Boxes and conduit bodies on the Texas exam, where the conductor size picks your sizing method before any arithmetic starts

One box, three separate exam items

A single box on a drawing generates three questions, answered from three different places. Is an enclosure needed here at all, and does it have to be a box. Is this one big enough, which is a different calculation depending on what is inside it. Is it accessible, supported and deep enough once it is installed.

Candidates prepare for the middle one, because every study guide covers it and it looks like the hard part. The other two are read-the-sentence questions, cheaper to get right and the better return on a study hour.

On the published PSI content outline, wiring methods and materials carries 10 of the 56 scored items on the journeyman NEC knowledge portion, which runs 130 minutes across 59 items, about 2.2 minutes each. Enclosure rules pay on that half of the paper. In our own bank, 51 of the 500 items sit in the conduit and raceways area, and the four mentioning pull points all sit on the installation side of this topic. Using the code book and exam day covers that weighting.

Where the code wants an enclosure

Article 300 carries the general answer. A box, conduit body or fitting goes at every conductor splice, at every outlet, at every switch point, at every junction, at every termination and at every pull point, unless the code says otherwise. The 2026 book puts that at NEC 300.17, which was 300.15 in the edition before it, so a citation to 300.15 tells you which edition a source was written against.

The exceptions are the tested part. Several wiring methods carry their own permission to make a connection without a box, and some equipment enclosures and listed assemblies serve as the enclosure themselves. An item is usually built by describing an installation with no box in it and asking whether that passes, so the answer sits in an exception.

One exception answers the does-it-have-to-be-a-box half directly. A fitting identified for the use stands in for a box or a conduit body where no conductor is spliced or terminated inside it, and where the fitting serves as a pull point it stays accessible after installation. The sentence people forget beside it is the free conductor length left at every enclosure, measured from where the conductor emerges from its raceway or sheath, which the 2026 book carries at NEC 300.16.

The conductor size fork

The first fork is conductor size and it is sharp. Conductors 6 AWG and smaller stay inside NEC 314.16. Conductors 4 AWG or larger go to NEC 314.28, which is a different method built on geometry. There is no trade size between 6 AWG and 4 AWG, so nothing sits in the gap and there is no judgment call to make.

So the first fact to find in any enclosure stem is the largest conductor in the box. That figure chooses your method before you count anything, and a candidate counting conductor allowances on a 2 AWG pull has already spent minutes on a calculation the section never asked for.

The second fork is taken only on the 6 AWG and smaller branch, and it applies to conduit bodies: whether anything is spliced, tapped or mounted inside. Both forks are clean decisions, which is what makes this topic quick once the order is fixed. The worked arithmetic behind each branch lives on the question set at its boxes and conduit bodies page.

Sizing a conduit body

The heading over the fill rules names boxes and conduit bodies together, and both are sized to give free space to everything inside. A conduit body is an enclosure in its own right, which is why it can answer a pull point question.

With conductors 6 AWG and smaller and nothing spliced inside, a conduit body used purely as a pull point is sized against the raceway. Two comparisons, and both come out of conduit fill: the cross-sectional area of the body against the area of the largest conduit or tubing it can be attached to, with the section stating the multiple, and the conductor count against what Chapter 9, Table 1 allows in that conduit. There is no cubic inch total anywhere in that branch.

Put a splice, a tap or a device inside and a marking becomes the gate. Only a conduit body durably and legibly marked by its manufacturer with its volume may contain one, and once it does, the conductor count comes from the box fill calculation and the six categories apply, with the area comparison underneath as the floor. Where a scenario puts a splice in a conduit body and gives you no marked volume, the marking is the answer the item wants.

What the pull point method measures

NEC 314.28 sizes a pull or junction enclosure from the trade size of the raceway entries, taking no account of what is inside them. The reason is mechanical. A large conductor has a bending radius, and the enclosure exists to give you room to make that bend without damaging the insulation.

The method has two cases and they are measured differently. A straight pull is measured from the wall where the raceway enters to the opposite wall of the enclosure. An angle pull, a U pull or a splice is measured from each raceway entry to the opposite wall, and a further distance is required between two entries carrying the same conductor. Each case is a multiple of the largest raceway trade size, and both multiples are printed in the section.

Two habits pay here. Sketch the enclosure with its raceways before calculating anything, because the case follows from the picture. And read whether the item wants an enclosure dimension or the distance between two entries, since the section gives both and the other is always among the options.

Support, and the line 314.23 draws

A conduit body can be carried by the raceways entering it, and putting a splice inside leaves that permission where it was. This is the most common wrong belief on the topic, including in published study material, so the line is worth placing exactly.

NEC 314.23(E) governs an enclosure holding no device other than splicing devices and supporting no luminaire, lampholder or other equipment. Wire connectors sit on that side of the line. The conditions are a ceiling on enclosure size, threaded entries or hubs identified for the purpose, two or more conduits threaded wrenchtight into the enclosure or its hubs, and each of those secured within a stated distance, shortened where every entry is on one side.

Then comes the exception that decides most conduit body items. A conduit body no larger in trade size than the largest conduit or tubing attached to it can be supported by a single raceway, and the exception names which raceway types qualify, a list the 2026 edition widened. NEC 314.23(F) is the other side: put in a device that does no splicing, or hang a luminaire, and the securing distance tightens and the exception narrows.

Accessible, deep enough and strong enough

Article 314 keeps boxes and conduit bodies reachable after the drywall, the ceiling and the paint. The test is about getting to the wiring inside, and it is written against the building. Where reaching the conductors means removing part of the structure or the finish, the enclosure fails it.

The scenarios write themselves and the exam uses all of them: a junction box sheeted over, or a conduit body behind a permanent architectural panel. Underground enclosures are handled separately, so read what sits under the general rule in your own copy before marking a buried installation as a violation.

Two more requirements catch a correctly sized enclosure. NEC 314.24 sets a minimum depth for outlet and device boxes, keyed to the largest conductor entering and to equipment projecting backward, so a shallow box with a deep device passes on volume and fails on depth. NEC 314.27 governs a box carrying a luminaire or a ceiling-suspended paddle fan, and it marks some cases by what the box is listed for. One exclusion sits above all of it: the fill rules leave motor and generator terminal housings alone.

Where the wrong answers come from

Every item in our bank names the mistake behind each wrong option. On this topic they cluster in a way that is easy to guard against.

Each of those is settled before arithmetic starts. Read the largest conductor, read what is mounted inside, then pick the method.

What to do before test day

The Texas exam is open book and you carry your own copy, so the work now is in the book:

• Write the conductor size fork on the first page of Article 314 in your own words, with 314.28 beside the 4 AWG figure.
• Tab 314.23(E) and (F) together and mark the word device in both, since that word decides which one you are in.
• Where your notes cite 300.15 or 300.14, write the 2026 numbers beside them, which are 300.17 and 300.16.
• Practice sketching a pull enclosure with its raceways before reading the options.

Texas adopts the 2026 National Electrical Code on 1 September 2026 under 16 TAC 73.100, and both subsections of 314.23 were revised for that edition, so this topic wants a current book. Which code edition applies to you covers the licensing side of that date, and city amendments sit on top of the state adoption under Tex. Occ. Code 1305.201(c) and (d), which what a city can still require of you sets out. The thirty free timed questions at practice will show you whether the fork is automatic yet, and conduit bending math covers the pull point from the degrees side.

Questions people ask

Can a conduit body be supported by the raceway if there is a splice in it?

Yes. NEC 314.23(E) turns on what is mounted in the enclosure, and splicing devices such as wire connectors sit on the permissive side of that line. Its exception lets a conduit body no larger in trade size than the largest conduit or tubing attached to it be supported by a single raceway, and the 2026 edition widened the list of raceway types that qualify. What a splice does change is the fill section, since it brings the volume marking and the box fill count with it. Put in a device that does no splicing, or hang a luminaire, and NEC 314.23(F) takes over.

Which method sizes a conduit body?

Start with the largest conductor. At 4 AWG or larger, NEC 314.28 governs and the sizing comes from raceway trade sizes and geometry. At 6 AWG and smaller with nothing spliced, tapped or mounted inside, the body is sized against the raceway: its cross-sectional area against the area of the largest conduit it can attach to, and the conductor count against what Chapter 9 Table 1 allows in that conduit. At 6 AWG and smaller with something inside, the marked volume gates it and box fill applies on top of the area comparison.

Do you need a marked volume to splice in a conduit body?

Yes. Only a conduit body durably and legibly marked by its manufacturer with its volume is permitted to contain a splice, a tap or a device. Once it contains one, the conductor count comes from the box fill calculation and the raceway area comparison stays underneath as a floor. Where a scenario describes a splice in a conduit body and says nothing about a marking, the marking is what the item is fishing for. A short radius body such as a capped elbow or service entrance elbow gets no splice at all, whatever it is marked with.

What does a pull point do to the bend count?

It restarts it. The limit on degrees of bend is written for the run between pull points, so a box or a conduit body used as a pull point ends one run and begins the next, and the count starts again from zero on the far side. The conduit body adds no degrees of its own, since any bend formed inside it belongs to the run it sits in. What a pull point leaves alone is the fill, because the same conductors continue on both sides and both areas in the comparison are unchanged.

What is NEC 314.28 actually measuring?

Room to bend a large conductor without damaging its insulation, which is why the method reads trade sizes and takes no account of what is inside the raceways. A straight pull is measured from the wall where the raceway enters to the opposite wall. An angle pull, a U pull or a splice is measured from each entry to the opposite wall, and a further distance is required between two entries carrying the same conductor. Each case is a multiple of the largest raceway trade size, the multiples differ, and both are printed in the section.

Was 300.15 renumbered in the 2026 code?

It is 300.17 in the 2026 edition, and it carries the same job: a box, conduit body or fitting at every splice, outlet, switch point, junction, termination and pull point unless the code says otherwise. The companion rule on minimum free conductor length moved from 300.14 to 300.16, and the box fill rules point at it by number when they explain the loop that counts twice. A source still citing 300.15 or 300.14 was written against the 2023 book, which is worth knowing before you trust the rest of it.