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I'm going through my new home and replacing my outlets. This was mostly fine, as the first outlet was very easy to replace. But, I ran into outlets that have multiple hot/neutral wires.

For the most part, I just copied how the old outlets were setup by plugging in the wires into the holes in the back and the "extra" ones screwing onto the side screws, and this worked fine (I hope). The problem I ran into is I wanted to replace some of my outlets with the newer USB/Outlet combinations, which only have one set of screws (and one pinhole in the back). Basically, I don't know what to do here; I don't think it's smart to put multiple hot/neutral on the same screw.

USB Outlet

A few questions:

  1. Why on earth are there multiple hot/neutral wires for one outlet?
  2. What do I do for the USB outlet which does not seem to have enough screws to handle 3 hot/3 neutral/1 ground?
  3. Can I do anything to deal with all these extra wires? They make it harder to screw in the outlet because it is so crammed in there.
  • Could you add a picture of one of the old outlets? – Grebu Dec 31 '16 at 15:37
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    Please do not follow @TomCarpender 's advice. He gave an answer for the United Kingdom which is not applicable to the USA. – DoxyLover Dec 31 '16 at 19:19
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    By the way, that photo is insanely wrong. First, the drawing diagram shows hot and neutral on the same side, not impossible but I've never seen it done. Second, screws are properly brass for hot and silver for neutral. This photo shows both brass (reasonable) on the neutral side (very very wrong). Third it claims the screws are the same color yet different poles. The photo is a trick of the light, the legend must be wrong. Or it's a severe case of China Syndrome. – Harper - Reinstate Monica Sep 20 '17 at 16:00
  • A few observations: The illustration is WRONG, and we're looking at the two neutral screws here (not one). I agree that these screws "look" gold, however I am confident this is an artifact of the color balance of the photo (remember when the Internet exploded over "is the dress gold or is it black?" << THIS). Without a pause I would place a monetary bet that left side (when ground is down) is always Neutral per NEC, for one reason being there is always a tab "joining" both screws (you can break it off for circuit independence). Allowing random polarity placement would kill the color blind. – Scott Prive Feb 18 '19 at 0:55
  • @Crossfit_and_Beer: The photo is directly from the manufacture of the outlet. The outlet does indeed have a brass, silver, and green screw as identified in the photo, even if the photo colors are not really identifiable. – m-y Feb 20 '19 at 14:58
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  1. There are multiple wires because that is how wires are connected to gather to get from the distribution box to the farthest outlet on the circuit.

  2. Where there are not enough screws, you attach the outlets together with a connector with an additional short "pigtail" that goes to the device.

  3. If there is not enough space, you change the box to a deeper one or a wider one. Where you are installing a larger device, that may be required by code. Code has formulas and tables that specify minimum box size. It is a bit difficult to follow and I don't recall how it applies when a different type of device is installed. I think different types of devices are assigned "fill factors" that may be marked on them. The box size may also be marked on it and be readable by looking inside closely with a good light.

Your photo appears to be a USA type device. If you are in the USA , the applicable code is based on the USA National Electrical Code (NEC). There may be local exceptions and additions, but there are usually not many. That and the NEC guide book are often available in public libraries. I believe putting two wires on one screw as suggested by @Tom_Carpenter is not allowed by NEC. Also NEC required any connection to be inside junction boxes that can be opened for inspection. Nothing like that is allowed to be hidden inside a wall.

State and local codes specify who is allowed to install or modify wiring, what permits are required for each job etc. You can get away without following codes, but you could run into trouble when you go to sell your house.

Also, ring wiring as shown by @Tom_Carpenter is not done in the USA.

The Leviton site makes it clear that the side screws are designed for a wire to be looped around in the shape of a shephards's hook. NEC requires terminals that are designed for more than one wire to be so marked. Those types of terminals generally have a groove for each wire or some other mechanism to hold two wires securely. NEC requires all devices to be used and installed in the way they are designed to be used and installed.

  • +1 Note that you can join the pigtail with a wire nut, however it might be a bit tight in the box with wire nuts and the relatively large USB receptacle. Here are relevant instructions from Leviton. If you need more than 2 wires (one side + one back) you need the pigtail option. – Spehro Pefhany Dec 31 '16 at 19:35
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Extra wires go to downstream sockets or loads

Circuits are usually in strings of junction boxes, daisy chained. They can fork, too, and in that case you'll have 3-4 cables needing to be spliced.

Shoddy workmanship

If you're finding places where the backstabs AND the screws were used, you're looking at shoddy workmanship. Generally you're only allowed to use backstabs OR screws. That only allows 2 connections on a common socket. (4 on the better ones).

In any case, if you have more wires than screws, use a pigtail. Put a 6" section of wire on hot and neutral on the socket, then wire-nut it to the other relevant wires. (but the illustration shows orange wire-nut, but yellow or red would be better.)

enter image description here source

In fact, many electricians dislike backstabs. They don't grab well. They're single-use: prying out the wire and reusing the hole makes them weaker. Heavy loading heats them, which weakens the spring. They're not even legal for grounds. What do you expect with 4 backstabs in a 60-cent socket?

Use side screws, or up-spend on the $4-tier "screw-and-clamp" sockets. Those allow up to 2 wires per screw, or 4 wires per side.

UK is unique

Above (below?), Tom describes ring circuits which are a UK idiom. Don't hook up branch circuits like that anywhere else, least of all North America!

  • Hey I'm no fan of backstabs, but you seem to be suggesting that "mixing" screws and backstabs is against code. Are you in fact saying this, and any chance you have a reference so I could take a look? Now I always take time to make a pigtail, but if it was against code to use screws-with-backstabs then I will go redo some of the first outlets I set up. – Scott Prive Feb 18 '19 at 1:05
  • @Crossfit_and_Beer my understanding is that it is, but I don't have a code cite handy. Regardless, 110.3b certainly applies: you must follow the device's labeling and instructions. As a practical thing, "using screw and backstabs is bad" is a subset of "using backstabs is bad". – Harper - Reinstate Monica Feb 18 '19 at 1:09
  • Thanks. I did a little more searching and found the NEC is apparently silent on the issue, "however" UL expressly prohibits it -- which makes it fall under more general NEC prohibition re: usage. forums.mikeholt.com/showthread.php?t=92147 – Scott Prive Feb 18 '19 at 13:59
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The reason for multiple hot/neutral wires for one outlet is that the outlets are daisy-chained together. This means hot/neutral is only coming from one of the wires and it is being sent to the other wire. This saves on the amount of wire needed since nearby outlets can be daisy-chained instead of requiring wires from the circuit breaker to each outlet.

Take a look at the general schematic for wiring outlets below. You can see that each outlet is wired in parallel like I said. In addition, the point where the first and second outlet connect, that is where you would screw both hot/neutral wires to the screw.

schematic

simulate this circuit – Schematic created using CircuitLab

Only one wire actually contains the hot/neutral power (the one coming from the circuit breaker), while the other one is meant to pass along the power to the next outlet.

For your second question, I would recommend you try putting both hot/neutral wires on the screw terminal if you can. I have had to do something similar when there are many hot/neutral wires to worry about.

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Install pigtails if there is more than one cable in the box. Using a scrap of the same type of circuit cable, cut 6-inch lengths of each type of wire in the cable and strip 3/4 inch of insulation from each end of the wire.

Join the bare copper (or green insulated) ground wire to the ground wires in the circuit cables using a wire connector, following the manufacturer's directions. Do the same with the white (neutral) wires, then the black (hot) wires, so you have one ground, one white, and one black pigtail.

Note: If the electrical box is metal, install an additional grounding pigtail and connect it to the ground screw on the box, as described in the next step. The outlet will have its own separate grounding pigtail.

How to Wire and Install an Outlet

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