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I'm trying to add a new light fixture to an existing circuit with four fixtures already on it (let's call them #1-#4). I'd like the new light to branch off from #1, preferably without rewiring it "out and back" so that the new fixture becomes #2 (and #2 becomes #3, #4-->#5 etc). Can I simply tie the new fixture into the #1 box? I'm imagining this would look like a wire nut each for G/H/N combining: (a) incoming line, (b) outgoing line to new fixture, (c) outgoing line to #2 fixture, (d) pigtail to #1 fixture. Would this work? If not, please advise (preferably with diagrams!).

Additionally, looking inside the box for light #1 it looks wired in an odd way to me. Instead of pigtailing to the terminals from a wire nut, they connected two wires to each terminal. See attached photos. Should this be changed?enter image description hereenter image description here

Apologies for any fails, I'm a novice with electrical.

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It's hard to tell for sure but it looks like the double wires under the screw terminals may actually be single wires with a gap in the insulation. In other words, a wire comes in and connects to the screw terminal and then the same wire continues to the wirenut. If this is so, it's fine. If they are separate wires, then they should be separated, with one wire to the screw and the other wires connecting in the wirenut.

For your main question, you should be able to connect a third cable to this box to run to your new light. Add the black wire to the black wires in the wirenut; same with the white wires. For the ground, leave the old grounds twisted but cut off the very end (where it looks like its a single wire doubled back). Add the new ground to those in a new wirenut.

One kink is that you may exceed the fill limit on the box (I'll leave that question to the experts). You may need to replace the box with a deeper one.

Also, if that is #12 wire, a fourth wire will exceed the capacity of yellow wirenuts. It's ok with 4 x #14 wires but either way, you can replace them with red wirenuts.

By the way, if the existing wire is #12 and the breaker is 20 amps, you must continue using #12. If the breaker is 15 amps, you may use #14 but if it's #12 wire anyway, you should continue using #12 to avoid confusion.

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  • Thanks for this excellent and thorough answer! I checked and you are correct, it's a single wire loop under the screws. My only question with that is whether that means that if fixture #1 has an issue it will affect other fixtures downstream? Regarding box fill, it's a 2 1/8 round box, which from what I can Google seems compliant for 6 wires plus ground. But would welcome expert feedback. Confirmed on 15 amp breaker and all #14 wire.
    – yphraim
    Jul 24 at 13:10
  • @yphraim If the looped wire were to come loose from the fixture, the other fixtures would not be affected because the wire is still in one piece. On the other hand, if you had two wires under the screw and it came loose, the wires could separate and the later fixtures would go out.
    – DoxyLover
    Jul 25 at 5:58

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