NABCEP - Certified North American Board of Certified Energy Practitioners Specialist NEC Article 690 Applications Questions and Answers — Questions and Answers
Question 1: According to NEC Article 690, which of the following is a primary requirement for the location of a PV system disconnecting means?
- It must be within sight of the PV array.
- It must be located on the roof within 6 feet of the array.
- It must be installed in a readily accessible location. (Correct answer)
- It must be located exclusively inside the building near the main service panel.
Correct answer: It must be installed in a readily accessible location.
NEC 690.13 mandates that the PV system disconnecting means be installed in a 'readily accessible location'. This ensures that first responders and qualified personnel can quickly and safely de-energize the system without needing ladders or removing obstacles.
Question 2: A rooftop PV system is being installed on a single-family dwelling. Per NEC 690.12, what are the voltage and time limitations for controlled conductors *inside* the array boundary after rapid shutdown is initiated?
- 30 volts within 10 seconds
- 80 volts within 30 seconds (Correct answer)
- 120 volts within 60 seconds
- 30 volts within 30 seconds
Correct answer: 80 volts within 30 seconds
NEC 690.12(B)(2) requires that for PV systems on buildings, controlled conductors inside the array boundary shall be limited to not more than 80 volts within 30 seconds of initiating rapid shutdown. This is a critical safety measure for firefighters.
Question 3: When calculating the required ampacity for PV source circuit conductors, what multiplier is applied to the module's short-circuit current (Isc)?
- 100%
- 110%
- 156%
- 125% (Correct answer)
Correct answer: 125%
NEC 690.8(A)(1) requires that the maximum current for sizing conductors and overcurrent protection be calculated as 125% of the PV module's short-circuit current (Isc) to account for periods of higher-than-standard irradiance.
Question 4: Which of the following is required by NEC Article 690 regarding the grounding of a grid-tied PV system installed on a building?
- A separate grounding electrode must always be installed at the array location.
- Only the DC equipment needs to be grounded; the AC side is covered by the main service.
- Exposed non-current-carrying metal parts, like module frames and racking, must be bonded and connected to an equipment grounding conductor. (Correct answer)
- Functional grounding is prohibited for all PV systems.
Correct answer: Exposed non-current-carrying metal parts, like module frames and racking, must be bonded and connected to an equipment grounding conductor.
NEC 690.43 requires that exposed non-current-carrying metal parts of the PV system, including module frames, racking, and enclosures, must be bonded together and connected to an equipment grounding conductor (EGC) to create a safe path for fault current. While a separate grounding electrode is sometimes used, it is not always required and the system EGC often connects to the building's existing grounding electrode system.
Question 5: An installer is running PV source circuits from a rooftop array through the attic to a string inverter in the garage. According to NEC 690.31, which wiring method is typically required once the conductors penetrate the building?
- The conductors must be installed in a metallic raceway or be a Type MC cable. (Correct answer)
- Direct-burial rated USE-2 cable can be run without conduit inside the building.
- The conductors can be run without a raceway as long as they are secured every 4.5 feet.
- Any listed cable suitable for wet locations is acceptable.
Correct answer: The conductors must be installed in a metallic raceway or be a Type MC cable.
NEC 690.31(C)(1) generally requires that when PV source or output circuits penetrate a building, they must be installed in a metal raceway, such as EMT, or be a metal-clad (Type MC) cable from the point of penetration to the first readily accessible disconnecting means. This provides physical protection and a grounded path for the conductors inside the building.
Question 6: For a PV system operating at 96V DC on the roof of a commercial building, what specific type of protection is required by NEC 690.11 to mitigate fire hazards?
- Ground-fault circuit-interrupter (GFCI) protection
- Surge protective device (SPD)
- DC arc-fault circuit protection (AFCI) (Correct answer)
- Reverse-current protection
Correct answer: DC arc-fault circuit protection (AFCI)
NEC 690.11 mandates the use of listed DC arc-fault circuit protection for PV systems with a DC voltage of 80V or greater that are installed on or in buildings. This device is designed to detect and interrupt arcing faults that could otherwise create a serious fire hazard.
NABCEP - Certified North American Board of Certified Energy Practitioners Specialist NEC Article 690 Applications Questions and Answers
According to NEC Article 690, which of the following is a primary requirement for the location of a PV system disconnecting means?