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I have a junction box that seems to be wired as shown in the attached image, with the hot and neutral coming from two different wires out of the panel, and the other two wires spliced together inside the panel. If this is correct (I haven't removed the panel cover to look inside), why would it be done this way? Couldn't the splice be made inside the junction box instead? With only one wire to the panel?

I should note, there is more on this circuit than what is shown, but what is shown is complete (no other wires in this junction box, and the wires going to the panel run direct, not through any other boxes).

LEGEND
Marker: hot (black)
Pencil: neutral (white)
Highlighted: switched hot

enter image description here

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  • Is the switch in the diagram correlated to the light in the diagram?
    – isherwood
    Apr 5 at 19:14
  • And what are the highlighted wires connected to in the panel?
    – isherwood
    Apr 5 at 19:15
  • yes, the switch controls the light. the highlighted wires are what become hot when the switch is closed. I don't know what they are actually connected to inside the panel as I haven't opened the panel, I'm just assuming they must be joined together in some way Apr 5 at 19:23
  • Assuming the switch hots are just connected by a wire nut/connector in the panel(not on a breaker), then it is just odd. maybe a waste of wire not needed. You might also be missing another light(?) close to the panel that the switch also/or did control at one time.
    – crip659
    Apr 5 at 19:32
  • So the way you've drawn the switched hot traveling to the panel and back is not confirmed? I'd open the cover and confirm it before making further plans. It's very odd to do that. Really hard to imagine why.
    – jay613
    Apr 5 at 22:59

1 Answer 1

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As drawn, it will "work" but will violate a number of codes.

This can be readily seen by putting a clamp meter around either cable while a load is on the receptacle. You will get an amp reading - and you should always get an amp rating of zero in a cable! NEC 300.3 requires that all wires in a cable sum up to balanced (equal and opposite) current. That is for a bunch of reasons relating to the behavior of AC power.

200.7(C)(2) allows a white wire in a cable to be re-marked with tape, for use as a hot wire. (was that done?) However it says the white must be used for always-hot, and never for the switched-hot leg. In other words, the wire you highlighted can't ever be the white.

So, the white wire on the switch leg must be marked with black tape per 200.7.

I recommend also marking the black wire on the switch leg with red tape (a preferred color for "switched-hot") and the same to the black wire on the lamp leg.

On the panel cables, de-commission the right side cable. Land the left side white on the neutral bar.

Then in the junction box, it's just a matter of matching up "like" colors (with tape color overriding natural color): White to white, red to red, and black to black. The switched-hot will now go straight from the switch-leg red to the lamp-leg red, and won't take a trip to the panel.

The left side panel cable will carry all current so will be balanced.

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  • Thanks everyone. I'm not planning to change anything until I look in the panel, or get a professional. I'm hoping once I look inside the panel that will shed some light on why it was done this way, it just seems so odd, especially since the box is only 2ft from the panel. What I do know is that if I disconnect every wire inside that junction box, the hot and the neutral are from different cables, and both of those cables run to the panel. I found the hot by measuring all of the wires against the grounded metal box. I then measured the hot against each of the other wires to find the neutral. Apr 5 at 23:57

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