Sizing the equipment grounding conductor for the Texas exam, in the order that keeps you out of the traps

Where this conductor shows up

This is the busiest conductor in the bank. Fifty-one of the 500 items name it, spread over four areas: 32 in grounding and bonding, 9 in conductor sizing, 5 in conduit and box calculations, 5 in wiring methods. It reaches you on both portions of the exam.

What it does in each place differs, and candidates who learn one treatment carry it into the wrong item.

• In a sizing item it takes its size from Table 250.122 on the device rating ahead of the circuit.
• In an adjustment item it carries no current in normal operation, so 310.15(F) leaves it out of the current-carrying count.
• In a raceway fill item it occupies area and goes into the total like any conductor.
• In a box fill item up to four share a single volume allowance sized on the largest, and each one after the fourth adds a quarter.

Those four treatments look contradictory and answer four different questions. An item that drops a bare grounding conductor into a nearly full raceway is built on exactly that, with the fill failing while the adjustment count holds where it was.

The input is the device rating

A wire-type equipment grounding conductor of copper, aluminum or copper-clad aluminum takes its size from Table 250.122, entered on the rating of the overcurrent device ahead of the circuit (NEC 250.122). That one number is the entire input, and the load, the conductor size and the service size all sit outside it.

The reason is in the job: it has to hold together long enough for that specific device to open.

The row you land on prints separate figures for copper and aluminum, and the aluminum figure is larger all the way down, because aluminum has more resistance per foot at a given area and more conductor is needed to carry a fault for the time the device takes to clear it. Aluminum is permitted here, subject to restrictions on where bare and covered aluminum may be installed, so an item on it is a sizing question with a permission-flavored distractor.

Look the values up in your own code book. The table's short, it deserves its own tab, and it sits several pages from the grounding electrode table people confuse it with.

The cap that saves the answer

An equipment grounding conductor is capped at the size of the circuit conductors in the raceway or cable supplying the equipment (NEC 250.122). In the 2026 edition that subdivision is titled Not Larger Than Circuit Conductors and stands first in the section at 250.122(A).

The cap exists because the table on its own can produce an absurd answer, since the fault current reaching this conductor can never exceed what the circuit conductors deliver to the fault.

A second cap lives further down the section and makes a different comparison, so keep them apart. The general cap looks at the circuit conductors supplying the equipment, and the parallel cap at 250.122(H) looks inside one raceway at its largest ungrounded conductor.

When it gets upsized

Increase the ungrounded conductors for any reason beyond the ambient correction in 310.15(B) or the conductor-count adjustment in 310.15(C), and the wire-type grounding conductor goes up in proportion to the increase in circular mils.

So upsizing for voltage drop carries the grounding conductor up with it, and upsizing because a run is hot or crowded leaves it where the table put it. There's a physical reason for the split. Correction and adjustment are about shedding heat over the same distance, while voltage drop upsizing happens because a run is long, and length is what raises the impedance of the fault loop.

Proportional means circular mils, and this is where candidates lose the item. Moving the grounding conductor by the same number of AWG sizes fails, because the steps between sizes are uneven, so two sizes near the small end is a very different ratio from two near the large end. What works is to find the ratio the ungrounded conductors grew by, apply it to the tabulated area of the grounding conductor, and take the first size at or above the result.

Old study material is dangerous here, because the previous wording turned on whether the conductor was larger than the minimum with sufficient ampacity, which gives a different answer on a derating item. Our conductor sizing hub works the ratio arithmetic.

Parallel runs and the fraction trap

The subdivision titled Conductors in Parallel, at 250.122(H) in the 2026 edition, splits on geometry first. Where the conductors are decides how many grounding conductors you install, and the single device ahead of the run decides the size of every one.

• Paralleled in the same raceway, auxiliary gutter or cable tray: one wire-type conductor is permitted, sized on the device for the feeder or branch circuit.
• Paralleled in multiple raceways: a wire-type conductor goes in each and they connect in parallel, each sized on that same device rating.
• Multiconductor cables paralleled: the grounding conductor in each cable sizes on the device rating, and they connect in parallel.

The per-raceway cap then lands on top, holding the conductor in each raceway at the largest ungrounded conductor in that raceway. So on a paralleled feeder the answer's bounded twice, once by the table at the device rating and once by the phase conductor beside it.

The wrong answers on a parallel item are almost always fractions. Divide the device rating by the raceway count, or divide the table result by it, and your number's printed on the sheet waiting. The size never becomes a share of that rating.

When the path is a raceway

The Article 100 description is a conductive path that's part of an effective ground-fault current path, so a wire is one way to build it and the code accepts others. 250.118 is the list, raceways and cable armor are on it, and a circuit with no green wire can still have a complete equipment grounding conductor.

The flexible types carry conditions on top of being listed. 250.118 attaches a limit on the length of the ground return path, a limit on the device rating ahead of it, and a bar on relying on the conduit where flexibility is needed after installation. A spiral wound path has more impedance than a solid one, and a connection installed to absorb motion gets flexed for the life of the equipment, so a motor whip that moves gets a wire pulled through.

Two things people reach for sit off the list. A structural steel frame is metal the code requires to be bonded under 250.104(C), and that places a duty on the building without turning it into a circuit component, because continuity through a bolted structure survives nobody's renovation schedule. The earth is off the list for the reasons worked through on grounding compared with bonding.

The box rules that catch people

Four rules govern the box, and each has an item built on the field habit it forbids.

• 250.148 joins the equipment grounding conductors in a box so that removing a receptacle, luminaire or other device leaves grounding continuity intact. Carrying them through the device strap looks tidy and makes every outlet downstream depend on the one device somebody's about to unscrew.
• 250.148(C) connects a metal box itself to those conductors by the methods 250.8 names, which is the job the green screw in the tapped hole does. A connector clamping a nonmetallic sheath brings no metal path with it.
• 250.146 runs a jumper from the receptacle grounding terminal to a grounded box as the general case, then names where the connection is reliable without one: a surface mounted box in direct metal to metal contact with the yoke, a listed device identified for the purpose, and a listed floor box.
• 250.119 identifies equipment grounding conductors as green, green with yellow stripes, or bare, and permits field identification only above a size it states. A 10 AWG spare with green tape on both ends falls below that, so it has to arrive identified.

The thread through all four is that the next person into the box reads color and metal contact, and each rule removes something they'd otherwise take on trust.

Where the letters moved in 2026

NEC 250.122 was restructured for the 2026 edition. Three lettered subdivisions now stand at the front where the 2023 edition had one, so everything behind them shifted down two letters and the section now runs from (A) through (I). Increased in Size moved from (B) to (D), and Conductors in Parallel from (F) to (H). NFPA states the restructure carries no technical change.

Our own practice material shows the drift. Two items in the bank cite 250.122(B) for the proportional increase, which is the 2023 address, while the sibling page on this topic reports the 2026 edition carrying that rule at 250.122(D). Both descriptions agree and the letters differ, which is what a candidate meets when older study material sits beside a current code book.

The safe habit is finding the subdivision by its title. Not Larger Than Circuit Conductors, Increased in Size, Conductors in Parallel, Feeder Taps. Those titles held still while the letters moved around them.

It matters in Texas from a specific date. 16 TAC 73.100 adopts the 2026 edition effective September 1, 2026, and from that day the examinations reference it, which our page on which code edition applies sets out.

What to do before test day

Work every sizing item in this order, because the order keeps you out of both traps.

1. Find the rating of the overcurrent device ahead of the circuit, leaving the load and conductor size alone.
2. Read Table 250.122 at that rating, in the column for the material the stem gives you.
3. Check whether the ungrounded conductors were increased for something beyond ambient correction or conductor-count adjustment, and scale up by the circular mil ratio if so.
4. Apply the cap. The answer stays at or below the circuit conductors in that raceway or cable, and on a parallel run at or below the largest ungrounded conductor there.

Skip step three and you underanswer. Skip step four and you overanswer. Both wrong answers are printed for you on the sheet, which is why running the four steps in order beats recognizing the item type.

Before the day, tab Table 250.122 and write the four steps beside it, because Texas allows notes written in beforehand and bars marking the book during the session. Use tabs the publisher of the code book manufactured or provided. For the code reading and the worked arithmetic, the question sets has the equipment grounding conductor, and the grounding electrode conductor page here covers the other table. Then sit thirty free timed questions.

Questions people ask

What is an equipment grounding conductor sized from?

From the rating of the overcurrent protective device ahead of the circuit, read against Table 250.122. The load, the conductor lying beside it and the service size all sit outside the input. The device rating is what the table is entered on because the conductor has to hold together long enough for that particular device to open. The row then prints separate figures for copper and aluminum, with the aluminum figure larger all the way down the table. Two further rules can change the answer: a proportional increase where the ungrounded conductors were upsized, and a cap at the circuit conductor size.

Can the equipment grounding conductor be larger than the circuit conductors?

It is never required to be. NEC 250.122(A) caps it at the circuit conductors supplying the equipment, and in the 2026 edition that subdivision stands first in the section. The cap exists because the table entered at a large device rating can otherwise hand you a grounding conductor heavier than the conductors feeding the fault, which buys nothing. A separate cap covers parallel runs at 250.122(H), holding the conductor in each raceway at the largest ungrounded conductor in that raceway. An item giving you a small circuit and a large device is testing this rule and nothing else.

When does the equipment grounding conductor have to be increased?

Where the ungrounded conductors are increased for any reason beyond the ambient correction in 310.15(B) or the conductor-count adjustment in 310.15(C). The wire-type grounding conductor then goes up in proportion to the increase in circular mil area. Upsizing the phase conductors for voltage drop carries it along, and upsizing them because the run is hot or crowded leaves it at the table size. Proportional is measured in circular mils, so moving it by the same number of AWG sizes fails the rule. Find the ratio the ungrounded conductors grew by, apply that ratio to the tabulated area, and take the first size at or above the result.

How is it sized in parallel raceways?

On the rating of the single overcurrent device ahead of the whole feeder or branch circuit, with a wire-type conductor in each raceway connected in parallel with the others under NEC 250.122(H). The rating is never divided by the number of raceways, and the fractions that division produces are the wrong answers printed on the sheet. The per-raceway cap then applies, holding each conductor at the largest ungrounded conductor in its own raceway. Where the conductors are paralleled inside one raceway, gutter or cable tray, a single grounding conductor sized on that same device rating is permitted.

Does a circuit always need a green wire for grounding?

Article 100 describes this as a conductive path, so a wire is one way to build it and NEC 250.118 lists the others, raceways and cable armor among them. A circuit run in a recognized metal raceway that stays electrically continuous has a complete equipment grounding conductor with nothing green in it. The flexible types carry extra conditions: a limit on the length of the ground return path, a limit on the device rating ahead of it, and a bar on relying on the conduit where flexibility is needed after installation. A motor whip that moves gets a wire-type conductor pulled through it.

Which subdivision letters changed in the 2026 NEC?

NEC 250.122 gained three lettered subdivisions at the front, so the section now runs from (A) through (I) where the 2023 edition stopped at (G). Increased in Size moved from (B) to (D) and Conductors in Parallel moved from (F) to (H), and NFPA states the restructure carries no technical change. Practice material written against the older edition still cites the old letters, including two items in our own bank that cite 250.122(B) for the proportional increase. Find each subdivision by its title, because the titles held still while the letters moved.