NABCEP NEC Article 690 Applications 4 — Questions and Answers
Question 1: NEC 690.71(A) covers storage batteries used with PV systems. What minimum voltage requirement applies to battery installations in dwelling units?
- Battery systems must not exceed 50 V dc nominal (Correct answer)
- Battery systems in dwellings must use only sealed, valve-regulated batteries
- Battery nominal voltage must not exceed the system voltage limits of Article 690
- There is no voltage restriction for dwelling battery systems
Correct answer: Battery systems must not exceed 50 V dc nominal
NEC 690.71(A) limits battery systems in dwelling units to 50 V dc nominal or less to reduce shock hazard in residential applications.
Question 2: Per NEC 690.74, battery interconnect conductors must be sized for at least what percentage of the rated ampacity required for the circuit?
- 100%
- 125% (Correct answer)
- 156%
- 80%
Correct answer: 125%
NEC 690.74 requires battery interconnect conductors to be sized at 125% of the maximum current for which the circuit is rated.
Question 3: According to NEC 690.72, what device is required to prevent overcharging of batteries in a PV system?
- A manual disconnect switch at the battery terminals
- A charge controller or other approved current-limiting means (Correct answer)
- An overcurrent protective device rated at 80% of battery capacity
- A bidirectional inverter only
Correct answer: A charge controller or other approved current-limiting means
NEC 690.72 requires a listed charge controller or other approved means to prevent overcharging and potential battery damage or fire.
Question 4: NEC 690.10 sets maximum voltage limits for PV systems on one- and two-family dwellings. What is the maximum system voltage for these residential installations?
- 300 V dc
- 600 V dc (Correct answer)
- 1000 V dc
- 1500 V dc
Correct answer: 600 V dc
NEC 690.10 limits PV systems on one- and two-family dwellings to a maximum system voltage of 600 V dc.
Question 5: When an inverter is used in a PV system, NEC 690.60 requires that inverters listed for interactive operation must be listed and identified for use with which type of system?
- Stand-alone systems only
- Interactive (utility-interactive or grid-tied) systems (Correct answer)
- Both stand-alone and interactive systems simultaneously
- Battery backup systems only
Correct answer: Interactive (utility-interactive or grid-tied) systems
NEC 690.60 requires inverters for grid-tied applications to be listed and identified for utility-interactive operation to ensure safety and compatibility.
Question 6: NEC 690.64 addresses the point of connection for PV systems to a distribution system. What limitation applies to the sum of all power sources connected to a busbar?
- The combined current ratings must not exceed 150% of the busbar rating
- The combined current ratings must not exceed 120% of the busbar rating (Correct answer)
- The power sources must not exceed 50% of the busbar rating
- No limitation applies as long as overcurrent protection is provided
Correct answer: The combined current ratings must not exceed 120% of the busbar rating
Per NEC 690.64, the sum of the ampere ratings of all overcurrent devices on a busbar must not exceed 120% of the busbar's ampere rating.
Question 7: For a stand-alone PV system powering a dwelling, NEC 690.10(C) requires the system to meet which additional code requirement?
- It must have a utility interconnection as a backup
- It must supply the loads in compliance with NEC Article 230 requirements (Correct answer)
- It must include a generator transfer switch
- All wiring must be in metal conduit
Correct answer: It must supply the loads in compliance with NEC Article 230 requirements
NEC 690.10(C) requires stand-alone systems to supply loads at voltages complying with NEC Article 230, maintaining safe voltage levels for premises wiring.
NABCEP NEC Article 690 Applications 4
NEC 690.71(A) covers storage batteries used with PV systems.
What minimum voltage requirement applies to battery installations in dwelling units?