Most-missed NEC mock exam question #3 of 5, from JCR's free 25-question NEC mock exam. On a breaker, SWD means "switching duty" and HID means "high-intensity discharge." 67% of students got this wrong. Try it with your 2020 NEC open, then check your answer below.
Show the answerHide the answer
The answer: B, two only
240.83(D) requires a breaker used as a switch in a 120-volt or 277-volt fluorescent lighting circuit to be listed and marked SWD or HID. The rule says nothing about being approved for continuous duty. So statement 1 is not a requirement.
Why so many people pick "both"
"Both one and two" was the top wrong answer, picked by 43% of students. Statement 1 sounds reasonable, since lighting runs for hours.
But 240.83(D) asks for only two things: the breaker is listed, and it is marked SWD or HID. On "one only / two only" questions, check each statement against the code text by itself.
Want hundreds more questions like this one? JCR's $495 self-study package has 500+ practice questions (digital and printed), 100 video lessons, a 152-page study manual and permanent code tabs. Videos and the digital practice exams open right after you order.
Testing in North Carolina? Take JCR's NC exam prep class: two full days in person ($845) in Raleigh, Asheville, Mooresville (Charlotte area) or Winston-Salem, or live on Zoom on Tuesday evenings and Saturday mornings. 93% pass rate for JCR classroom students.
What 240.83(D) says
- Fluorescent lighting circuits, 120 V and 277 V: a breaker used as a switch must be listed and marked SWD or HID.
- High-intensity discharge (HID) lighting circuits: a breaker used as a switch must be listed and marked HID.
So an HID marking covers switching either kind of circuit. An SWD marking alone is not enough for an HID lighting circuit.
The other breaker markings in 240.83
- (A) Ampere rating, durable and visible after installation. It may be made visible by removing a trim or cover.
- (B) Breakers rated 100 A or less and 1000 V or less: ampere rating molded, stamped, etched or similarly marked into the handle or escutcheon area.
- (C) Interrupting rating shown on the breaker if it is other than 5000 A. Not required on breakers used for supplementary protection.
- (E) Voltage rating not less than the nominal system voltage.
Common questions
Can I use a breaker as a light switch?
Yes. 404.11 lets a hand-operable breaker serve as a switch if it has the required number of poles. On 120-volt and 277-volt fluorescent lighting circuits, it must also be listed and marked SWD or HID (240.83(D)). On HID lighting circuits, it must be listed and marked HID.
What does SWD mean on a breaker?
SWD stands for "switching duty." It shows the breaker is listed for regular on-off switching of fluorescent lighting loads.
Is an HID breaker OK on a fluorescent circuit?
Yes. 240.83(D) accepts SWD or HID for fluorescent lighting, so an HID-marked breaker covers both. An SWD-only breaker can't be used to switch HID lighting.
This explanation follows the 2020 NEC. Buy a printed copy here or read it online with a paid NFPA LiNK subscription. Look up the edition your state tests.
JCR checked this against the 2020 NEC in NFPA LiNK on October 21, 2026.
Related guides: How to size a motor breaker (Table 430.52) · 100%-rated breakers and continuous loads · The 5 most-missed NEC mock exam questions
The 5 most-missed NEC mock exam questions
- Pull box size for an angle pull (314.28)
- Continuous loads on a 100%-rated assembly (210.20(A))
- Breakers used as switches: SWD and HID (240.83(D)) (this post)
- Motor overload sizing and service factor (430.32)
- Closet light clearance (410.16(C))
See all 5 most-missed questions on one page.
More free lessons on the JCR YouTube channel
Know where to look, fast
Most electrical exams let you use the NEC. The skill is finding the right section quickly, and that's what JCR's self-study package trains.
Self-study package: $495
- 152-page JCR study manual with a six-week study plan
- 100 video lessons (21 hours) that follow the manual
- Realistic 500+ question mock exam (digital access and on paper)
- Permanent code book tabs
Videos and the digital mock exam arrive by email right after you order. Printed materials ship the same business day.
Prefer a classroom? Exam prep workshops: two full days in Raleigh, Asheville, Mooresville (Charlotte area), Winston-Salem, or live on Zoom. Includes all materials (mock exam, videos, study manual) except for NFPA 70 and 72 books. 93% pass rate for JCR classroom students.
Choose your state's self-study package
Each package is built for that state's exam and NEC edition. Pick yours:
Not sure which exam you need? See your state's license and exam requirements.
More worked examples: all NEC Answers.
Already licensed? CE classes: 8 hours, in person or on Zoom, approved in 20+ states.