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Practice question · NEC Table 300.5
How Deep Do You Bury a GFCI-Protected Residential Branch Circuit?
How deep you bury a GFCI-protected residential branch circuit is a column question, not a depth question. Table 300.5 prints several depths side by side, and the stem gives you every word you need to pick the right column. Pick the general column and you bury it twice as deep as the Code requires.
Exam-style question (Sparky QOTD)
Table 300.5: what is the minimum cover for a direct-buried GFCI-protected 120V, 20A residential branch circuit?
A. 24 in.
B. 18 in.
C. 12 in.
D. 6 in.
Answer: C) 12 in. The "Residential Branch Circuits Rated 120 Volts or Less with GFCI Protection" column in Table 300.5 reads 12 inches.
Where to Find It
Open your Code book to Table 300.5 in Article 300. Do not read down a column yet. Read across the column headings first. One heading matches this stem word for word: "Residential Branch Circuits Rated 120 Volts or Less with GFCI Protection." That column gives you 12 in. of minimum cover. Tab it in your book this way: Article 300, Table 300.5 — the GFCI residential column is the 12-in. shortcut.
Why 12 Inches
Every qualifier in the stem is doing work. Direct-buried puts you in Table 300.5. Residential, branch circuit, 120V, and GFCI-protected are the four words that walk you out of the general column and into the special residential GFCI column. Miss one of those words and you land somewhere else in the table.
The comparison the Code sets up is direct: general direct burial is 24 in., and the GFCI-protected residential branch circuit column is 12 in. — half the depth. That is why option A, 24 in., is on the page. It is the correct answer to a different question: the same circuit without the residential GFCI column applying. We drill that general-column read in the UF cable burial question, where 24 inches is the answer.
Options B and D, 18 in. and 6 in., are there to catch a column or row slip. Table 300.5 rewards one skill: slow down at the headings, match the stem to the column, then read the number. The number itself is the easy part.
The Trap
The trap is answering from habit. Twenty-four inches is the burial depth most electricians carry in their head, so it feels right before you ever open the book. The exam knows that. When a stem loads up qualifiers — residential, 120 volts or less, GFCI protection — it is telling you a special column exists. Qualifiers are never decoration.
Exam Tip
On any Table 300.5 question, underline the qualifiers in the stem, then find the column heading that contains those same words before you look at a single depth. If the words "GFCI" and "residential" are both in the stem, you are in the 12-in. column. Answer and move on.
Keep Drilling
This is one of 33 NEC topics. Sparky's 1,087 codebook-first questions drill all of them — every question a lookup rep with your book open, 15 minutes a day.