InterNACHI Electrical Systems and Safety 3 — Questions and Answers
Question 1: What amperage rating is typically required for a dedicated 240V circuit serving a modern electric clothes dryer?
- 15 amps
- 20 amps
- 30 amps (Correct answer)
- 50 amps
Correct answer: 30 amps
Electric clothes dryers require a dedicated 30-amp, 240V circuit with a 4-wire connection per current NEC standards.
Question 2: An inspector observes a junction box in a basement ceiling that has no cover plate. What is the correct finding?
- Acceptable if the box is metal
- A deficiency — all junction boxes must have accessible cover plates (Correct answer)
- Acceptable if wires are capped with wire nuts
- Only required in finished areas
Correct answer: A deficiency — all junction boxes must have accessible cover plates
All junction boxes must have a cover plate installed to contain arcing or sparks and provide access for future maintenance.
Question 3: Which of the following conditions would indicate reverse polarity at a 120V receptacle?
- The hot and neutral wires are connected to the wrong terminals (Correct answer)
- The ground wire is missing
- The outlet is wired with a 20-amp breaker on a 15-amp circuit
- Two outlets share the same circuit
Correct answer: The hot and neutral wires are connected to the wrong terminals
Reverse polarity occurs when the hot wire is connected to the neutral (wide) slot and the neutral to the hot (narrow) slot, creating a shock hazard.
Question 4: In a residential electrical system, what is the purpose of an anti-oxidant compound applied to aluminum wiring connections?
- To increase electrical conductivity above copper
- To prevent oxidation that increases resistance at connections (Correct answer)
- To bond aluminum to copper at splices
- To color-code aluminum wire terminations
Correct answer: To prevent oxidation that increases resistance at connections
Anti-oxidant compound prevents the formation of aluminum oxide at connections, which increases resistance and creates heat buildup.
Question 5: What minimum wire gauge is required for a 20-amp branch circuit using copper conductors?
- 14 AWG
- 12 AWG (Correct answer)
- 10 AWG
- 8 AWG
Correct answer: 12 AWG
12 AWG copper wire is rated for 20-amp circuits; using 14 AWG on a 20-amp breaker is undersized and a fire hazard.
Question 6: During an inspection, an AFCI breaker trips repeatedly when a specific circuit is tested. What does this most likely indicate?
- The AFCI breaker is oversized for the circuit
- An arcing fault condition exists somewhere on the circuit (Correct answer)
- The AFCI is incompatible with the panel brand
- The circuit is overloaded with too many outlets
Correct answer: An arcing fault condition exists somewhere on the circuit
AFCI breakers are designed to detect and interrupt arcing faults; repeated tripping suggests a wiring defect or damaged cord creating arc conditions.
Question 7: What is the significance of finding open-ground three-prong outlets in a home built in 1965?
- This was code-compliant at the time and requires no action
- The outlets were retrofitted with three-prong outlets without adding a ground conductor (Correct answer)
- This indicates aluminum wiring is present
- Open-ground outlets are only a concern in kitchens and bathrooms
Correct answer: The outlets were retrofitted with three-prong outlets without adding a ground conductor
Open-ground outlets indicate three-prong outlets were installed without a proper equipment ground, which removes shock protection for appliances.
InterNACHI Electrical Systems and Safety 3
What amperage rating is typically required for a dedicated 240V circuit serving a modern electric clothes dryer?