue box: B122A
http://www.carlon.com/Installation_Training/IT-Choose_Wiring_Box.pdf

 

[bottlerockett]

Ah, thanks! Didn't know they made a single box that big. Cool.

One more question: Since the plastic boxes don't have wire clamps at the back (just pop-through ports for each run of Romex), does code require me to fasten the wire cables in some other way, to a stud behind the wall or something? so there's no possible tension on the wires in the box.

 

[sirsparksalot]

One more question: Since the plastic boxes don't have wire clamps at the back (just pop-through ports for each run of Romex), does code require me to fasten the wire cables in some other way, to a stud behind the wall or something? so there's no possible tension on the wires in the box.

yes, it should have the first staple (I believe) within 6" from the box.

 

[SD515]

Fastening required within 8" if the box doesn't have clamps, 12" if the box has clamps.

 

[sirsparksalot]

Fastening required within 8" if the box doesn't have clamps, 12" if the box has clamps.

Kyle, I tried to find this in the Code, but couldn't. All I could find is the exception listed in 314.17 (C) Nonmetallic Boxes and Conduit Bodies, but that references UF cable. I know it's there, where in the Code can I find this?

 

[Jim Port]

Try 334.30 also. The 314.17(C) exception lists both UF and non-metallic cables into single gang boxes non-metallic boxes. If a metallic box was used it would be clamped.

 

[sirsparksalot]

Try 334.30 also. The 314.17(C) exception lists both UF and non-metallic cables into single gang boxes non-metallic boxes. If a metallic box was used it would be clamped.

NEC 334.30[/b]]

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 (41⁄2 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.​

Thank you, Jim. So, according to this, an NM box (with no clamping device) needs to be secured within 12" (not 8" or 6") of the box, and then every 4-1/2' thereafter?​

​

​

​

​

​

 

[sirsparksalot]

Oh, wait a min. This is cable support. For NM box support, 314.17(C) applies?

 

[bottlerockett]

Guys, another round of thank yous. This is invaluable to me, and I've realized that I need to more or less start this project over, and rip out the too-small switch boxes, and even re-thread new Romex through the walls, because the wires I mashed into the switch boxes probably won't be in good shape to reuse.

I'm not an electrician, so I feel like I need to follow the letter of the code and not cut ANY corners and risk any issues down the line. Was also not aware that cable needed to be stapled behind walls, but I guess it makes sense -- stapling every four feet, whether its across a joist or down a wall. Any tips for more easily stapling Romex behind a finished plaster/lathe wall? I guess I'll just cut a bigger hole in the plaster so I can squeeze a hammer in there.

 

[sirsparksalot]

Guys, another round of thank yous. This is invaluable to me, and I've realized that I need to more or less start this project over, and rip out the too-small switch boxes, and even re-thread new Romex through the walls, because the wires I mashed into the switch boxes probably won't be in good shape to reuse.

I'm not an electrician, so I feel like I need to follow the letter of the code and not cut ANY corners and risk any issues down the line. Was also not aware that cable needed to be stapled behind walls, but I guess it makes sense -- stapling every four feet, whether its across a joist or down a wall. Any tips for more easily stapling Romex behind a finished plaster/lathe wall? I guess I'll just cut a bigger hole in the plaster so I can squeeze a hammer in there.

Two thumbs up for doing this by Code (especially recognizing that since we don't do this every day like the pros here, we need all the help we can to make things safe). Don't try and cut corners, cause that's when, inevitably, we mess up. The pros here are great, so don't be shy about asking.

If you're working in old work (plaster and drywall is already up), then what you need to do is find some "old work" boxes. These come with ears that are adjusted behind the wall by adjusting a screw. They are plastic PVC boxes, and you should be able to find them at the Big Box stores like Home Depot and Lowes.

As far as securing the cable, again if it's behind walls that are already up, NO, you don't have to secure them. BUT, you do need the boxes that have plastic clamping devices attached. No need to tear up your walls trying to get a hammer in there.

I may have missed the fact that this is old work, assuming that you had open walls. If I did, apologies.

 

[Jim Port]

The cable needs to be secured within 8" if there is no clamping at the box, otherwise with clamps it goes to 12". Most plastic single gang boxes do not have clamps.