I'm going to be running a new electrical line to a new shed. I opened up my breaker box and came across what's pictured below.
The top 20A breaker goes to our well pump, and the 15A goes to the shed. If I follow the wires, the neutral wire from the well pump (which is the back connection) connects to the 15A shed's breaker. Is that normal?
Your well pump is 240V. Cable comes black, white, ground and when you have a 240V only load, the white wire is a second hot. In conduit, you would use a hot color (2 blacks, or black & red, or one of the various other colors) but in cable, 2 conductors is black & white.
It should be "re-marked" with black or red tape or paint or heat-shrink, but it often isn't.
It should NOT be connected to two independent breakers. It should be connected to a dual-pole breaker which will be twice as wide as the single-pole breakers you show, and clip onto TWO of the bus wings.
[want proof? turn off your shed breaker and watch your well pump not run. But you might find power in the shed, to an extent (at least enough to shock you) if the well pump is trying to run, since power will pass through the motor windings (at half-voltage) and then to your shed circuit - this Not Good.]
So, buy a dual-pole breaker of the correct size for your pump, re-mark the white wire with red or black, and connect the well black and re-marked white to the two terminals on the new dual-pole breaker, leaving your shed circuit out of the well circuit.
You'll have a 20A single pole breaker (that you will remove the black pump wire from) to use for whatever new thing you are adding...
Obligatory reminder to use a torque screwdriver or wrench for tightening the terminal screws - values are on the box label, and molded into the breakers themselves (35 in-lb for the breakers, if I recall correctly)
Yes, the neutral being double-stuffed is wrong. Every neutral gets its own hole. Grounds may be able to share, that should be detailed on the panel label that also has the torques for the ground/neutral bar screws.
The well breaker should be a double-pole, probably 15 or 20 amps, size should be specified in the pump's documentation (if you have it or know what it is.) If it's not tripping the 15A shed breaker that feeds half of it, 15A might be sufficient (if documentation is missing.) Looks like you could put that on the bottom and move the shed up - or you can wire-nut an extension onto the well white to make it reach the top position. Breaker panels ARE junction boxes, though there's a common misconception that they are not.
You have a 240V pump misusing black and white as its wire colors and improperly fused.
It's also a weird, but not illegal multi-wire branch circuit... it has 2 trivial defects... it could be fixed, but it's a stupid design so we'll get rid of it.
First, the length of the "white wire" is a nothingburger. It is too short, yes, but it is trivial to extend it with a pigtail and a wire nut. Go to any hardware store that sells wire by-the-foot and get 1 foot of red #12 THHN wire. (an individual wire). You'll also need a yellow or red wire nut.
Also get a 5-pack of multi-colored electrical tape ($4-5). That white wire should have been marked black or a color to indicate it is a hot. Even though you're extending it, it still must be marked. Mark it red, since that most clearly indicates its function.
They should not have poached/tapped that other breaker like that. Instead of the $5 breaker they used, they should have bought a $10 HOM220 2-pole breaker. It is twice as wide. Install that in place of the breaker now there. The black and white-now-red go to this breaker.
Really, feel free to place any breaker in any position, to match up with whichever panel knockouts have been removed on the cover. If you need to knock one out, just choose carefully.
If you have any empty holes in the cover (because of too many knockouts being busted out), fill them. Stick your old 20A breaker there. If you need more, they're $5.
Lastly, correct the neutral-ground double-tap on the neutral bar. You can only put 1 neutral per screw. If you were crammed for space, you can buy accessory ground bars, or they allow some number (2 or 3) of ground wires to share a screw.
