Neutral to Ground Bond Practice Questions

C. At one point, by the main bonding jumper at the service disconnect

One connection, made inside the service disconnect enclosure, and the rule that puts it there names the main bonding jumper by that title. Everything downstream of that point keeps the two apart. Options that add a second tie describe the exact condition the load side rule was written to stop.

NEC 2026 250.24(C)

A. Unspliced

A splice is a point of failure in a conductor whose only job is to hold when something else has already gone wrong. If the jumper opens, the enclosure loses its reference to the grounded conductor and the fault path goes with it. Continuous and identified are real code words, but neither is the one used here.

NEC 2026 250.24(C)

D. Nothing beyond carrying current, except where Article 250 itself permits otherwise

The rule bars connecting it to normally non-current-carrying metal parts, to equipment grounding conductors, or back to ground past that point. The escape hatch is narrow and lives inside the same article rather than in field practice. Answers that attach a size or a voltage to the bar are inventing a threshold that is not printed.

NEC 2026 250.24(B)

B. 250.30(A)(1) and 250.32(B)(1) Exception No. 1

One covers the single point where a separately derived system gets its own bond, the other covers a second building wired under an older edition. Both are places where the connection is legitimate rather than accidental. Learning the pair as a pair keeps you from arguing your way into a third one.

NEC 2026 250.142(B)

A. A component of the effective ground-fault current path that connects the grounded circuit conductor to the equipment grounding conductor, the supply-side bonding conductor, or both, at the service

The definition puts the jumper inside the fault current path rather than inside the grounding electrode system, which is the distinction most of the article turns on. A conductor to the electrode is the grounding electrode conductor and has its own definition and its own sizing table. The green screw is one permitted form of the jumper, not the definition of it.

NEC 2026 Article 100

C. The system bonding jumper

At a separately derived system the connection between the grounded conductor and the fault path is the system bonding jumper. The main bonding jumper is the same job done at the service. An equipment bonding jumper ties equipment grounding conductors together, and a supply-side bonding jumper runs on the line side of the service or system disconnect.

NEC 2026 Article 100, 250.28

B. Yes, routed with the ungrounded conductors to each service disconnecting means and landed on its grounded conductor terminal or bus

The requirement is written to the system being grounded, not to the loads, so the absence of a neutral load changes nothing. The same subsection then calls for a main bonding jumper connecting that conductor to each service disconnect enclosure. This item catches people who think of the grounded conductor as a load conductor and nothing else.

NEC 2026 250.24(D)

D. A grounded conductor goes in each raceway, connected in parallel, and none of them is smaller than 1/0 AWG

Each raceway gets one, they are joined at both ends like the ungrounded conductors, and the size comes from the table used for bonding jumpers with a hard floor underneath it. The floor is what the item is really testing, because the table alone can hand you something smaller. Dividing the load by the number of raceways is the shortcut the rule is written against.

NEC 2026 250.24(D)(2)

C. Copper, aluminum, copper-clad aluminum or another corrosion-resistant material, as a wire, bus, screw or similar conductor

The section is generous about material and form and strict about everything else, which surprises candidates who expect a short list. Corrosion resistance is the property being required, since the jumper has to still be a conductor years after anyone last looked at it. The screw is on that list by name, and that is why the little green one in a subpanel exists at all.

NEC 2026 250.28(A)

B. A green finish that stays visible with the screw installed

The marking rule exists so the next person opening the enclosure can tell at a glance that the screw is doing a job. A finish under the head would be useless for that, so the code asks for one that shows. Nothing in the section rates the screw in amperes or dictates the alloy.

NEC 2026 250.28(B)

A. Table 250.102(C)(1)

The jumper is sized as a bonding conductor, so it comes from the bonding jumper table and not from the grounding electrode conductor table. Table 250.66 covers the run to the electrode, which is a different conductor doing a different job in the same enclosure. Getting these two confused is one of the most common errors in Article 250.

NEC 2026 250.28(D)(1)

D. The largest ungrounded service conductor serving that particular enclosure

Each enclosure is treated on its own, so a small disconnect in the group does not get a jumper sized for the whole service. The rule reads that way because each jumper only ever carries fault current returning through its own enclosure. Adding the sets together is the move the subsection was written to head off.

NEC 2026 250.28(D)(2)

B. At any single point on the system from the source to the first system disconnecting means or overcurrent device

The installer picks the point and the code holds them to picking only one. Bonding at the source and again at the panel builds the same parallel path that the load side rule exists to prevent, one transformer further downstream. The word single is the whole answer, and the word unspliced is riding along with it.

NEC 2026 250.30(A)(1)

A. It is treated the same way as a grounded conductor downstream of a service, meaning no reconnection to metal parts, to equipment grounding conductors, or to ground

The bar is written into the same subsection that permits the system bond, using nearly the wording of the service rule. So a panel fed from a transformer is separated, and a panel fed from that panel is separated too. Anyone who thinks the separation rule belongs only to services will bond twice on the first job with a transformer in it.

NEC 2026 250.30(A)

C. An equipment grounding conductor, connected to the enclosure containing the building disconnecting means and to the grounding electrode conductor

The equipment grounding conductor goes with the feeder and is sized from the equipment grounding conductor table. That is the same answer you would give for any feeder, which is what makes the second half of the topic the harder half. The old practice of using the grounded conductor for this job survives only for work done under an earlier edition.

NEC 2026 250.32(B)(1)

D. It is left connected to neither the equipment grounding conductors nor the grounding electrodes at that building

The building gets its own grounding electrode system and does not get a second neutral bond, and those two facts sit one sentence apart in the same subsection. An item usually hands you both halves and expects you to keep them separate. The exception that allows the old bond reaches only installations made in compliance with earlier editions.

NEC 2026 250.32(B)(1)

A. Yes, with a narrow relief where only a single branch circuit, including a multiwire branch circuit, supplies it and that circuit carries an equipment grounding conductor

The general answer is yes, and the exception is written around the smallest possible supply rather than around the size of the building. A multiwire branch circuit still counts as a single branch circuit for this purpose, which is the detail the option is built on. Ampere thresholds and occupancy do not appear in the rule.

NEC 2026 250.32(A)

C. To the equipment grounding conductor in the circuit

For new work the answer has one part and no options in it, and the three-wire cord is not among them. The old allowance still exists but it is written to existing branch circuit installations only. Reading the stem for the word new or existing before you look at the choices settles most items in this corner of the article.

NEC 2026 250.140(A)

B. 120/240 volt single-phase three-wire, or 208Y/120 volt derived from a three-phase four-wire wye system

Two named circuit types and nothing else, and both of them carry a neutral at 120 volts to ground. That is the point, because the conductor being asked to do double duty has to be one that stays near ground potential. A stem that names any other system has already failed the condition before you reach the rest of the list.

NEC 2026 250.140(B)(1)

D. No smaller than 10 AWG copper, or 8 AWG aluminum or copper-clad aluminum

A conductor being asked to carry fault current back as well as neutral current gets a floor under it that an ordinary neutral does not have. The aluminum figure is one size larger than the copper figure, which is the pattern all through Article 250. Sizing it on the calculated load alone is exactly what the floor is there to override.

NEC 2026 250.140(B)(2)

C. On the supply side of, or within the enclosure of, the ac service disconnecting means

The permission is written to three locations and all three are on the line side of a bond rather than past it. Two of them cover a separate building and a separately derived system, and the third is the service itself. Every wrong answer in this family names a place that is downstream of a bonding jumper, which is the one place the connection is barred.

NEC 2026 250.142(A)

D. Neutral current divides between the neutral conductor and the equipment grounding conductor and any metal in its path

Two conductors joined at both ends are in parallel, so the return current splits between them by impedance whether anyone intended that or not. Nothing trips, because the total current going out still matches the total coming back. The result is current on enclosures and piping that are supposed to sit at zero volts, which is why the rule is a bar and not a preference.

NEC 2026 250.24(B), 250.142(B)

A. Not permitted, since each grounded conductor terminates in an individual terminal not also used for another conductor

Lifting one circuit for work would open the return of the other one while it is still energized, which is the hazard the rule removes. The only exception covers the grounded conductors of circuits with parallel conductors, and it needs a terminal identified for more than one conductor. Being on the same phase makes the situation worse rather than better.

NEC 2026 408.41

B. On a grounding terminal bar secured inside the cabinet and bonded to the cabinet and frame

Article 408 gives the equipment grounding conductors a bar of their own and requires it to be bonded to the metal it is protecting. Landing them on a grounded conductor bar is permitted only where that bar is identified for the purpose and where Article 250 allows the two to be interconnected there. In a subpanel Article 250 does not allow it.

NEC 2026 408.40

D. The first panel of a separately derived system, whose bonding is done with a system bonding jumper

A separately derived system is a power supply output other than a service with no direct connection to circuit conductors of another system, which is exactly what a transformer with an isolated secondary produces. Service equipment is defined by its connection to the serving utility, and nothing installed inside the building creates that. So the bonding question is answered from the separately derived system rules rather than the service rules.

NEC 2026 Article 100, 250.30(A)(1)