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enter image description hereNeed advice on how to wire everything properly. There are two wire harnesses coming into the junction box:

  • H1: black(!), white, ground - comes from the fuse box
  • H2: black, white, ground, red(switch) - beginning of a circuit, extending into 2 rooms on the same floor.

I am adding an electrical outlet therefore i have black wire nut with 3 black cables, white wire nut with 3 white cables, red wire nut for the switch wire and ground cables are under the screws.

If I were to add a light fixture, obviously black is going under the same wire nut with red(H2), ground goes under a screw but I am not sure where the white one goes. From my understanding, it can go under the same white wire nut that will result in 4 wires on a same wire nut BUT i could be wrong. Still reading material but not able to put everything together when it comes to the neutral wiring.

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    hopefully the grounds ( green) are not actually disconnected like you show! – agentp Jan 26 '18 at 15:29
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There is a new rule that requires receptacles in bathrooms be on dedicated circuits, in one of two arrangements (pick one):

  • receptacles in a bathroom are on a dedicated 20A circuit that only serves receptacles in bathrooms.
  • receptacles in a bathroom are on a dedicated 20A circuit that only serves any load (lights, fan etc.) in that same bathroom.

Your setup is grandfathered since it predates this rule. However, you would break the grandfathering if you do too much work.

As such, if you have an existing receptacle in the bathroom, I would extend off its junction box for another receptacle in the same bathroom. If this circuit does not power any bathroom receptacles and your new receptacle won't be in the bathroom, then you can put "hot" with the existing blacks and "neutral" with the existing whites.

Otherwise you are not grandfathered and you need to pull a new circuit.


If you want to put another light off that same switch, it can either be powered off the existing lamp location, or this box. In this box, neutral goes to the neutral bundle, and switched-hot goes to the black-red wire nut.


Watch out for box cram/fill. If that's a 2-gang box, that's already pretty busy. Officially, count all wires except grounds as 1 each. Count all grounds together as 1. Count all cable clamps together as 1. Now count 2 for every switch or receptacle. Multiply by 2.0 if your wires are #14, or 2.25 if #12. You need that many cubic inches, and look inside the box for a stamped number stating cubic inches.

In your box I see 9 conductors + 1 (grounds) + 1 (cable clamps): 11. That is 22 cubic inches for #14 wire, or 24.75 cubic inches for #12.

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You didn't say how the wires are connected, and what is already in the junction box. I'm assuming there is already a switch in the junction box, and that the switch is connected to the black wirenut and the the red wire.

In all cases, the white wires all go to the same wire nut. However, your existing wirenut may not be larger enough for 4 wires. You would have to know the color of the wire nut and the gauge of the wires, then look up a wire nut table.

If you want the light fixture to be switched, then you connect the black wire from the light to the red wire. If you want the light to be on all of the time, then you connect the black wire of the light to the black wire nut. Again, make sure your wire nut is not too small.

  • Thanks! Purchased bigger wire nuts just for that. I just wasn't sure if 4 white wires can go together. I added a diagram in the post. – Andy Jan 25 '18 at 22:04
  • The color of the wire dosent matter it is the gauge of the wire 12 or 14 and the size of wirenut red, yellow, tan with this information we can look up the listing , I use tan and red or t/r+ they can handle 5 number 12 wires or 6 number 14 gauge wires, the package should say how many wires for that size. – Ed Beal Jan 25 '18 at 22:26
  • Great. But the wiring diagram makes sense - right? – Andy Jan 25 '18 at 22:38
  • It makes sense but your not saying where you are putting the receptacle. If you are in the US and if the receptacle is going in the bathroom, it needs to have its own 20A circuit. – Retired Master Electrician Jan 26 '18 at 7:55

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