Practice question · NEC 250.104(C)

What Table Sizes a Bonding Jumper for Structural Steel?

By Mason Garry, Master Electrician · October 8, 2026 · 2 min read

Four tables in the options, one correct answer — this is a pure "match the noun" question. The stem says "bonding jumper" and "structural metal." That pairing points to exactly one spot in the Code.

Answer: B) Table 250.102(C)(1). 250.104(C) sizes the bonding jumper for structural metal off the largest ungrounded service conductor.

Where to Find It

Open your Code book to Article 250 and find 250.104(C). It tells you the bonding jumper for structural metal is sized per Table 250.102(C)(1) — based on the largest ungrounded service conductor. Tab 250.104(C) in your book with the note "steel bonds like a service."

Why This Works

The key is the table the Code points you to. Table 250.102(C)(1) is keyed to the largest ungrounded service conductor — bigger service, bigger bonding jumper. The steel frame is bonded like a service conductor, not like a branch circuit, which is why the sizing follows the service size instead of anything about the steel itself.

Match the noun in the stem: the question says "bonding jumper," and the bonding-jumper table for structural steel is Table 250.102(C)(1). The exam loads the options with the other famous grounding tables on purpose — but the noun is your compass. When the stem says bonding jumper, 250.102(C)(1) is where you land.

For more on how these grounding questions show up, browse the study guides — grounding and bonding is one of the most-tested areas on the exam.

The Trap

Option D — "the size of the steel members" — is the trap. It sounds like common sense: big steel, big jumper. But nothing in the Code sizes a jumper off structural member dimensions. The table key is the largest ungrounded service conductor, period. The exam is checking whether you look it up or guess from intuition. Guessers pick D. You look it up and pick B.

Exam Tip

Whenever you see "bonding jumper" in the stem, go straight to 250.102(C)(1) and its parent section 250.104(C). And read what the stem actually names — structural metal, water pipe, gas piping — each has its own section, but they all funnel through the same "match the noun" habit. Tab it once, and these are ten-second questions.

Keep Drilling

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