I can't find a question like this, but I might not be using the right terms. I am in the US. I need to add a double outlet to an existing circuit. I have all the wires in place, but I don't know how to wire it up. Below is my diagram of what I want

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The diagram also shows the plugs positions to each other. I can't run a wire from the new outlet, to the far right one. I have the new wire in the wall, with a new double outlet box in place.

There are two different Romex wire bundles into the first outlet. The outlet has both sides of screws wired. enter image description here

The grounds are bare copper wires.

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How can I wire in the double outlet off the single outlet in the wall?

  • In the US, most receptacles are "dual receptacles" - you can get singles but they are generally only used when there is a specific reason. So what do you mean by "single" and "double" - are they literally places only 1 or 2 devices can be plugged in? Or are they actually "one thing = 2 receptacles" and "2 things = 4 receptacles"? – manassehkatz-Moving 2 Codidact Dec 8 '19 at 18:47
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    Where are you located? Codes and habits vary from place to place. – Aloysius Defenestrate Dec 8 '19 at 19:25
  • Can you post photos of the inside of the box you are wanting to tap from? – ThreePhaseEel Dec 8 '19 at 19:57

Since you don't give many specifics I'm going to make a few assumptions: You are in the US and single means one device with two plug-ins and double means two devices with a total of four plug-ins. I'm also assuming that the two wires in the box you are sourcing your power from are black and white with a third bare copper ground. First - make sure to shut down all power at the breaker box. You can then either connect to the unused screws on the powered receptacle attaching black to the same side of the receptacle as the black (hot) and white (neutral) to the other side or you can pigtail the blacks together, the whites together and the bare copper grounds together. If you pigtail you will then have three wires in each pigtail. One for the line coming in, one going to the single outlet and one going to the new double outlet. At the new double outlet you will need to again pigtail black to black, white to white, ground to ground with three wires on each pigtail - one for the line coming in and one for each outlet. Run the two blacks (hot) to the hot side of each outlet - it will be marked. The two whites (neutral) to the other side and the grounds to the ground screws. Now the most important part. It's nice to add on outlets for convenience but you don't want to overload the circuit. You seem to have a number of outlets here that are running on what appears to be one circuit. It's critical to know what size circuit you are working with (15 or 20 amp) and what is on that circuit. This means not only outlets and lights but more importantly what is plugged into those outlets. You have to consider watts. A 15 amp circuit delivering 120 volts is only rated to handle about 1440 watts (15 x 120 x .8) 20 amp is about 1920. For example a hair dryer pulls between 1300 and 1500 watts. Appliances will indicate how many watts they draw or you can find out online. If you overload the circuit you'll be constantly tripping the breaker and posing a safety risk. Good luck but be careful and think it through.

  • Thank you. I have added a bit more specifics and pictures to the question. There are two romex wires in the outlet box I want to split from. One comes in, and one leaves the box and goes to the other outlet on the circuit. – Siriss Dec 8 '19 at 20:17
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    Also note that box may not be large enough, if the wire is all #12 the minimum cubic inch size you must have is 20.25 cu. in. (6 circuit conductors + 1 ground + 2 for device = 9, times 2.25 c.i. per wire = 20.25). – NoSparksPlease Dec 8 '19 at 21:23

I get it. You see 2 screws on the side of the outlet, and figure, "only 2 wires are allowed - no branches". No, thats only a limitation of the splice method, like a 2-hole Wago. If you had a 6-hole Wago you could connect 6 wires to that splice.

In particular, you are using the receptacle itself as a splice. That is a clever way of saving some space in a box. But you're not married to it. Feel free to use any legal splice method.

You can pigtail off the receptacle and then use Wire nuts, Wagos, lever connectors, Alumiconns, Euro splice blocks, split bolts, screw-to-clamp receptacles... Whatever floats your boat. As long as it's UL listed and the instructions say it's for splicing.

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