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I'm replacing the outlets in our house and pulled out one that had two black and two white cables. My first thought was that it was two circuits, one of them being switched, but then realized the tab between the two circuits wasn't broken.

I hadn't seen this before, but I guess it makes sense. I suppose it's an alternative to pig tailing the wires in the box. Is there an argument to choose one method over the other? Or are they both perfectly valid option?

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there are two sets of wires because one set is charge (coming into the outlet) and the other one is load (going out to the next box/outlet). nothing unusual about it. the tab is not broken because it serves to connect the two –  amphibient Apr 10 at 17:00
    
@amphibient oh, to clarify, I got why there were two sets--I just wasn't used to seeing the outlet, itself, being used to connect them. In past homes, that was always done via pigtailing. –  DA01 Apr 10 at 17:07

11 Answers 11

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I rarely see pigtails to join the outlet line/load connections in any of the renovation work I've done. I think it's just easier for the electrician to wire both parts of the outlet, rather than getting a small piece of wire, twist, affix nut, and attach to the outlet. It also takes up less space in the j-box.

Of course the line/load are pigtailed in other j-boxes (e.g. lighting fixtures and switches) since they don't have two screw terminals. And you would pigtail the lines before a GFCI if the next device shouldn't be protected by that GFCI outlet, but otherwise you would always use the line/load terminals in a GFCI.

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Well, I've only owned one home prior to this, so I suppose the person that did that one just preferred the pig tail option. –  DA01 Jul 9 '12 at 22:43
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Agreed, it's just easier when you're going around the room to wire up the 'north' and 'south' sides of outlets –  Aaron Jul 9 '12 at 22:44
    
The electrical inspector told me that pig tails are required. (So my receptacles all have pig tails) –  Craig Jul 9 '12 at 23:33
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@Craig Pigtailing is definitely the recommended practice, but I don't think it's required by code. –  Michael Jul 10 '12 at 1:43
    
Funny that your inspector wanted wire nuts over screws... in some countries (so I'm told), wire nuts are ILLEGAL - every wire must be under a screw. –  TDHofstetter Aug 20 at 18:21

It's easier to use the screw terminals (or stabbing them in the back, but that's not recommended practice as they will eventually fail) and an intact breakoff tab to chain receptacles together, but if one outlet goes out, all of the receptacles downstream will as well. This is the desired effect when you're talking about a GFCI outlet protecting the entire circuit, but if you're talking about a bedroom, etc. circuit that is not GFCI protected, there isn't much benefit that comes with the disablement of a part of or the entire string (other than it might alert you of the problem quicker.)

The majority of receptacles you'll see out in the wild are wired without pigtails. It's faster and the builders and contractors can't justify several extra hundreds of dollars (mostly labor, of course) just to do pigtails.

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good point re: one fails, they all fail. –  DA01 Jul 9 '12 at 23:25
    
Unless the failure is in the binding screws, the backing plate, or the break off tab, how does an outlet failure effect downstream receptacles? Current will pass thru this path regardless of what happens inside the recep. –  bcworkz Jul 10 '12 at 0:45
    
The binding screws could be one of the more likely failures as they carry the full current of the circuit and will heat/cool and expand and contract with use. A pigtail has a wire nut carrying the full circuit current and has "teeth" that bite into the copper which is probably more gas tight and resistant to heating. The PSI of a wire nut is much higher than a binding screw so the wire will deform and make an oxide free connection. –  Philip Ngai Jul 10 '12 at 1:05
    
@bcworkz Some types of failures will cause an outage for all downstream devices, others will not. It depends on the type of failure, but as Philip Ngai has pointed out, the screw terminal, backing plate, etc. is seeing more current, so it will increase the possibility of something going wrong. Stabbing the receptacles in the back is even worse, and it is very likely that you'll have a failure at some point down the road. –  Michael Jul 10 '12 at 1:49

Although the official rules don't take this into account, it seems to me that the box will have more "wire fill" with a pigtail. Although this is not a electrical or safety issue, it might affect how easy it is to put the outlet back in the box.

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I have never seen a pigtail of wires in a box with a receptacle. The outlet is always used to tie lines together. I think the advantage is reliability.

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We always use pigtails, it doesn't take long to cut/strip a few dozen 6" lengths of black and white 14/2 and fit them to all the outlets while working at a convenient height on a bench. You have to use a marette to join the incoming earth wires to a single one to the earth tab anyway, and 2 more marettes only cost a few cents. We also use boxes with enough volume to allow easy fitting of outlet and cables/marettes in it, it makes fitting the assembly so much easier, rather than cramming wire and outlet etc into a minimum (albeit code conforming) sized box. ;-)

The pigtails make life easier for me (as boss) too, the apprentice lays out the outlets with pigtails as they make them, I can see at a glance if live/neutral are right or reversed, so much easier than crawling along the floor inspecting each one. (I'm 60).. Finally on any job there will be 'down days' when the weather is @@@ or the inspector fails to show etc, just make up more outlets/pigtails for future use, you're paying the crew to sit around otherwise!

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In the UK, it is common to put up to 3 wires into the same screw terminal; I have never seen pigtails being used to avoid putting 2 wires into a screw terminal. Maybe the screw terminals we have are better able to cope with multiply wires in them.

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In California, it is code to pigtail wires. As an electrical contractor, I totally agree. If the outlet fails and it is not pigtailed... everything down stream from the outlet will also be affected and lose power. No pigtail sounds like the lazy man's idea on how to wire up something. However, I can not dismiss the argument that a pigtail takes up valuable space in a box and it can also cause problems in itself. I would be a proponent of box manufacturers being forced to make boxes bigger/deeper.

I laugh when I am at home depot and I see someone buying a lot of 2 x 4 handy boxes and some 14-2 romex. I know they are going to go wire up a room with illegal wires for outlets and jam them into this tiny box... because they will save some $20. And yes... they will not pigtail, because look... the outlet has two screws on each side. HEY, there is also a little connection between these two screws that could be cut to allow for dedicated switched outlet operation, or two different circuits... do not use it as continuation of the circuit to another outlet... use a pigtail and use 4" deep boxes with plaster rings for your installations... it gives you more space for the wires and the pigtails... and the cost - relative to having your house burn to the ground with jammed electrical wires - is really not very much more... REALLY! And use nothing but 12-2 for outlet circuits. 12-2 is good for 20 amps; 14-2 for 15. If you put 14-2 in and somehow connect it to a 20 amp breaker... failure means fire. 14-2 is for light circuits... but trust me, use 12-2 also... just in case you ever have to put an outlet on a light circuit.

I have been an electrical contractor in California since 1979. I really know what I am talking about, but of course, it is based on 34 years of working in the field and the laws of California (I am sure other states do not have the same restrictions). I have repaired a few items in homes that DID cause fires, caused by "smart" people who really knew they understood how electricity worked. I loved the three hour troubleshooting charge I had for one client, to figure out why a lot of outlets did not work in their house. I traced it to one of these little connection traces being burnt in half. The outlet where the problem was - worked ... but because they did not know how the house was wired, the rest didn't. It cost them $180.00 to find out that the homeowner himself had installed this outlet and figured that those two screws on each side meant exactly what many "experts" in this link have stated... it's easier to wire up the outlet that way.

So, go ahead and use both screws and no pigtails; I have bills to pay and could use your money to pay for your cheap idea of how to do something. Short cuts are NOT a good idea in wiring... they either cost you a lot in the future, or cause you to find another home after your home burns down. I am not leaving my business card here... I say this because I care, not because I want your business.

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Can you link to the code that requires pigtails (or quote the text here, or at least mention a reference number or something so folks can look it up)? –  Tester101 Apr 2 at 16:29
    
I agree with Tester. There is NO code requiring this, unless it is a local amendment. The comment that this is a good practice because an electrician has bills to pay is an over dramatic one. In all my years I have seen a good few receptacles with failed screw terminations. Even more with failed backstabs. That said, I am not getting rich or paying my mortgage by fixing them. –  Speedy Petey Apr 2 at 17:04

Though the NEC does not specifically state that you must use pigtails, it does say that you cannot rely on a device to provide continuity for a neutral. By using both terminals on an outlet, you are relying on the device to provide that continuity. The way around it is to simply use pigtails.

NEC 300.13 (B)

"Device Removal. In multiwire branch circuits,the continuity of a grounded conductor shall not depend on a device conections such as lampholders, receptacles, and so forth, where the removal of such devices would interrupt the continuity."

So there you go...use pigtails.

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How does this apply to GFCI protected outlets? –  mjcopple Apr 2 at 15:06
    
This only applies to multiwire branch circuits. –  Tester101 Apr 2 at 16:22

Mike quotes the code (300.13B Device Removal) but misunderstands what it means. The paragraph's 1st sentence starts out, "In multiwire branch circuits,". That means where 2 or 3 circuits with 1 shared neutral wire are passing through a box. You'll probably never see this kind of wiring in a home, but if you have 2 or 3 circuits sharing a neutral in the same cable or raceway supplying several fixtures and/or devices, they want you to pigtail the neutrals (and only the neutrals!) at each device or fixture connection.

Otherwise, because it violates common sense (and cost more in T&M), pigtailing is not recommended. One connection is always better than two, and a wirenut connection is no better than the dual screw connections on a duplex receptacle (never put 2 hooked wires under one screw though). The other part of that is, if you can't fold 4 or 5 wires each 6 or more inches long connected to a duplex receptacle neatly into a normal size wallcase, you probably shouldn't be doing this kind work.

The simplest explaination of the wiring method this code refers to is where you have two 3-wire cables terminating in a box - 1 feeding in and 1 feeding out to the next box. That's 2 blacks, 2 reds, 2 whites and 2 grounds in the box. The feeding black wire is one circuit on a circuit breaker, the feeding red wire is another circuit on a different circuit breaker and the feeding white wire is the shared neutral for both circuits. When installing a fixture or receptacle at that box on either the red or black circuit, they want you to pigtail the neutral wires to prevent interrupting the other circuit during removal (replacement) of the fixture or device.

Like I said, this is not a wiring method that you're likely to find in a home.

And in the case of a GFCI receptacle, you can't use the load side of a GFCI to protect a downstream circuit with a shared neutral anyway, so you still pigtail the neutrals to abide by the code. However, if there's a downstream circuit from that GFCI that's a 2 wire (1 circuit) offshoot, than since for that portion of the circuit's neutral it's no longer being shared, it isn't required to be part of the pigtailing and you can connect the offshoot to the load side of the GFCI. And that could be anything from a receptacle right next to the GFCI in a 2-gang config or several more fixtures and/or devices.

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I wan't able to find installation instructions from any of the major receptacle manufacturers. Though I was able to find this video from Leviton (a major manufacturer of electrical devices, in the United States). The video demonstrates how to install a receptacle (there's also a version on YouTube), and clearly shows the installer using both sets of terminals to make the connections.

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My personal experience. I plugged in a radiant heater into a 20A receptacle in my garage. It ran for about 3 hours before the breaker tripped. Also a burnt plastic melt smell. The entire garage was dead. I did a LFS (Look for stuff) and noticed the receptacle that the garage door was plugged into had a black soot color coming from under the receptacle cover. I had a very hard time removing the plug from the receptacle as it was melted into the socket. After removing the cover plate I noticed the receptacle was half melted. Remember the heater was not plugged into this ceiling receptacle. It was plugged into a GFCI on the wall. Further checking found the hot (black) wire insulation melted and was shorted to the ground (bare) wire. Replace wire & receptacle and all back to normal and heater ran good. Did notice screw loose connecting the black wire to receptacle when I removed it. To me this is the main reason for using pig tails on all recptacles. This is a new home built in 08' or 09'. We are 1st owners. Also the bedrooms have special GFCI breakers. They have all tripped at one time or another. I plan to redo all receptacle outlets with pigtails because of this possible fire I almost had.

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This was NOT due to simply using the screw terminals. It was due to poor connections. I have done thousands of receptacles using the screws and have never had a failure. They are clearly rated for the current of the whole circuit. I will also add, I have seen as many failed wire nut connections as I have receptacle termination failures. Also, the AFCI breaker tripping you are experiencing has absolutely nothing to do with the receptacle terminations either, unless of course they are actually arcing. Nuisance tripping is common with that vintage of earlier AFCI breakers. –  Speedy Petey Aug 20 at 23:00

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