The clamps I was talking about are inside the box and have one kind-of big screw. One clamp covers 2 holes, and there's one clamp at the top and one at the bottom of the box.
Someone else asked about the integral clamps in plastic boxes (a little tab where you push through the cable.) I wouldn't count those at all, but I would make sure I wasn't already right at (or over) the number of conductors.
Bob
It sounds like these are the only types of clamps that would count--internal metal clamps in a metal box. Or are there other examples of internal clamps? I've never added any clamp allowances in my calculations, and I want to be sure that I'm not supposed to.
On a semi-related note, if one uses an EMT conduit stub to protect NM cable that would otherwise be exposed to damage, is anything special (e.g. a bushing) required at the end of the conduit where the cable enters, or is it sufficient to deburr the conduit end?
Thanks, Wayne
Not only don't you count those, you can simply tear them out.
You don't need a clamp to enter NM cable into a plastic box, just a staple within 8" of the box. Many plastic boxes have no clamp at all.
I believe that only applies to single gang boxes.
FWIW, I've always seen them in double gang and bigger boxes, and never in single gang boxes.
Cheers, Wayne
On Mon, 4 Oct 2004 15:21:04 -0700, Wayne Whitney wrote (in article ):
Wayne -
Yes, those are the only type of clamp I've seen that requires a fill allowance. And, as Bob observed, you can and should remove unused ones.
Regarding sleeved NM: That would be up to the inspector (there is no specific code requirement), but IMHO, EMT would not require a bushing, just proper deburring as you suggest. However, Rigid or IMC used in that application would require one.
Regards,
- Kenneth
The first house I rewired, I noticed that the electician had done it the way I describe above. I wondered if it was against code, because I followed those diagrams exactly, as you did (those code books are similar between provinces). Then the second house I rewired, I noticed that the electician had done it as above as well. This is common practice when there are only two Romex wires going into the box, and it evidently meets Canadian code. I searched the Alberta code book for an explanation, and found a sentence that describes and approves the above pattern.
Remember that for this configuration, all ground wires first go to the box. If there are more than two then you definitely do need a pigtail, because there aren't enough ground screws in the back. No more than one wire per screw is a critical point.
It seems redundant if you are using a pigtail, 'suspenders and a belt'. But you won't get a complaint about that at inspection, and I suspect it may be marginally safer. I have always had a habit of doing it that way in the interest of safety. By the way, I like the long 8" wires you are using. For sure, don't use anything less than 6".
Go around at least 270, use needle nose pliers to pinch it around the screw, then screw the nut tight.
First a general comment: If a box will contain a device (outlet or light switch), in particular a big device like a GFCI or a locking or dryer outlet, I would use a bigger and deeper box. My favorite is the
4x4 >If you don't have many to do, you might look for some ready-madeHighly recommended. They are a red wire nut, with a green, white or black pigtail (stranded flexible 12-gauge), and a real spade connector. You can take all the solid wires, neatly make them up (connect them together), and arrange them tightly in the back of the box. Then the pigtails for the outlet (or switch) stick out neatly into the middle of the box. The whole works looks pretty, and impresses the inspector. After he's done with rough inspection, it is super-easy to connect the outlet after drywalling, without having to mess around in the big spaghetti nest in the back. Unfortunately, they are not dirt cheap (a few $ for a bag of 10). Clearly, the inspector will know that this job was done by an amateur (I bet professionals are too cheap to use them, and experienced enough that they can do a neat job even without them), but the inspector will know that anyhow.
I think what you're describing is: One ground goes to one grounding screw on the metal box. Another ground goes to another screw on the same box. I'm not sure that this is legal. Here's why: The NEC says that grounding (or neutral for that mater) must not be interrupted if you remove a device. So it is illegal to use the two neutral screws on an outlet as a "distribution point" of sorts. Now, the box is not a device, and would not be removed, but I worry that using the sheet metal and two gronding screws might be pushing it.
The following, however, is OK: Take the incoming ground and leave it really long (maybe 15"), wrap it all the way around the ground screw, and tighten it. Now use one of those special wire nuts with a hole through the middle (I've heard they are called "greenies"), and use it to connect the other ground wires to this ground wire. You still have a few inches of pigtail sticking out of the wire nut, which you can now use to connect to the outlet. I think this is OK (one of the professionals might disagree, or bless it), and the most efficient way to handle the ground.
I th> In your conductor allowance, you made two allowances for clamps for
No, one allowance per INTERNAL clamp. One clamp can handle one or two cables. The internal clamps can usually two. The external metal ones (two screws, put into a round 1/2" knockout) can actually handle two
12-2 or 14-2 cables, but that seems so hokey to me, I try to always run only one.The plastic ones that go into knockouts are always labelled on the box or bag as to what combinations of cable they can handle. I don't like using those at all, because they don't seem to grip the cable tightly, and if you check whether they are tight and yank on the cable, you can actually damage the white jacket on the Romex. So I only use them if space is so tight that I can't tighten the screws on metal clamps. Do they need an allowance? Beats me. Technically, they are outside (you push them into the knockout from outside). But they are not really outside the box (most of them sticks inside), so I give them one, just in case. I don't even want to know whether the clamps on plastic boxes require an allowance or not. First, I don't like plastic boxes much, they are not sturdy enough for outlets in my box (they are suitable for light switches and smoke detectors, at best). And second I won't use them where the fill is even close enough that the clamps matter; they are too hard to stuff.
The metal clamps always go outside (the screws are outside), and don't need an allowance. They are actually the only clamps I really like. They look sturdy, and hold the cable well.
Don't know whether it is required. But they actually make clamps for this purpose. They clamp onto the EMT with a setscrew, and then have a cable clamp (like the clamps described above) for the NM. I just installed one; they're available at either Home Despot or Lowe's. Makes it look very pretty.
For deburring the EMT: There is a tool plumbers use for deburring. About the size of a tennis ball, it is an external and internal reamer. Very convenient. While we are on this topic: From painful experience, don't use a plumbers pipe cutter (the ones with a rotating round blade) on conduit! They really neck down the cut, and leave a very sharp burr on the inside of the conduit. If you use one of these, you'll have to spend 5 minutes reaming and filing the conduit. It is much easier to use a hacksaw, and then quickly debur the cut with a few strokes with a file or a reamer. When taking out the old wiring I did 8 years ago, I found one EMT that I had obviously cut with a pipe cutter and forgotten to ream. The wires inside the conduit had shredded insulation and copper showing. I'm amazed I didn't get a short or ground fault at that point. Scary.
WARNING: I've not had my current job inspected yet, so my advice might be all nonsense. I'll let you know what the insepctor says ... if I still have electricy at my house after he red-tags me :-)
| Running a cable into and out of a box with a receptacle in it has got to be | a fairly routine thing -- practically unavoidable. You don't mean they require | 3.5 deep boxes in the States? (If so, they must be easier to stuff!)
The last time they tweaked the numbers I remember commenting to someone that the most common single-device configuration (cable "in", device, cable "out") now requires the deepest commonly available gang box. With #14 2+G cables that leaves one conductor allowance, I think. So you can make one or the other (but not both) cables 3+G. Anything more complicated and you have to go to multiple gang boxes or a square box plus mud ring. I never buy anything but the deepest boxes unless I have a special (particularly cramped) application.
Dan Lanciani ddl@danlan.*com
I'm pretty sure you could use the hot screws/terminals on the device as a distribution point. If you destroy the continuity of the hot conductor be removing the device, it's not a safety issue. So connect the incoming black wire to 1 hot screw and the outgoing black wire to the other hot screw and you've eliminated a wirenut and a pigtail. You just can't do the same with the neutral nor the EGC.
Good luck with that.
Bes regards, Bob
With respect to the neutral, Section 300.13(B) of the 2002 NEC says continuity must be maintained with the removal of a device, but it only applies to multi-wire branch circuits, i.e. 240V/120V circuits. Is there something in the NEC that would require this for 120V-only circuits? I've wired all my (backwire screwclamp) receptacles with out pigtails on the neutral.
Cheers, Wayne
I did the same thing and the inspector passed it, and I was wondering if I should redo the neutrals.
In one box, I had 3 wires on each side of the backwire screwclamp devices (they had enuf back terminals for 8 wires) and the inspector said I had too many wires on one device and he made me change it.
Bob
According to James Owens :
Not quite. While the code book may not make this clear, the 1.25 inch allowance is primarily for stud/joist/plate crossings. Because it's along the studs, joists and plates where you're going to fasten the wall covering, and where the fasteners will penetrate.
So, the wire sticking out of the bottom or top of a box isn't at risk from being hit with a drywall screw (unless the drywaller misses).
Yes, you could worry about screws for shelves and such not anchored in studs, but you're not likely to install one of those that close to a box.
Certainly, an inspector is going to prefer you stay away from the wall surface, but they won't in this case.
In my garage, the inspector said I could install the wires on the bottom of the roof trusses (because the ceiling was already insulated and vapor barriered), as long as I made sure I had 1.5" of clearance whenever the wire crossed ceiling lathe (where I'd fasten drywall). Virtually in contact with the drywall at other places - I wouldn't screw to the trusses, because there was a 3/4" gap from the lathe.
According to Dave :
Interestingly enough, I read the Knight book somewhat differently (at least an older one).
The Knight book doesn't seem to trust the connectivity between ganged boxes that much.
So this is how I do my grounds:
- The feed ground is left very long.
- connects to a screw in each ganged section.
- thence to each ground terminal on the devices in the box (almost never more than one. The switches I use don't have ground screws on metal boxes)
- the final end wirenuts to the rest of the ground wires (feed thru).
When pushed to the back of the box, takes up almost no room, no pigtails required.
With hot wires, I "slide" the insulation for each screw, and can attach to multiple switches that way, only needing a wirenut if there's a feedthru unswitched hot. Only rarely use the second screw of an outlet for feedthru.
For neutrals in a standard single outlet feed thru situation, I slide the insulation to connect to the outlet, and wirenut the end to the feedthru wire. On multi-wire (split-duplex) too.
I've had inspectors inspect lots of wiring done that way, never any trouble.
Almost never need to use pigtails.
For sure, multigang boxes need direct connection. I don't like those multigang boxes, screwed together with a flimsy screw. They seem rickety compared to a welded box. The box he describes is a single gang box, not multigang.
This seems fine.
This sounds like an interesting idea, and I think it would allow the necessary ability to remove a fixture without disrupting distal connections. I'm not so sure it is easier to do compared to pigtails, and you don't save any wirenuts. With this plan if you remove a fixture and turn the breaker back on, you need to tape the bare section of wire to prevent fire (wirenut won't easily fit on a bare segment of wire with no end.)
Between studs, the wire will be pushed away from a drywall screw because it is not firmly attached at that point. Loosly attached, the wire deflects away rather than being pinned against a wire staple, or in a hole for a stud. However I read the 1.25" guideline as anywhere, whatever angle, including the rear of electical boxes, to the surface of the stud and the outer edge of immobilized wire. If a drywaller hits something with a 1 1/2" screw, he can protest that the other tradesman is the one at fault. Better safe practice for confidence later, I would use the metal plate behind those extra deep boxes. However if the circuit is planned carefully, you don't often need the extra-deep boxes.
Dave
"Chris Lewis" wrote in message news: snipped-for-privacy@uni-berlin.de...
:I've tried folding the wires accordion-style in advance of ;connecting the outlet and that helps a little, but I still feel like I'm :cramming the stuff in.
I don't like accordion folding because it flexes the wires at a few points and at sharp angles. I "cork-screw" the device into the box instead. The wires are bent continuously over the whole length, and tends to make it easier to push the device into the box.
Chris Lewis posted for all of us....
Hey Chris could you post some pix? I am imaginably challenged (stupid)
According to Dave :
True enough. But I don't think I've ever wanted to power up a circuit once a device is removed in this fashion.
I usually don't do that trick with the hot on a simple passthru connection for an outlet either.
But it makes a huge difference with workability on wiring ganged switches.
I usually arrange each fixture's feed to the top of the ganged box, arriving in the box where its corresponding switch is going to go. The power feed comes in the bottom at one end of the gang. [I almost always have the unswitched power going to the switch box, rather than using switch loops.]
Route the feed grounds under one box screw per gang, then wirenut to the fixture feed grounds. Push back flat against the back of the box.
[If you have multiple devices requiring grounds, you can route the ground just like the black below.]Wirenut all the neutrals together as usual and lay in.
Then, strip the black feed in multiple places, and string the switch bottom screws to it. If I have a hot feedthrough to elsewhere, wirenut that. So now I have the hot wire hanging out with all of the switches strung on it. Attach the corresponding fixture blacks to the other screws, and bolt the switches in.
Once finished, it's surprising how _little_ room in the box is taken up by wire. And identifying which wire/cable is which is trivial - easy to rework things later.
I wish I could show pictures, but I don't have good samples around here that are accessible. I'd have to fake it. Then find somewhere to post it.
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