Termination Temperature Practice Questions

A. The largest current in amperes a conductor carries continuously, in the conditions it is installed in, without going past its temperature rating

Two phrases in that definition carry the weight. Continuously rules out momentary current, and under the conditions of use is what pulls in ambient temperature and the number of conductors bundled together. Notice the device rating is nowhere in it, which is why an ampacity question and an overcurrent question are two different questions even when they land on the same conductor.

NEC 2026 Article 100

B. The lowest temperature rating of any connected termination, conductor, or device

The rule names three kinds of part and takes the lowest of them, so a lug, a breaker and the wire itself are all candidates. The insulation rating is only the answer when it happens to be the smallest of the three, which on ordinary gear it almost never is. Reading it as an insulation rule is how a candidate ends up sizing off the 90 degree column on equipment that cannot take it.

NEC 2026 110.14(C)

C. The 60 degree column

This is the lower of the two doors into the section and it opens on the 60 degree column. The word or matters: the ampere rating is one trigger and the conductor marking on the equipment is a separate one, so a stem that gives you the terminal marking has handed you a route into the rule whether or not the ampere figure agrees.

NEC 2026 110.14(C)(1)(a)

D. The 75 degree column

The upper subdivision defaults to 75 degrees, and it too has the two independent triggers. A 60 ampere disconnect whose lugs are marked for conductors larger than 1 AWG lands here on the marking alone, even though its ampere rating would have pointed at the other subdivision. Sorting on the ampere figure by itself is the mistake this pair is built to catch.

NEC 2026 110.14(C)(1)(b)

A. Ampacity adjustment, correction, or both

The section says so in its own opening sentence, which is what makes 90 degree insulation worth buying. You start from a bigger number and let ambient and conductor count eat into it before the termination check happens. It buys nothing where there is no derating to do, because with no factors applied the termination column is what you land on anyway.

NEC 2026 110.14(C)

B. The ampacity at the listed and identified temperature rating of the connector

A connector bought and installed apart from the equipment carries its own listing, and the conductor is held to what that connector is listed for. This is the honest route to a 90 degree termination in the field, and it is a listing question rather than a wire question. The subdivision sits in its own paragraph precisely because it is not tied to the 100 ampere split above it.

NEC 2026 110.14(C)(2)

C. Table 310.16, as appropriately modified by 310.12

The section names one table and one modifier. Table 310.16 is the raceway and buried table, and 310.12 is the dwelling service and feeder allowance that lets certain conductors be read at a reduced figure. Reaching for the free air table because the conductors are in free air somewhere in the run does not change what the terminations are judged against.

NEC 2026 110.14(C)(1), 310.12

D. Identified for the specific conductor class or classes

Fine stranded conductor is what welding cable, generator leads and many battery connections are made of, and an ordinary set screw lug is not built to hold it. The classes themselves are shown in Chapter 9 Table 10. This sits in the opening paragraphs of the section rather than under temperature, which is why a candidate who only reads the temperature subdivision has never met it.

NEC 2026 110.14

A. 54.6 amperes

Start at the conductor rating: 6 AWG copper is 75 amperes in the 90 degree column. Correct for a 36 to 40 degree ambient at 0.91 to get 68.3, then adjust for four current carrying conductors at 0.80 to get 54.6. The termination limit is the plain 65 amperes in the 75 degree column with no factors on it, and 54.6 is the smaller of the two, so it wins.

NEC 2026 Table 310.16, Table 310.15(B)(1)(1), Table 310.15(C)(1), 110.14(C)

B. Conductors rated 75 degrees or higher, with the ampacity not exceeding the 75 degree value

This is the fourth item in the lower subdivision and most candidates have never read it. It lifts a motor circuit off the 60 degree column and up to 75 without needing the equipment to be listed and identified for anything. A stem that names a design letter is pointing straight at it, which is the only reason the letter is in the stem.

NEC 2026 110.14(C)(1)(a)

C. 2 AWG

The circuit is 100 amperes or less, so the answer comes out of the 60 degree column no matter what the jacket says. There 3 AWG is 85 amperes, which will not carry 90, and 2 AWG is 95, which will. Sizing from the 90 degree column gives 4 AWG at 95 amperes and reads as a tidy answer, which is exactly why it is sitting in the options.

NEC 2026 110.14(C)(1)(a), Table 310.16

D. 3/0 AWG

Over 100 amperes puts you in the 75 degree column, where 3/0 copper is exactly 200 amperes and 2/0 is 175. No correction applies at 30 degrees and no adjustment applies to three conductors, so the table figure is the answer with nothing done to it. Going up to 4/0 is not wrong on the wire, it is just larger than the code asks for and costs a mark.

NEC 2026 110.14(C)(1)(b), Table 310.16

A. The equipment is listed and identified for use with conductors of that rating

The permission attaches to the equipment and to its listing, not to the wire. A number stamped near a terminal is a marking and not a listing, and the general rule applies unless the equipment is listed and marked otherwise. Most ordinary breakers, panelboards and safety switches are 75 degree equipment at best, so a stem that describes plain gear has already answered this without saying so.

NEC 2026 110.14(C)(1)

B. 25 amperes

Work it in order. The 90 degree aluminum figure of 35 amperes adjusts at 0.80 for four to six conductors and gives 28, and the 75 degree termination figure of 30 is larger, so 28 is the usable ampacity. Then the small conductor rule caps the device for 10 AWG aluminum at 25 amperes, applied after the correction and adjustment factors. The cap is the answer, not the 28.

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

C. No, the termination figure is read with no factors applied to it

Correction and adjustment belong to the conductor at its own rating. The termination figure is a plain table lookup that stands as printed, and the usable ampacity is whichever of the two comes out smaller. Applying the factors twice produces a number below what the code asks for, which oversizes the conductor and reads as the safe answer. It is still wrong.

NEC 2026 310.15(A), 110.14(C)

D. 180 amperes

The 90 degree aluminum figure for 4/0 is 205, but nothing derates it here, so there is no headroom to spend. The circuit is over 100 amperes, which puts the terminations in the 75 degree column at 180 amperes, and that is the smaller number. The XHHW-2 rating has done no work at all in this problem, which is the point of the item.

NEC 2026 Table 310.16, 110.14(C)(1)(b)

A. 24.4 amperes

Take 40 amperes from the 90 degree column, multiply by 0.87 for a 41 to 45 degree ambient in the 90 degree correction column, and multiply again by 0.70 for seven to nine conductors. That is 24.4 amperes. Starting from the 75 degree column and using its correction factor gives about 20.1, and it is wrong twice over: wrong column and wrong correction factor for the insulation you actually installed.

NEC 2026 Table 310.16, Table 310.15(B)(1)(1), Table 310.15(C)(1)

B. The 75 degree column, because the marking is an independent trigger

Each subdivision names two ways in and they are joined by or, so either one is enough on its own. The ampere rating here points at the lower subdivision and the conductor marking points at the upper one, and the marking carries it. This is why the terminal marking in a stem is never scenery, and why reading only the ampere figure hands you the wrong column.

NEC 2026 110.14(C)(1)(b)

C. 40 amperes

The conductor side gives 55 amperes at 90 degrees corrected by 0.82 for a 46 to 50 degree ambient, which is 45.1, with no adjustment for three conductors. The termination side is the plain 60 degree figure of 40 amperes. Take the smaller, which is 40. Multiplying the 40 by the correction factor to get 32.8 applies a factor where none belongs and is the trap the fourth option collects.

NEC 2026 110.14(C)(1)(a), Table 310.16, Table 310.15(B)(1)(1)

D. It reduces the ampacity of the conductor itself

A 90 degree conductor stays a 90 degree conductor. Its insulation is unchanged and so is the current it can carry, and the section limits only the figure you are allowed to carry forward when you size against the load and the device. Holding that distinction is what lets you use the big column for the factors and the small one for the check without confusing the two.

NEC 2026 110.14(C)

A. 10 AWG or smaller

The terminals subdivision sets that size limit and it is easy to miss because most reading of this section stops at temperature. Above 10 AWG the connection is made with a pressure connector, a solder lug or a splice to flexible leads. A terminal that takes more than one wire, and any terminal used with aluminum, each have to be identified for that duty, which is a separate sentence worth carrying.

NEC 2026 110.14(A)

B. From the equipment markings or the manufacturer installation instructions

The section points at the equipment and at the instructions that came with it, and it requires an approved means to actually reach the stated value. That last clause is the enforceable half: knowing the number does not satisfy it if nothing on site can apply it. The informational notes name torque tools and shear bolt style fasteners as examples of an approved means.

NEC 2026 110.14(D)

C. 60 amperes

Standard ratings run 50, 60, 70 in that stretch, so 54.6 falls between two of them and the permission lets you take the next one up, which is 60. Three conditions ride with it: the conductors are not part of a branch circuit supplying more than one receptacle for cord and plug connected portable loads, the ampacity does not correspond to a standard rating, and the selected rating does not exceed 800 amperes.

NEC 2026 240.4(B), Table 240.6(A)

D. 110 amperes

Exactly 100 amperes falls inside the words 100 amperes or less, so you are in the 60 degree column, where 1 AWG copper is 110 amperes. The device rating is not the answer to an ampacity question; it is only what the conductor has to be able to carry. Reading 130 out of the 75 degree column is what an installer does when the wire is marked THHN and the gear is not listed for it.

NEC 2026 110.14(C)(1)(a), Table 310.16

C. The device has to be identified for the purpose and conditions of use

Conductors are not intermixed in a terminal, splicing connector or soldering lug where dissimilar conductors touch unless the device is identified for it. Size and temperature rating do not cure it, and neither does a compound: any compound used has to itself be identified for the use and be a type that will not harm the conductors or the equipment. The identification lives on the device.

NEC 2026 110.14