Connecting only one wire per device in a box.

Does the NEC say that you can only connect one set of wires per device in a box? The reason I ask is because I was working with an electrician and he
had me pigtail every connection where we fed multiple outlets with one feed. Here's what I don't understand about that. If I am running a feed to a pigtail which is made using either wire nuts, or those push in three hole connectors, how is that a more "failsafe" connection than using the screws on the sides (top and bottom) of the outlet? I have seen times where a wirenut has fallen off of a connection (I assume from vibrations caused from walking or jumping around) and the push in connectors, although very quick to use, seem to work similar to the push in feature in the back of outlets which I was told from a teacher never to use because they only make contact with a small area of the conductor and that isn't as solid of a connection. Would someone clarify this for for me? I wired my house using the top and bottom of the outlet and just pigtailing the ground, but now I am thinking I might have to go through and add pigtails to the hot and neutral too.
Thanks
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gore wrote:

If you are installing UL listed receptacles or switches and they have push in terminals then they are permitted if used according to UL instructions. You can push one wire in one hole for supply and push another out going load wire into the other hole and not use a wire nut at all if you are not using a multiwire branch circuit. Multiwire branch circuits require pig tailing. Your teacher may have told you to do a better quality and reliable job by using wire nuts and the screws. However, as an experienced state inspector that rejected the use of the push in terminals on a school job because I thought like your teacher, but who got egg all over my face because the contractor went over my head and had my report nullified. If the UL listing says it's ok, then it is ok, and the contractor wants to make money. The push in terminals are much more efficient.
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From my understanding: A typical garden-variety duplex receptical is generally rated for 15A, while your branch receptical circuit is normally over-current protected at 20A. If you wire to the screws or push-in terminals, you potentially limit your current carrying capacity to 15A total for the remainder of the circuit (including the load on the first receptical) and the first receptical in the string could potentially become the "fuse" for the circuit. I have _always_ pig-tailed receptical circuits. It takes a bit more time, but the peace of mind is worth it imho.
--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
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| A typical garden-variety duplex receptical is generally rated for 15A,
Even if the configuration of the holes in front designate it to accept only a "15A style plug", these are supposed to be rated at 20A total for a UL listing. Perhaps the actual contacts in half of a duplex may not handle more than 15A, but the whole thing has to handle 20A.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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Not true. 15A receptacles will carry 20A just fine. They are the same receptacle except for the slot configuration on the front.
Ben Miller
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Benjamin D. Miller, PE
B. MILLER ENGINEERING
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gore wrote:

With pigtailing throughout, you can pull a receptacle without disturbing the rest of the circuit. It's a higher quality job. If you did not pigtail, but did things right at the time you did the installatiom, you have nothing to worry about.
Don't use those )*&%$! backstabs. They may be solid when initially installed, but over time the metal contacts lose tension and the once reliable connection becomes a problem.
Regarding wirenuts - in a properly done wirenut connection, the wirenut will not fall off.
Ed
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| Regarding wirenuts - in a properly done wirenut connection, | the wirenut will not fall off.
Maybe it's because they were not done properly. But every failed connection I've ever encountered has been a wirenut splice or pigtail that, while staying together, ended up overheating due to a poor electrical connection. I've never encountered such a failure for screw on terminals at the devices. Personally, I would prefer that the circuit go _through_ the device rather than around it where a pigtail is required. For a basic 2-wire circuit, that's easy to do. For a shared neutral it's not unless the device can be wired across both poles of the circuit and has the 6 screws needed for in and out on all 3 wires of a 3-wire shared neutral circuit. OTOH, I intend to have no shared neutral circuits supplying multiple devices.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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Thanks for the responses. I did use the top and bottom screws when I wired my house, but I can see the advantage to pigtailing now. If for some reason I might have to change an outlet it would be faster to loosen and hook up 3 connections than 5 the way I have it now. Anthony made me think a little about the 15 amp fuse thing though which makes me want to ask another question. I read one of the posts either in this group or in alt.home.repair that the breakers were to protect the wire more so than the device connected to the wire. If this is the case is the metal connecting the 2 screws of a 15 amp outlet actually designed to open if a load greater than 15 amps is drawn? Not trying to be an idiot here, but I took only a 10 week course in electricity and am finding that there is a lot more to learn. The pigtailing thin only came up in the course after we had used all of the screws on an outlet and need to feed more devices on the circuit.
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gore wrote:

The facts are it is up to the electrical specifications whether or not you pigtail. If the estimator put in the time you can pigtail, but if he didn't and you pigtail, and refuse to follow instructions you will be sent down the road. I have seen many electricians sent packing for trying to do what they think is right and going over the bid price. Some electricians are so conscientious that will quit before doing a job they think is not a quality job. I have seen it happen many times. However, these types of electricians are great on cost plus jobs like the original Trans Alaska pipeline. But for home jobs, you can do it as you see fit. However, pigtailing will require larger boxes to meet code. Remember, 2 cubic inches are required for each No. 14 AWG and 2.25 cubic inches is required for each No. 12 AWG. Counting these the number of wires can be difficult but here are the rules:
2005 NEC 314.16(B) (B) Box Fill Calculations. The volumes in paragraphs 314.16(B)(1) through (B)(5), as applicable, shall be added together. No allowance shall be required for small fittings such as locknuts and bushings. (1) Conductor Fill. Each conductor that originates outside the box and terminates or is spliced within the box shall be counted once, and each conductor that passes through the box without splice or termination shall be counted once. A looped, unbroken conductor not less than twice the minimum length required for free conductors in 300.14 shall be counted twice. The conductor fill shall be calculated using Table 314.16(B). A conductor, no part of which leaves the box, shall not be counted. Exception: An equipment grounding conductor or conductors or not over four fixture wires smaller than 14 AWG, or both, shall be permitted to be omitted from the calculations where they enter a box from a domed luminaire (fixture) or similar canopy and terminate within that box. (2) Clamp Fill. Where one or more internal cable clamps, whether factory or field supplied, are present in the box, a single volume allowance in accordance with Table 314.16(B) shall be made based on the largest conductor present in the box. No allowance shall be required for a cable connector with its clamping mechanism outside the box.
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snipped-for-privacy@electrician2.com wrote:

Here are the rest of the rules: (3) Support Fittings Fill. Where one or more luminaire (fixture) studs or hickeys are present in the box, a single volume allowance in accordance with Table 314.16(B) shall be made for each type of fitting based on the largest conductor present in the box. (4) Device or Equipment Fill. For each yoke or strap containing one or more devices or equipment, a double volume allowance in accordance with Table 314.16(B) shall be made for each yoke or strap based on the largest conductor connected to a device(s) or equipment supported by that yoke or strap. (5) Equipment Grounding Conductor Fill. Where one or more equipment grounding conductors or equipment bonding jumpers enter a box, a single volume allowance in accordance with Table 314.16(B) shall be made based on the largest equipment grounding conductor or equipment bonding jumper present in the box. Where an additional set of equipment grounding conductors, as permitted by 250.146(D), is present in the box, an additional volume allowance shall be made based on the largest equipment grounding conductor in the additional set.
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snipped-for-privacy@electrician2.com wrote:

Please explain how, when pigtailing, the US-NEC requires a larger box.
I agree with ehsjr on backstabs. I have seen a lot of other posts not to use them and no posts recommending their use.
I also agree with ehsjr that properly applied wirenuts are very reliable and won't fall off.
A 15A duplex receptacle is rated for 20A pass through (screw-to-screw) and 20A total current from the 2 receptacles.
With some exceptions, like motors, circuit breakers protect the wire and the equipment connected. Equipment sometimes has an internal line fuse, but more often not.
On multiwire circuits (hots from both legs and a neutral) the neutral is required to be pigtailed. That prevents the neutral from being disconnected for the downstream circuit (a real bad idea) if the receptacle is replaced with the circuits hot.
-- bud--
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Bud-- wrote:

You got me bud, I made an error. It is not a code issue, but sometimes the additional wire and wire nuts can make it difficult to stuff the box.
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Well, about a year ago I picked up some wirenuts with a built in flexible wire pigtail.
I used a few of them. The advantage is that you pack in the solid wire and the wirenuts and you have the flexible wires to connect to the outlet. If you wire through the outlet you end up stuffing an outlet back into the box with 5 solid wires attached.

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John Gilmer wrote:

Somebody needs to develop a hydraulic press to get these devices into boxes.
;-)
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Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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Well, "they" make a gadget that plugs into a duplex outlet that helps guide it into place.

It's on the list of things I always wish I had but never buy before the need.
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| Thanks for the responses. I did use the top and bottom screws when I wired | my house, but I can see the advantage to pigtailing now. If for some reason | I might have to change an outlet it would be faster to loosen and hook up 3 | connections than 5 the way I have it now. Anthony made me think a little | about the 15 amp fuse thing though which makes me want to ask another | question. I read one of the posts either in this group or in alt.home.repair | that the breakers were to protect the wire more so than the device connected | to the wire. If this is the case is the metal connecting the 2 screws of a | 15 amp outlet actually designed to open if a load greater than 15 amps is | drawn? Not trying to be an idiot here, but I took only a 10 week course in | electricity and am finding that there is a lot more to learn. The | pigtailing thin only came up in the course after we had used all of the | screws on an outlet and need to feed more devices on the circuit.
What looks like a 15A device is really a 20A capacity device, with only the possible exception of 15A maximum per individual outlet (half of a duplex). To get the rating it must handle 20A total in any combination of usage by either of the 2 outlets or the next downstream connection(s). In many cases the internal conductor construction of what is a NEMA 5-15R device is the same as a NEMA 5-20R device but with the openings cut different in the face.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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If the receptacle is listed and designed for two wires, then it is perfectly acceptable to install them. This applies to multiple rear entry or side entry holes, or screws that have a clamping plate. You can not install two wires into a single hole, or wrap two wires around the screw itself.
Ben Miller
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Benjamin D. Miller, PE
B. MILLER ENGINEERING
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Thankyou all for your help.
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