Ten prompts on a clock. Each one names a conductor size, a material and a temperature column, and you pick the ampere figure out of four. Every number comes from NEC 2026 Table 310.16 and the 240.4(D) caps, printed in full further down.
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Levels one and two ask for the printed cell. Level three mixes the two materials and, when the size is 14, 12 or 10 AWG, asks what the overcurrent device is held to instead, which is the 240.4(D) figure and not the table figure.
The exam hands you the code book, so nothing here is about memorizing amperes. What costs time is the search: finding the right half of the table, then the right row, then the right column, under a clock that is running on 80 other questions.
Ten prompts is roughly what one calculation question costs you in lookups. Run a level until the search stops feeling like a search, then go read ampacity derating for what happens to that cell afterward.
Table 310.16 gives the ampacity of insulated conductors in a raceway, in a cable or directly buried. It is written for not more than three current-carrying conductors at an ambient of 30 degrees C, and 310.14 is the section that sends you to it.
The rows are conductor sizes, 14 AWG up through 1000 kcmil on this page. The columns come in two blocks of three: copper on the left, aluminum on the right, each split into 60, 75 and 90 degree ratings. Six numbers on a row, and the exam is testing whether you can pick the one it asked for.
Which column depends on two things and people usually stop after the first. The insulation sets a ceiling, so a 90 degree conductor may be read in the 90 degree column. Then 110.14(C) requires the ampacity to be coordinated so that it does not exceed the lowest temperature rating of any connected termination, conductor or device, which on circuits rated 100 amperes or less normally means the 60 degree column and above that the 75 degree column.
That is why the 90 degree column is the one people misuse. It is a real ampacity and it is the right starting point for ambient correction and conductor count adjustment, but it is rarely the number a breaker gets sized from.
Then there is 240.4(D). For the small sizes the overcurrent device has a ceiling of its own, and it applies after any correction for ambient temperature and for the number of conductors has been made. Level three of the sprint asks for that ceiling on 14, 12 and 10 AWG rather than for the table cell.
The trap the exam sets is a question that gives you a 90 degree conductor on a 20 ampere circuit and waits to see whether you answer 30. The order that keeps you out of it is fixed: find the cell, apply corrections, check the terminations, then check 240.4(D) last.
The sprint shows 12 AWG copper and the 90 degree column, and asks what the overcurrent device is held to. Table 310.16 gives 30 amperes in that cell, and 30 is on the option list, because a wrong answer that is not tempting teaches nothing.
The answer is 20 amperes. 240.4(D) holds the device on 12 AWG copper to 20 amperes once corrections for ambient temperature and for the number of conductors have been applied, so the 30 in the table is the ampacity of the conductor rather than the rating of its protection.
Notice that 20 is also what the 60 degree column prints for that row. That is true for all five capped sizes on this page, which is a useful check and a poor substitute for reading 240.4(D), because the two figures agreeing here is a fact about these rows rather than a rule.
The value used for your inputs is read from NEC 2026 240.4(D) and Table 310.16, the way you would read it in the exam room, and the working above names the row it came from. The tables themselves belong to NFPA and are not printed on this page. Bring your own copy of the 2026 code, which is what the exam requires anyway, and check the row there.
On a narrow screen the table scrolls sideways to reach the aluminum columns. The aluminum column covers aluminum and copper-clad aluminum. The printed table also carries a 14 AWG aluminum line, footnoted so that it applies only to copper-clad aluminum and only for ampacity adjustment or correction. Those entries are left off this page and out of the game.
It gives the ampacity of insulated conductors run in a raceway, in a cable or directly buried, with not more than three current-carrying conductors and an ambient of 30 degrees C. The rows are conductor sizes and the six columns split copper from aluminum, then split each of those into 60, 75 and 90 degree ratings. Most branch circuit and feeder questions on the exam begin by landing on one cell of this table.
Start with the insulation, because the column has to match the temperature rating of the conductor you actually have. Then read 110.14(C), which says the ampacity has to be coordinated so it does not exceed the lowest temperature rating of any connected termination, conductor or device. That usually pulls you back to the 60 degree column on circuits rated 100 amperes or less and to the 75 degree column above that, which leaves the 90 degree column for correction and adjustment.
Because 240.4(D) sets a ceiling on the overcurrent device for small conductors, and for 12 AWG copper that ceiling is 20 amperes. The ceiling applies after any correction for ambient temperature and for the number of conductors has been made, so it is the last word rather than the first. The 30 in the 90 degree column is a real ampacity, it is just not the figure the device gets sized to.
On the copper side 14 AWG is 15 amperes, 12 AWG is 20 and 10 AWG is 30. On the aluminum side 12 AWG is 15 amperes and 10 AWG is 25. Those five figures are what the mixed level of this game asks for, and the cap table further down the page prints the same five rows.
The printed table does carry entries on that line, but they are footnoted twice: they apply only to copper-clad aluminum, and they are for ampacity adjustment or correction only. This page leaves that line out rather than print figures that carry conditions, so the aluminum rows here start at 12 AWG and the game never asks for a 14 AWG aluminum cell.
Two corrections, and they multiply together. 310.15(B) corrects for an ambient other than 30 degrees C, and 310.15(C)(1) reduces the ampacity of each conductor when more than three current-carrying conductors share a raceway or a cable. This game asks only for the printed cell, because that cell is the figure both corrections are applied to.
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