CCT CCT Electrical Systems & Wiring 1 — Questions and Answers
Question 1: What is the purpose of a ground fault circuit interrupter (GFCI) when wiring a Casper system in a US installation?
- To increase voltage to the system
- To protect personnel from electric shock by detecting leakage current to ground (Correct answer)
- To regulate system output frequency
- To prevent overloading the neutral conductor
Correct answer: To protect personnel from electric shock by detecting leakage current to ground
A GFCI detects imbalances between hot and neutral current that indicate leakage to ground and trips within milliseconds to protect personnel from electric shock.
Question 2: According to NFPA 70 (National Electrical Code), what color is the grounding conductor in a standard US branch circuit?
- White
- Black
- Green or bare copper (Correct answer)
- Red
Correct answer: Green or bare copper
The NEC requires the equipment grounding conductor to be green, green with yellow stripe, or bare copper to distinguish it from current-carrying conductors.
Question 3: A Casper system's nameplate states 120 V / 10 A. What is the minimum circuit breaker rating required under NEC continuous-load rules if the equipment runs continuously?
- 10 A
- 12.5 A (125% of 10 A) (Correct answer)
- 15 A based on standard breaker sizing only
- 20 A always
Correct answer: 12.5 A (125% of 10 A)
NEC Section 210.20 requires overcurrent protection rated at least 125% of a continuous load, so 10 A × 1.25 = 12.5 A minimum, typically met with a 15 A breaker.
Question 4: What does the term 'voltage drop' refer to in a Casper system's supply wiring?
- The sudden loss of AC frequency
- The reduction in voltage along a conductor due to its resistance and the current flowing through it (Correct answer)
- The difference between AC and DC voltage
- The output fluctuation caused by load shedding
Correct answer: The reduction in voltage along a conductor due to its resistance and the current flowing through it
Voltage drop is the decrease in electrical potential along a wire caused by the wire's resistance and the current it carries, and excessive drop can impair equipment performance.
Question 5: Which wiring method is commonly used to protect Casper system conductors in industrial or commercial environments requiring mechanical protection?
- Open wiring on insulators
- Electrical metallic tubing (EMT) conduit (Correct answer)
- Flat ribbon cable
- Twisted-pair telephone wire
Correct answer: Electrical metallic tubing (EMT) conduit
EMT conduit provides mechanical protection for conductors in commercial and industrial settings and is one of the most widely used raceway systems under the NEC.
Question 6: Before performing any wiring work on a live Casper electrical panel, what lockout/tagout (LOTO) step must be completed first?
- Attach the tag after completing work
- De-energize the circuit and apply a personal lock to the isolating device before touching any conductors (Correct answer)
- Wear rubber-soled shoes only
- Notify a supervisor after starting work
Correct answer: De-energize the circuit and apply a personal lock to the isolating device before touching any conductors
LOTO requires de-energizing the circuit and applying a personal lock to the energy isolation point before any contact with electrical conductors, per OSHA 1910.147.
CCT CCT Electrical Systems & Wiring 1
What is the purpose of a ground fault circuit interrupter (GFCI) when wiring a Casper system in a US installation?