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?
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.
I'm an electrical contractor in Northern California. Whether it's code or not, I ALWAYS use pigtails. The reason is simple: It's safer than using the receptacle for daisy-chaining to the next outlet.
In the East Bay, it's not uncommon to see 30 (to 75) year-old receptacles. I have personally seen three instances where the plastic hardened (especially the old bakelite), failed, and a continuous arc resulted between the internal hot and neutral contacts in the receptacle. In these cases, because the arc looked like an ordinary load to the fuse or circuit breaker and lasted for several minutes, the heat caused an electrical fire before the fuse or breaker finally tripped (or blew). (We have an old housing stock here, so AFCI (arc-fault) breakers/receptacles are not yet common.)
Since outlet pig tails and branch circuit feeders are held together with wire-nuts or push-in (e.g. Wago) connectors and the and neutral wires are more physically separate from each other, I regard the pig-tail method of feeding outlets to have a much larger margin of safety than using the receptacle for feeding the next downstream outlet.
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!
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.
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.
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 (in multiwire branch circuits). 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 device connections such as lampholders, receptacles, and so forth, where the removal of such devices would interrupt the continuity."
(emphasis ours)
So there you go...use pigtails.
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.
I'm not sure what the code says about pigtails vs. wire binding terminal screws to provide downstream continuity, but I always use pigtails to continue the circuit to downstream devices (plugs, switches, etc.). It does take more time but thats how I was taught. And by the way in the Canadian Electrical Code (CEC) pigtails are not counted in box fill calculations since they neither enter nor leave the device box, but each pair of marrettes used to make those pigtails DO count.
I don't know the rules in the U.S. Typically a receptacle feeding other downstream devices will contain three marrettes, one for each of the insulated conductors (blacks and whites) as well as a marrette for the bare bond wires. The rules say you only count PAIRS of marrettes when calculating box fill, so three marrettes means one pair, and will only count as ONE wire. And that's not much extra to deal with. Also, I prefer using the deepest boxes that will fit. This ensures lots of spare room as well as room for future expansion. Why struggle trying to jam it all in?
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.
I'm not an electrician. But I'm a nerd who has friends who've done forensic electrical engineering work. Here's a different perspective from above.
It's been code for like, ten years now, to use a torque screwdriver to tighten down the wire binding screws on outlets. Some of them take a surprising amount of torque! 18 in/lbs is way more than you think. This became code because Aronstein found countless failures and fires caused by poor threaded fastener binding connections. Many connections made by licensed electricians.
In other places, some have tested electricians in large numbers, and found something like 70% under tighten when done by hand, and 10% overtighten when done by hand.
Using a calibrated tool to apply the specified torque is the only way to ensure (1) the wire makes proper full contact initially, (2) that you make full contact without damaging the threads, and (3) that the connection stays correct for the next fifty years, and while under the extremes of it's uses. If it's under torqued, resistance will always be higher than it should be. If it's under torqued, the screw can definitely slowly loosen over time as thermal cycling from high loads causes the metals to expand and contract. If it's under torqued, you may also not fully penetrate the surface oxides.
If you back wire with pressure plate connections, you face all these problems, but worse, since friction is the only thing holding the wire in place.
If you use trash residential grade receptacles, all of the above problems are magnified greatly. If you use high end spec grade (or even "extra heavy duty hospital grade", as I prefer!), Then you have a tremendous factor.
Apparently, all this is why the code is moving towards pigtailing.
My advice to you, as a non-electrician to a non-electrician: if you're NOT using a torque screwdriver, aren't using high end receptacles, don't have AFCI breakers, and aren't testing the resistance of your outlets with a nice Ideal Circuit Analyzer, then pigtail with a high grade wire nut. You'll probably appreciate this at some point in the future. The ideal Mini Twists are nice for cramped boxes. 3m makes really nice fancy winged ones if you have space. As a non electrician, I find it hard to pretwist the wires without doing more harm than good! The instructions always just say "line em up and twist nut until wires themselves start to twist".
If you're an electrician, just please God go buy a goddamn torque screwdriver, and use it! They're now like forty bucks on Amazon! I've yet to see an electrician use one. It's code. It's also better for your customers. It takes like 3 seconds. I beg you. Do it right!
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.
In Australia and New Zealand, outlets are what Americans call "back wired". The holes have room for two or more wires to be looped through. Wires must be twisted together. In wall power wires can be stranded or solid, but the earth must be stranded. UK sockets are on "ring main", so every socket is expected to have wires feeding into and out of it from both directions.
To me, both methods have 2 connections that can fail. If properly done, they will most likely have the same probability of failing (with terminals being higher in earthquake prone areas).
I can see:
with both if the connection fails downstream outlets are affected.
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.
To pigtail or not... that is the question. As a Master/Electrical Contractor I avoid using pigtails when I can. I perfer to put wires under screws. I have never had a outlet failure in 30+ years of contracting that I installed. But I always use high quality material. I have seen wire nuts fail due to poor installation. They usually melt. I've seen them fall off wires. I have seen outlets get over heated by dumb people overloading outlets. I have replaced cheap outlets that failed with high quality outlets. Personal preference, no pigtails. In my opinion, it adds cost to a job, time, and introduces a potential failure point in a circuit.
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.
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.
Having been a certified electrician in california for 10 years, the first thing they teach you in a union apprenticeship is that pigtails save you on future call backs. The reasoning is this, most receptacles are only rated for 15AMP, and wirenuts are rated for at least 20 on yellows, or greys and probably 30 on reds. So your passthrough is the same as the wire itself. Receptacles are a weak point, meaning that they get torqued, and slammed and pulled. You don't want that to be your splice point. You want your splice on wirenuts, many times receptacles have razor blade stab in's which work well in a time pinch, but not when you are relying on them to carry 20 AMPs to the next 5 receptacles. If you do use receptacle screws, Don't use the stab in holes at least.
One method is the feed-through: uses the receptacle to carry on the circuit elsewhere and the receptacle must be designed to do so (note that not all receptacles allow feed-through), the other method is the pigtail one: wires are twisted inside a wire nut. They are both equally safe if done properly. Regarding the codes: that changes from country to country, for example in North America and UK the use of wirenuts (marrettes) is common but in other European countries marrettes aren't approved. Depending on the country one is in, electrical components are built and tested differently, rules and practices are different (my personal experience is with Canada and Italy for example). Obviously one follows the code that applies to them and inspectors will require whats fitting to the code according to them and their experience.
