The goal of electrical exam prep is to be prepared to actually pass the exam. The best way to prepare to pass the exam is to focus on developing three main skills.
- Use key words in questions to locate NFPA 70 code reference answers quickly.
- Become comfortable answering questions that require the use of formulas.
- Lean the test taking and time management skills required.
Let’s see how one or more of these skills can be applied in answering the following exam question:
What size grounding electrode conductor is required at the service supplied by an 3/0 AWG feeder conductor?
The key word or phrase in this question is “Grounding electrode conductor”. Look up this phrase in the NFPA 70 code index, then look for “Sizing” because that’s what you’re trying to accomplish. The index references Article 250.66 which specifies that the size of the grounding electrode conductor at the service shall not be less than given in Table 250.66.
Note that while the question did not indicate whether the conductor wire type is copper or aluminum, NFPA Article 110.5 indicates that “where the conductor material is not specified, the sizes given in the code shall apply to copper conductors.”
Remember that when reading Table 250.66 you must read within the same metal type, copper to copper or aluminum to aluminum. Since we are to assume the metal type used is copper and the question indicates that the service is supplied by a #3/0 AWG service-entrance conductor, the corresponding size of grounding electrode conductor required is #4 AWG copper.
The key to correctly answering this question was identifying the key words that allowed for quickly locating the code article that answered the question.
Learn everything you’ll need to know about how to effectively use this code table and the many others you’ll be required to refer to on the exam. We’ll help you learn what you need to know to pass your electrical exam. Call 888-919-3926 today.