Texas Electrician ExamTexas journeyman & master

Checked against primary sources 2026-08-24

An enclosure type is a statement about the environment, not a grade

Everybody has a default enclosure they reach for on site. Items on this subject are written for the person who answers from that default.

On this page
  1. What the number is actually telling you
  2. Two documents, two jobs
  3. How to enter the table
  4. What decides which one you need
  5. What can spoil an enclosure after you have chosen it
  6. Why this is worth twenty minutes
  7. What this page cites

What the number is actually telling you

An enclosure type designation is a claim about conditions. It says this box has been tested to keep out a particular set of things, in a particular way, and it says nothing at all about how thick the metal is or how well made it is.

Read as a list of conditions, the whole subject becomes easy. Read as a quality scale, it stays confusing forever, because the numbers do not behave like a scale.

So the first move on any item of this kind is to stop looking at the type numbers in the options and start looking at the words in the stem describing where the equipment is going.

Two documents, two jobs

The code does not define the type numbers. They come from a product standard, ANSI/NEMA 250, titled Enclosures for Electrical Equipment (1000 Volts Maximum), which is where the design tests live. Its scope covers enclosures rated at not more than 1000 volts and sorts them by where they are intended to be used, in three groups: indoor only, indoor or outdoor, and hazardous locations.

The code does two different things with those numbers. Enclosures of the equipment the section lists must be marked with an enclosure-type number as shown in Table 110.28 (NEC 110.28), and the table itself, titled Enclosure Selection, is how you get from a location to the types that answer it. So the standard says what a type is and how it was tested. The code says which ones belong where, and requires the marking that lets you tell.

The design tests behind those types are physical and they are worth knowing as a set, because they are the vocabulary the table is written in. Protection against access to hazardous parts and against solid foreign objects. Water arriving as drips, as light splashing, as rain, as a hosedown, or as submersion, temporary or prolonged. Dust, windblown and indoor. Oil. Corrosion, tested with salt spray and with moist carbon dioxide. Each type is a particular subset of that list.

Once you have seen the test list, the odd behavior of the numbering stops being odd. A type built to shed falling rain was never asked to keep out windblown dust, so it does not, and no amount of the number being larger changes that.

There is one sentence in 110.28 that is worth more on the job than anything else in it. The enclosures are not intended to protect against condensation, icing, corrosion or contamination that occurs inside the enclosure, or that gets in through the raceway or through unsealed openings. Picking the right type does nothing about water that arrives up the conduit, and an item describing an underground run into an outdoor enclosure may well be asking about that rather than about the type number.

How to enter the table

The table is indexed by condition, not by type. That single fact is most of the technique.

  1. Read the stem and write down the location in the code’s own words, not in yours. Indoors or outdoors first, because the standard and the table both split there before anything else.
  2. Turn the description into the specific conditions the table is written in. Rain is one thing, hosedown is another, and airborne dust is a third.
  3. Find those conditions in the table and read across to the types that answer them.
  4. Compare that set with the options. If two options both appear, the item is testing a second condition you have not spotted yet, so go back to the stem.

That is a lookup rather than a recall problem, which is exactly what an open book examination is for. The candidates who lose these items are the ones who never open the book, because they already know what enclosure they would have used.

What decides which one you need

The location, and the location is a defined term rather than a description. Dry location, damp location and wet location are all defined in Article 100, and a stem that carefully mentions a canopy, a soffit or a below-grade raceway is describing a definition rather than setting a scene.

That is where most of the marks are. An enclosure item and a wet location definition item are frequently the same item wearing a different coat, and a candidate who reads the Article 100 definitions once has answered both.

The second decider is the listing. Equipment is used the way it was listed to be used, and the type marking is part of that listing. An enclosure listed for one set of conditions does not become suitable for another because it was installed carefully.

What can spoil an enclosure after you have chosen it

Choosing the right type and then defeating it is a real failure mode on the job, and the rules that stop it are scattered between the code and the product standard rather than gathered in one place.

Article 314 adds more for boxes and conduit bodies, including provisions specific to damp and wet locations, and it is a separate read from Article 110.

Why this is worth twenty minutes

Enclosure selection sits inside the joint largest subject area on the journeyman knowledge portion, and it is one of the few subjects where the correct method is a single table lookup that almost nobody performs.

It is also one of the few where field experience actively hurts. An electrician who has installed the same enclosure on four hundred outdoor jobs has a strong, fast, confident answer available, and the item exists because that answer is right most of the time and not all of the time.

Find the table in your own book tonight, read the column headings, and put a tab on it. You are not learning the pairings. You are making sure that under a clock your hand knows where they are.

What this page cites

NEC and National Electrical Code are registered trademarks of the National Fire Protection Association.

Trojan Digital Marketing is an independent company. We are not affiliated with, endorsed by, or sponsored by NFPA, TDLR, PSI Services, or any licensing authority.

Bring your own current copy of the National Electrical Code. The Texas exam is open book.

All practice questions are original. They are not actual exam questions.

Built and maintained by Jeff Clerisier, Trojan Digital Marketing.

Every rule here is cited to the section it comes from, and corrections are logged in public with the date. This is study material rather than electrical advice, and it does not replace your own code book or your inspector.