Small Conductors Practice Questions

C. It is protected in accordance with its ampacity, unless one of the subdivisions of 240.4 says otherwise

The opening sentence sends you to the ampacity rules and then lists eight subdivisions that can change the answer. Reading only the subdivision you were looking for, without the sentence above it, is how candidates end up applying an exception to a conductor the exception never reached. Flexible cords, flexible cables and fixture wires are carved out of this section and answered in the next one.

NEC 2026 240.4

A. 20 amperes

The entry for 12 AWG copper is one of the five in the list that carries no conditions with it, so the figure stands on its own. The 25 ampere answer is the 75 degree column ampacity of that conductor and is the trap the entry exists to close. The cap is applied after any correction and adjustment factors, never before them.

NEC 2026 240.4(D)(6)

D. 15 amperes

This entry has no conditions attached and the figure applies wherever the conductor is not a tap and not one of the applications sent elsewhere by the table. The 20 and 25 ampere answers are the 60 and 90 degree column values for the same conductor. Neither of them survives the cap.

NEC 2026 240.4(D)(4)

B. 30 amperes

Another of the five unconditioned entries, and the one most often reached on a real job because 10 AWG lands right at the boundary of the sizes people run. The 35 ampere answer is the 75 degree column value and is what the arithmetic will hand you if you stop before the cap. The 40 ampere answer is the 90 degree column value.

NEC 2026 240.4(D)(8)

A. 15 amperes

Aluminum and copper-clad aluminum of that size share one entry and it is a step below the copper figure. The 20 ampere answer is the copper number and is what people reach for when they read the size and stop reading. Watching the material as closely as the size is the whole discipline in this list.

NEC 2026 240.4(D)(5)

C. 25 amperes

The aluminum entry sits one step under the copper one again, so the answer is not the 30 amperes people carry in their heads from the copper side. Two of the eight entries in the list are written to aluminum and copper-clad aluminum, and both of them are lower than their copper neighbors. Reading past the size to the material is what separates a right answer from a confident wrong one.

NEC 2026 240.4(D)(7)

B. After any correction for ambient temperature and any adjustment for the number of conductors

The subdivision says outright that the figures apply after those factors have been worked out, and that ordering is the whole point of the rule. It only ever cuts, so a derated ampacity landing above the limit does not raise the limit, it gets cut to it. Anyone who applies the cap first and then derates has done the arithmetic backward and will usually still arrive at a number that looks reasonable.

NEC 2026 240.4(D)

D. 240.4(E) and 240.4(G)

One sends tap conductors to the tap rules, the other sends specific applications to the articles that actually govern them. A candidate who learned the cap without those two will eliminate the right answer on any item that lands in either. That is why a stem naming a motor, an air conditioner or a tap and then offering the small conductor figure is the most attractive wrong answer in the topic.

NEC 2026 240.4(D)

C. 18 AWG copper, 16 AWG copper and 14 AWG copper-clad aluminum

Those three come with limits on how much of the load may be continuous and on what kind of overcurrent device or fuse class is protecting the conductor, and both parts have to hold. Quoting a figure from one of them without the conditions is a wrong answer that sounds authoritative. The five larger entries have no strings on them at all.

NEC 2026 240.4(D)(1), 240.4(D)(2), 240.4(D)(3)

B. Not more than 5.6 amperes

The figure is 80 percent of the 7 ampere limit, which is the familiar continuous load relationship written into the entry rather than left for you to apply. The second half of the condition names the overcurrent devices and the fuse classes permitted with the conductor, and both halves have to be met. An item that gives you 18 AWG and a continuous load is checking this number and nothing else.

NEC 2026 240.4(D)(1)

A. 10 amperes

This is the entry that surprises people, because 14 AWG copper is 15 amperes and the copper-clad aluminum of the same size is well below it and comes with conditions attached. The material changes the answer by more than one step here. It also picks up the same continuous load and device conditions the 16 AWG copper entry carries.

NEC 2026 240.4(D)(3)

D. No, since motor and motor control circuit conductors are sent to Article 430 by the table of specific conductor applications

The small conductor rule excepts that table at the top of the subdivision, so the cap never reached the conductor in the first place. Article 430 governs it, and the parts named in the table are where those rules live. The answer claiming control circuits have no overcurrent requirements overshoots, because they do have requirements, they are just somewhere else.

NEC 2026 240.4(G), Table 240.4(G)

B. Dwelling unit service and feeder conductors

Fire alarm, welder and air-conditioning conductors all appear in the table with the article that governs them printed alongside. Dwelling unit service and feeder conductors get their own subdivision at the end of 240.4 instead, which points at the dwelling service and feeder sizing rules. Two different relief valves, and knowing which one a stem is standing in front of decides the item.

NEC 2026 Table 240.4(G), 240.4(H)

A. Three

All three have to hold, and failing any one of them means rounding down rather than up. They cover the kind of branch circuit, whether the conductor ampacity already matches a standard rating, and a ceiling on the rating you select. Most people remember the permission and forget that it comes with strings.

NEC 2026 240.4(B)

C. A branch circuit supplying more than one receptacle for cord- and plug-connected portable loads

The reasoning is that nobody controls what gets plugged into those receptacles, so the conductor cannot be given a device larger than its own ampacity. A circuit supplying one piece of fastened equipment does not raise that concern. This is the condition of the three that an item is most likely to build a scenario around.

NEC 2026 240.4(B)(1)

D. 70 amperes, the next standard rating above the conductor ampacity

The standard ratings list runs 60 then 70, so 65 does not correspond to a standard rating and the second condition on the rounding permission is satisfied. The selected rating is nowhere near 800 amperes, so the third condition holds too. Nonstandard devices are permitted to exist, but the rounding rule is written against the standard list.

NEC 2026 240.4(B), 240.6(A)

A. 40 amperes

The 60 degree column gives 40 amperes, and 40 is itself a standard rating, so the second condition on the rounding permission fails and there is nothing to round up to. You take the 40. The 50 ampere answer is the 75 degree column value and is only available where the terminations are rated for it.

NEC 2026 240.4(B)(2), Table 310.16

C. Their ampacity has to be equal to or greater than the rating of the device

The permission reverses above that line, so a 1000 ampere device gets conductors with at least 1000 amperes of ampacity and no rounding is offered. Watch the boundary rather than the number, since the rounding rule allows a selected rating up to and including 800 amperes. An item that hands you a 1000 ampere scenario is checking whether you noticed you crossed it.

NEC 2026 240.4(C)

B. 275 amperes

The list runs 250 then 300 in that region and never prints 275. The other three are all on it, including 110, which candidates often assume is not standard because it is uncommon in the field. Answering a rounding question without the list open is how people talk themselves into a number that is not there.

NEC 2026 Table 240.6(A)

D. Their use is permitted

The section says outright that fuses and inverse time circuit breakers with nonstandard ratings may be used. The list defines what counts as standard for the purposes of the rounding rule and does nothing else. So a question asking what devices are available and a question asking what the next standard size is are different questions with different answers.

NEC 2026 240.6(A)

C. 1, 3, 6 and 601

Three very small ratings and one that sits just above the 600 ampere entry in the table. They exist because fuses are made in sizes that circuit breakers are not, and they matter on control and instrumentation work. An item that offers 601 amperes as a standard rating is testing exactly this sentence.

NEC 2026 240.6(A)

D. 30 amperes

Start at 40 amperes in the 90 degree column, apply the 0.80 adjustment for six conductors and you have 32 amperes, which is under the 35 ampere termination limit and so does not run into it. Then the small conductor cap takes the result down to 30. The 32 ampere answer is the correct arithmetic with the last step missing, and it is the one that catches people who did the hard part right.

NEC 2026 240.4(D)(8), 310.15(C)(1), Table 310.16

A. 20 amperes

The 90 degree column gives 30 amperes, the correction for that ambient is 0.91 and the adjustment for four conductors is 0.80, so 30 times 0.91 times 0.80 is 21.84 amperes. That is above the small conductor limit, so the limit cuts it to 20. Two factors applied correctly and the answer is still decided by the two-line rule at the end.

NEC 2026 240.4(D)(6), 310.15(B), 310.15(C)(1), Table 310.16

B. The rules on location in circuit, among five other listed places

A tap is protected by the tap rules rather than by its own ampacity, which is the entire reason those rules exist. The subdivision lists six destinations, and location in circuit is the one that covers ordinary feeder and branch circuit taps. Once a conductor is in that world, the small conductor cap is behind you.

NEC 2026 240.4(E)

D. Local restricted access, plus either equipment and software identified as evaluated for cybersecurity or a completed and documented cybersecurity risk assessment of the network

Local restricted access by one of the four listed methods comes first, and then the remote path adds its own condition. A nonnetworked local interface satisfies the second half on its own, while a networked one triggers the cybersecurity requirement. The section points at recognized standards without asking you to know their contents.

NEC 2026 240.6(D), 240.6(C)