Wiring a Junction Box: 1 source in, 2 sources out

I have an existing junction box and currently 1 source from the basement going in, and one source coming out and that goes to a wall switch.

If I want to connect a second wire to come from that junction box, would I just attach all hot and all neutral wires together in the box? In my head it sounds like this wouldn't be a complete loop, but maybe I am just overthinking it.

So one source going into the box and then two wires coming out of it, each going to their own box in the walls below.

Anyone have a diagram for this? Thank you!

• When you say "wire" in the first context, you mean "cable"... For instance NM cable has 2-4 wires in it plus a bare ground wire. It's a lot easier to understand that way. Jan 30, 2016 at 2:12

Yes, you would tie the hots together, the neutrals together, and the grounds together. Below is an image of the inside of the box for reference.

And here is a wiring diagram as requested. The main line from your breaker comes in at the top of the diagram and enters the box. It is then tied off and sent to the left to your always hot load or other switch and also to the right towards the existing switch and load. (Black is hot, gray is neutral, orange blobs are wire nuts, and grounds are not shown for simplicity)

I've also included a more clear cut version of the diagram so that you can see the flow of power.

• Okay thank you, that was an image I was looking at earlier. I just wanted to make sure that if the two wires (connected together with the source) going to the seperate gang boxes, wouldnt cause issues. In this case they are just sharing power correct? I look forward to your image. Jan 29, 2016 at 19:25
• And the wires going to the top part of the image can have the same type of loop? Adding in a switch and bulb? Jan 29, 2016 at 19:29
• Yes, that's correct, they are sharing power. They are in 'parallel' with each other where the power is divided between the two.
– TFK
Jan 29, 2016 at 19:30
• And yes. The top wires on my diagram are where the power is being brought in from the breaker and so keeping with it, the left side would go to the new loop, but yes you can branch off and create it's own loop.
– TFK
Jan 29, 2016 at 19:31
• In the top picture, why isn't ground coming from the breaker box? Also, if you are connecting grounding cable (bare copper / green) to breaker box, is it still necessary to hook it to junction box? What is the JB is plastic and not metal? Jun 12, 2019 at 21:09