Cable Types Practice Questions

C. Wet

The wet location definition is a list of four situations and this is one of them, alongside being unprotected and exposed to weather, being subject to saturation, and being underground. Nothing about the slab has to feel wet for the classification to attach. Classifying the location first is what decides which cable article paragraph you are allowed to open.

NEC 2026 Article 100

A. Damp

Damp is the middle category and it is defined by two conditions holding at once, protection from weather and moderate moisture short of saturation. The informational note under it names partially protected spots under canopies, marquees and roofed open porches. A dry location is one not normally subject to dampness, and a location under construction that gets briefly wet stays dry by that definition.

NEC 2026 Article 100

D. Wet

Article 300 settles this directly by saying the interior of enclosures or raceways installed underground is a wet location, and it sends you to the conductor insulation rule from there. So the conductors pulled into it need insulation listed for wet locations even though the pipe looks sealed on the day it is installed. Groundwater finds the joints eventually, which is the reason for the rule.

NEC 2026 300.7(B)

B. A one-family dwelling and its detached garage

The first entry on the permitted list names one- and two-family dwellings with their attached or detached garages and their storage buildings, and it stops there without asking what the building is made of. Every other entry on that list carries a construction type condition or a raceway condition. Reading only the room and never the building is the standard way to lose one of these.

NEC 2026 334.10

A. The cable is installed within walls, floors or ceilings that provide a thermal barrier of material with at least a 15-minute finish rating

Being permitted in a building is not the same as being permitted anywhere in that building, and this paragraph is where the difference shows. The finish rating condition is the whole point of the entry, since the barrier is what buys the time the construction type assumed. Nothing in the paragraph touches conductor size or circuit rating.

NEC 2026 334.10

C. A nonhabitable grade level storage garage or storage building under 1,500 square feet built to Type V construction

The exception is narrow and it stacks four conditions, nonhabitable, at grade level, under the stated floor area, and Type V construction. Drop any one of them and the barrier condition comes back. An option that names only the construction type is quoting a quarter of the sentence, which is exactly how these distractors are built.

NEC 2026 334.10

B. They are permitted to be of Type III, IV or V construction

The multifamily entry hands you a construction type test, which is a different vocabulary from anything about moisture and a different one again from the story count people remember from older editions. Story count is a building code idea that reached the NEC through the construction type rather than directly. One- and two-family dwellings are the entry with no such condition.

NEC 2026 334.10

D. Not permitted, since wet and damp locations sit on the list of uses not permitted for Type NM

The subsection that applies only to Type NM bars it from wet or damp locations outright, with no condition that buys the use back. Type NMC is the version written for dry, wet, damp or corrosive locations, so an item that names one type rather than the other is asking you to notice which one. The distractors all describe good practice that does not change the answer.

NEC 2026 334.12

A. Buildings other than one- and two-family dwellings and multifamily dwellings

The entry is bounded by occupancy rather than by the ceiling, and the two dwelling categories are carved out of it. So the same installation is a violation in a small office and permitted in an apartment building. A summary that prints the prohibition without the qualifier turns a bounded rule into a blanket one, which is how the second option gets written.

NEC 2026 334.12

C. Commercial garages that have hazardous classified locations as the commercial garage article defines them

The entry is not about commercial garages as a category. It points at the article covering them for the classification, so the prohibition is only as wide as the classified space that article produces. That means the answer to a garage question can turn on where in the garage the cable runs and how the space is ventilated, neither of which is in Article 334.

NEC 2026 334.12, 511.5

D. No, the list of uses not permitted bars it

This entry is written against the job the cable is doing rather than against the room it is in, which is a shape worth recognizing because several prohibitions work that way. Length, conductor rating and occupancy do not enter into it. The cable built for that job is Type SE, and it has its own article with its own pair of lists.

NEC 2026 334.12

B. Type UF

Underground use including direct burial opens the permitted list for Type UF, and the sheath section backs it with a covering that has to be moisture, fungus and corrosion resistant and suitable for burial. Type NM is barred from direct burial by name, and Type SE is barred from underground use with or without a raceway. Type AC is not a burial cable at all.

NEC 2026 340.10, 334.12, 338.12

C. Ampacity adjustment and correction, so long as the final calculated figure does not exceed the 60 degree C ampacity

The ampacity section states the 60 degree ceiling and then hands back the higher rating for the arithmetic in the middle, which is the same shape the termination rule uses. So a hot attic or a crowded bundle is worked from the 90 degree figure and the answer is then held against the 60 degree value. Reading only the first sentence throws away the allowance and oversizes the cable.

NEC 2026 334.80

A. It gives the ampacity as that of 60 degree C conductors and carries no sentence letting a higher rating be used for adjustment and correction

The two sections reach the same ceiling by different routes and only one of them prints the permission to work the middle of the calculation at a higher rating. That difference is invisible if you have learned the pair as one rule. When an item hands you a cable type and an ambient, the first move is to open the ampacity section of that cable's own article rather than the one you read last.

NEC 2026 340.80, 334.80

B. The ampacity of each conductor is adjusted using the conductor count adjustment table

The 2026 ampacity section spells out two bundling cases for these cables, one for cables through the same sealed opening in wood framing and one for cables in contact with thermal insulation, and both send you to the adjustment table. It also switches off the short length exception that would otherwise excuse the run. Insulation is the trigger because it stops the heat leaving.

NEC 2026 334.80, Table 310.15(C)(1)

D. The cable ties, staples, straps and hangers that hold it up

Nonmetallic-sheathed, metal-clad and underground feeder cable all carry a listing requirements section naming the cable and the supporting hardware, and the metal-clad and underground feeder ones add the fittings. It reads like a detail until an item describes the fastener rather than the spacing. An installation can be at the right intervals in a permitted building and still be wrong on the staple.

NEC 2026 334.2, 330.2, 340.2

C. Not permitted, since damp and wet locations sit on the list of uses not permitted

The permitted list for Type AC names dry locations, and the not permitted list closes the door on damp and wet ones from the other direction. The two lists are one rule read forwards and backwards, which is the pattern in every one of these articles. Metal-clad cable is the type with a wet location path, and pairing the two cables is the most reliable distractor set in this subject.

NEC 2026 320.12, 320.10

A. Where those walls are not exposed or subject to excessive moisture or dampness

The same air void appears on both lists with the moisture condition flipped, so the permitted entry and the prohibited entry describe one wall in two states. Support intervals are a separate section and do not decide whether the use is allowed. This is the clean example of why reading only one of the two lists produces a confident wrong answer.

NEC 2026 320.10, 320.12

B. A jacket over the metallic covering, together with one of three stated moisture conditions being met

The wet location entry is a two part test. There has to be a jacket over the metal covering, and then one of three things has to be true about moisture, either the covering itself is impervious, or there is a moisture impervious jacket under the metal, or the conductors inside are listed for wet locations. An exception releases copper alloy armor that is impervious to moisture from the jacket requirement.

NEC 2026 330.10

D. Where subject to physical damage

The uses not permitted section for this cable is short. Physical damage is one entry and destructive corrosive conditions are the other, and the corrosive entry lets the use back in where the sheath resists the condition or is protected against it. The three wrong options are all on the permitted list, which is why a candidate who reads only the prohibition list can still miss this.

NEC 2026 330.12, 330.10

C. In the list of permitted equipment grounding conductor types in the grounding article

The grounding article carries the list of what may serve as an equipment grounding conductor, and it names armored cable armor by reference to that cable's own construction section and gives metal-clad cable three separate ways to qualify. So the answer sits in Article 250 even though the question sounds like a cable question. Two cables that look identical on a rack can land on opposite sides of that list.

NEC 2026 250.118, 320.108

A. Not permitted, since the not permitted list bars Type SE underground with or without a raceway

The entry closes both routes in one clause, which is the detail people miss because a conduit feels like it should solve the problem. The underground member of this family is Type USE, and the two styles are not interchangeable in either direction. Cover depth and conduit material are answers to a different question entirely.

NEC 2026 338.12(A)

D. Not permitted, since interior wiring is the first entry on the list of uses not permitted for Type USE

The two styles in this article are a matched pair of prohibitions. Type SE is barred from going underground and Type USE is barred from interior wiring, so neither one covers the whole run on its own. There is a narrow allowance for Type USE emerging from the ground and terminating in an outdoor enclosure with protection, which is not interior wiring.

NEC 2026 338.12(B)

B. Article 334 Part II, leaving out the ampacity section of that article

For interior work this cable borrows the installation part of the nonmetallic-sheathed cable article and names one section it does not take, the ampacity section. Its own subsection then writes the ampacity rules it does use, including a 60 degree treatment for 10 AWG and smaller ungrounded conductors in contact with thermal insulation. Borrowing a whole part of another article with one section carved out is a shape worth recognizing.

NEC 2026 338.10(B)

C. That the cable be identified as sunlight resistant, since exposure to the direct rays of the sun is otherwise on the list of uses not permitted

Sunlight is one of eleven entries on the not permitted list, and the marking is what buys the use back. An informational note adds that the jacket marking does not carry down to the individual conductors, so a cable opened up and run as single conductors is a different question. Being a burial cable does not make it a sunlight cable.

NEC 2026 340.12