ICC G21 Low-Voltage Electrician (2017 NEC) Exam: A Practical Study Guide
The ICC G21 Low-Voltage Electrician (2017 NEC) exam tests the rules and the reference books behind the work. This guide lays out the job: the key facts from the official bulletin, what the exam covers, the books you need, sample questions with answers, and how to get ready. Pearson VUE gives the exam.
The ICC G21 Low-Voltage Electrician (2017 NEC) Exam at a Glance
Here's the rundown from the official bulletin:
| Questions | 50 questions |
| Time limit | 3 hours |
| Passing score | 70% correct |
| Books in the exam room | Open book |
| Exam fee | $120 |
On exam day
- Questions are four-option multiple choice with one correct answer.
- You may bring copyrighted, bound books to the test administration, including those specifically listed as approved references. However, training materials such as presentations, study guides, or practice questions are not permitted. All exam questions are based solely on the approved reference list, and only those references may be used as the basis for appealing exam questions.
References you may bring
- National Electrical Code (NEC) (2017)
- Ugly's Electrical Reference (any edition)
Scheduling, changes and retakes
- Exams are scheduled through PearsonVUE at www.pearsonvue.com/ICC, where candidates can create an account, schedule an exam, locate a test center, purchase vouchers and request accommodations.
- Results for examinations taken electronically are available immediately after the examination is completed.
- You must wait 10 days before retaking a failed exam.
- After passing, contact the jurisdiction in which you wish to be licensed for any other requirements, because ICC is not a licensing agency.
Source: National Contractor/Trades Examination Information Bulletin, PUBLISHED June 30, 2026; ICC Exam Catalog, checked September 27, 2026. Check the bulletin before test day: fees and rules can change.
What the ICC G21 Low-Voltage Electrician (2017 NEC) Exam Covers
The official content outline breaks the exam into 5 topics:
| Topic | Questions | Share of the exam |
|---|---|---|
| General Knowledge | 12 | 24% |
| LV Remote Control & Alarm Systems | 11 | 22% |
| LV Communications & Sound | 18 | 36% |
| LV Control Circuits | 7 | 14% |
| Fiber Optical | 2 | 4% |
How to Get Ready for the ICC G21 Low-Voltage Electrician (2017 NEC) Exam
Treat your reference books like your tools. On an open-book exam you don't need every rule memorized. You need to know which book holds it and where to find it.
Buy the books the bulletin lists, in the editions it names. An older or newer edition can put the answer on a different page, or change it.
Learn your way around each book before you study anything else. The table of contents and the index are your layout.
Highlight what you look up most. The exam facts above list the bulletin's rules on tabs and markings, so follow them exactly.
Do the big jobs first. LV Communications & Sound and General Knowledge make up 60% of the exam.
Put in the reps with timed practice exams. The clock trains you to find answers at the pace the real exam needs: about 3 minutes 36 seconds per question.
Measure twice. When you miss a practice question, find the section in your book, read it and mark it. Keep at it until you pass practice exams consistently.
The Books for the ICC G21 Low-Voltage Electrician (2017 NEC) Exam
The listed references are the 2017 National Electrical Code (NEC) and Ugly's Electrical Reference (any edition).
Where to get them:
Working the Exam on Test Day
Work the exam in two passes. On the first pass, answer everything you know and bookmark the rest. Every exam lets you come back to bookmarked questions. On the second pass, go back to your bookmarks and take them one at a time.
Don't get hung up on one question. You have 3 hours for 50 questions, which is about 3 minutes 36 seconds per question. Before you finish, make sure nothing is left blank.
Study Tips
On an open-book exam, the winners aren't the smartest people in the room — they're the fastest at finding answers. Buy the required book, practice with it open, and tab and highlight each section the first time a question sends you there. Learn the index and table of contents until you can land on any topic in seconds. That speed is what separates a pass from a fail.
Know your way around each book's index and table of contents. Open-book exams reward speed: you need to find specific items quickly.
On an open-book exam, work through every question once: answer the ones you know and skip the ones you don't. Then go back to the ones you flagged. You can bookmark questions for later review, just like on our exams — and don't sink too much time into any single question. The clock is still running.
Give yourself at least three to six weeks. Use your exam's candidate bulletin as your roadmap for what's tested, and spend your time on finding-it-fast skills over rote memorization. In practice, aim for three clean passes at 80% or higher — setting your practice bar above the real cut score gives you a comfortable margin on test day.
Practicing against a ticking clock is the best way to beat exam-clock anxiety. Use these timed tests to build your pacing, so you learn to move steadily and never burn too long on a single question. By test day, the format feels routine.
This practice exam mirrors the real Pearson VUE exam — the same number of questions, drawn from the same topics. Practicing in that format now means no surprises when you sit for the real thing.
Sample ICC G21 Low-Voltage Electrician (2017 NEC) Questions
These come from our practice question bank, each with its answer and the reference behind it.
Sample 1 — LV Control Circuits
Question: Where one conductor of a motor control circuit is grounded, the circuit must be arranged so that a ground fault in the control circuit remote from the motor controller will not start the motor and will not do which of the following?
- A. De-energize the reduced-voltage control transformer
- B. Bypass manually operated or automatic shutdown devices
- C. Energize the motor overload relay heater elements
- D. Open the motor branch-circuit protective device
Correct Answer: B
NEC 430.74 states that where one conductor of the motor control circuit is grounded, the circuit shall be arranged so that a ground fault remote from the controller will (1) not start the motor and (2) not bypass manually operated shutdown devices or automatic safety shutdown devices.
Reference: NEC 2017 Section 430.74
Sample 2 — Fiber Optical
Question: In other spaces used for environmental air (plenums), which optical fiber cable types are permitted to be supported by open metallic cable trays?
- A. Types OFNR and OFCR only
- B. Types OFNG and OFCG only
- C. Types OFN and OFC only
- D. Types OFNP and OFCP only
Correct Answer: D
NEC 770.113(C)(4) and Table 770.154(a) permit only Types OFNP and OFCP to be supported by open metal cable trays in other spaces used for environmental air. Lower-rated types are permitted there only in compliant metal raceway or in solid bottom metal trays with solid metal covers.
Reference: NEC 2017 Section 770.113(C) and Table 770.154(a)
Sample 3 — LV Communications & Sound
Question: You are installing Type CMX communications cable in an office building corridor — a nonconcealed general building location that is not a duct, plenum, riser, cable tray, or distributing frame. The run must be 40 ft long, well beyond the length permitted for exposed CMX in such locations. Which installation method makes the 40 ft run permissible?
- A. Install the CMX in a riser cable routing assembly
- B. Install the CMX in electrical metallic tubing
- C. Support the CMX on a solid-bottom metal cable tray
- D. Install the CMX in a general-purpose communications raceway
Correct Answer: B
NEC 800.113(J) permits only a maximum of 10 ft of exposed Type CMX in nonconcealed spaces in other building locations, but 800.113(J)(7) permits Types CMP, CMR, CMG, CM, and CMX to be installed in raceways of a type recognized in Chapter 3 (such as EMT) without that length limitation. The permitted installations of CMX in communications raceways and cable routing assemblies listed in 800.113(J)(5) and (J)(6) are limited to Types CMP, CMR, CMG, and CM — CMX is not included — and cable tray support under 800.113(H) is likewise limited to Types CMP, CMR, CMG, and CM.
Reference: NEC 2017 Section 800.113(J)(7)
Sample 4 — General Knowledge
Question: When ungrounded supply conductors are larger than 1,100 kcmil copper or 1,750 kcmil aluminum, the grounded conductor or bonding jumper shall have an area not less than _ percent of the area of the largest ungrounded supply conductor.
- A. 10
- B. 12.5
- C. 15
- D. 20
Correct Answer: B
Per NEC Table 250.102(C)(1) (reproduced in the reference material), Note 1 states: 'If the ungrounded supply conductors are larger than 1100 kcmil copper or 1750 kcmil aluminum, the grounded conductor or bonding jumper shall have an area not less than 12½ percent of the area of the largest ungrounded supply conductor or equivalent area for parallel supply conductors.'
Reference: NEC 2017 Section 250.102(C)
Why Practice Online Instead of With a PDF
A PDF is like reading about a job instead of doing it. Our practice exams are timed and on a screen, so you practice finding answers with the clock running. Each attempt draws a new set of questions from our bank, and your results break your score down by topic so you know where to put in more work.
Get Started
Take the free ICC G21 Low-Voltage Electrician (2017 NEC) practice exam to see where you stand, then put your time into the topics that need it. For the official rules, read the exam bulletin, and see the licensing board's website.