Took me a little while but I went thru the 2024 NEC code book. It's over 900 pages and picked out some of the relavent sections.
First a little on the way power is distributed and the nomenclature used. Electricity comes from the power company "POCO". From the POCO transformers it goes thru the service conductors (wires) to the Service Disconnect. That would be your main breaker. Then it goes thru the feeder conductors to individual disconnects. These would be the individual breakers. Finally the power goes thru the circuit conductors thru a switch or control mechanism to the load. 120 volt circuits require 1 power conductor, 1 neutral conductor, and 1 equipment grounding conductor. 208 and 240 volt single phase loads have 2 power conductors , do not need a neutral conductor, and 1 equipment grounding conductor. 3 phase loads have 3 power conductors and 1 equipment grounding conductor. The neutral conductor and equipment grounding conductor are separate circuits from the load all the way back to the service disconnect. There and only there they are bonded together. Clear as mud?
Now assume we are running a 230 volt single phase pump & motor from the main panel in the house. Usually this is a 200 amp service. The 200 amp breaker is the service disconnect. The buss bars in the panel serve as the feeders. We then have a two pole breaker as a disconnect for the pump circuit. We run two 120 volt circuit conductors and an equipment grounding conductor to the pressure switch and then to the pump control box. From the pump control box we are then going to run 3 power conductors and an equipment grounding conductor to the well and down the well to the pump motor. Why 3 power conductors from the control box to the pump motor? We need that extra conductor for the start winding to get the motor started.
NEC 210.64 and 210.50G2 require a 120 volt outlet at the electrical equipment. NEC 110.34 and 210.70C require a switched light illuminating the electrical equipment. That would be the service disconnect and breakers, the main device panel. Also the pressure switch and control box. So light and 120v outlet wherever the disconnecting means, pressure switch and/or control box are located.
NEC 250.52A8 requires that any metal water pipe and the well casing, if it is metal, to be grounded to the electrical grounding conductor.
Now let's move our pressure switch, pressure tank, and control box from the house our to the garage, barn, shop, pump house, actually any auxiliary building or structure. Now we've got a feeder circuit from the main service disconnect to the building. NEC 225.30 states that an auxiliary building or structure can only be fed by one feeder or branch circuit. Now we have to have a sub panel in this building. We have to have power for the pump. I've already cited the sections of the code that require a light and a 120 volt outlet in the pump house. Now we also have to have a light over the outside door. This is i. NEC 210.70A2. We've ended up needing a feeder circuit to pump house for both 120 volts and 240 volts. How many conductors do we need now? We need the 2 120 volt feeders. 1 neutral conductor for 120 volt circuits and 1 equipment grounding conductor. A total of 4 conductors. But wait, were not done. Since this is an anadditional building we have to add additional grounding. 2 grounding rods or plates, a ground loop wire, or grounding to the rebar in the concrete floor or foundation.
These are some, but in no way all, of the applicable sections of the NEC electrical code. Did I mention that those 12 volt outlets need to be gfci protected? If an outlet is outside it needs to be marked TR, tamper resistant and WR weather resistant? I could go on and on and on........