Conductor sizing and ampacity on the Texas journeyman exam

Why this block decides the calculations score

Conductor sizing is where the Texas calculations portion is won and lost. Sixty-eight of the five hundred questions in our bank sit in this area, and the published content outline gives branch circuits and conductors four of the twenty-four scored calculation items plus ten of the fifty-six knowledge items. That is the heaviest tie on the knowledge paper.

The Texas journeyman exam is two separately scored papers taken in one sitting. NEC Knowledge is 56 scored items inside 59 sat, with 130 minutes on the clock. Calculations is 24 scored inside 26 sat, with 110 minutes. Each half passes at 70 percent on its own, so you can clear one and rebook the other. For fiscal 2025 TDLR reports 24.46 percent passing the knowledge portion and 20.56 percent passing calculations, out of 26,303 attempts across every Texas electrical exam that produced 6,181 passes.

The order these rules run in

Almost every wrong answer in this area comes from working the steps out of sequence. The order that holds is: pick the starting column by the insulation, apply ambient correction and conductor-count adjustment as multipliers, then check what the terminations allow, then check the overcurrent rule the conductor size triggers. Ampacity derating covers the middle step and termination temperature covers the one after it, and reading them in that order is worth more than reading either one twice.

The ten topics

• Derating is two multiplications and a separate check, and Texas exam items are built on the order. Both correction factors multiply, and the exam pays for knowing which column you started in.
• The termination check runs on a number the derating never touched, and it settles more items than the derating does. The 90 degree column gets you started and 110.14(C) decides what you are allowed to keep.
• Parallel questions are usually a division problem with a fraction planted in the options. Five conditions in 310.10(G), and the item usually breaks one of them on purpose.
• Voltage drop gets tested twice over, once as a question about status and once as arithmetic. An informational note that carries no requirement, asked as though it did.
• The neutral question gets answered before any table is opened, and the rest of the item rides on it. When the neutral counts, when it does not, and what a nonlinear load changes.
• The 240.4(D) small conductor cap, and how Texas exam items get built around it. 240.4(D) caps three wire sizes, and 240.4(B) is the permission people reach for too early.
• Cable types on the Texas exam, and the second lookup that decides the answer. Articles 320 through 340 by their letters, and which one the stem is describing.
• Continuous loads on the Texas exam, and the three places 125 percent comes from. Where 125 percent lands, where it is released, and the double count that costs the item.
• Conductor insulation types on the Texas exam, and the four decisions they make for you. The letter code decides four separate things, and only one of them is heat.
• Tap rules on the Texas exam, and the four questions that name the subdivision for you. Each permission in 240.21 charges a price, and the price is the part the item tests.

What carries weight and what does not

Two of these topics are lighter on the paper than their reputation suggests. Voltage drop lives in an informational note and carries no requirement, and thirteen of the sixty-eight bank items touch it, usually asking you to notice that it is advisory. Parallel conductors gets five items in this area and they almost always work by breaking one of the five conditions in 310.10(G) on purpose. Both are worth an evening each and no more.

The heavy ones are derating, terminations and the small-conductor rule. Thirty-seven of the sixty-eight carry an ambient or adjustment factor, sixteen touch the termination check, and 240.4(D) shows up in seven questions across two areas.

What moved for the 2026 edition

Texas adopted the 2026 National Electrical Code under 16 TAC 73.100, effective 1 September 2026, and the examinations follow the same date. Inside this area the change that bites is 310.15(E), which was restructured into a list with an exclusion, and 250.122(H), which sat at 250.122(F) in a 2023 book. The rule text held still in both cases and the address moved, so the habit that survives the edition change is finding a subdivision by its title.

As read on 24 August 2026 the PSI bulletin updated 9 July 2026 prints in capitals that the examinations reference the 2026 edition from 1 September, while the reference material list inside that same bulletin and the department examination page both still named the 2023 edition. We print the conflict because both documents are official and only one date can govern your appointment. Check your own admission notice.

What to do with this before test day

Work the ten pages in the order they are listed, then sit a timed set. The calculations portion gives you about 4.2 minutes an item measured on the twenty-six you actually sit, and a method that takes six minutes is a method that fails at the clock even when it reaches the right number. Thirty free questions, timed is enough to find out which of the two failures you have.

The worked arithmetic for each of these topics, step by step with the numbers shown, sits in the question set. These pages are about how Texas tests the topic. That one is about how the math runs.

Questions people ask

How many conductor sizing questions are on the Texas journeyman exam?

The published content outline gives branch circuits and conductors ten of the fifty-six scored items on the NEC Knowledge portion and four of the twenty-four on Calculations, which is fourteen scored items across the two papers. That is the heaviest area on the knowledge portion, tied with wiring methods and with equipment and devices. Our own five hundred question bank puts sixty-eight questions in conductor sizing, which is a deliberate overweight, because this is the block where a method error repeats across every item that uses it.

Do the ambient and conductor-count factors add or multiply?

They multiply, and both of them apply. A conductor with a base ampacity of 100 amperes in the 90 degree column, a 0.87 ambient correction and a 0.70 adjustment for conductor count lands at 100 times 0.87 times 0.70, which is 60.9 and rounds to 61 amperes. Every wrong answer offered on that kind of item is a version of the same mistake: 87 is the ambient factor alone, 70 is the adjustment alone, and 157 comes from adding the two factors to get 1.57 and multiplying once.

Does the 90 degree column mean I can load the conductor to that value?

The higher column gives you a starting ampacity for the correction and adjustment arithmetic. What you are allowed to keep is decided separately by 110.14(C), which looks at the temperature rating of the terminations at both ends of the circuit. Sixteen of the sixty-eight conductor questions in our bank turn on that check, and ten of them name a temperature column explicitly, so the item is usually testing whether you stopped after the derating step.

Which conductor topics are worth the least study time?

Voltage drop and parallel conductors. Voltage drop sits in an informational note and carries no requirement, so the question is often testing whether you know that. Parallel conductors gets about five items in this area, and they generally work by violating one of the five conditions in 310.10(G). Both reward an evening of reading and neither rewards a week. The time is better spent on derating, terminations and the small conductor rule in 240.4(D).

Did any conductor sizing sections move in the 2026 code?

Two that matter here. 310.15(E) was restructured into a list with an exclusion, and the equipment grounding conductor increase that a 2023 book carries at 250.122(F) sits at 250.122(H) in the 2026 edition. The rules themselves read the same. Because the addresses moved and the titles held, the habit worth building is finding a subdivision by its title in the table of contents, since the next cycle can renumber the letters again.