What is in this article?:
- Troubleshooting Small-Scale Photovoltaic (PV) Systems
- SIDEBAR: PV System Notes
- SIDEBAR: Safety Warning
Electrical contractors can gain confidence and experience with photovoltaic (PV) systems by performing basic troubleshooting practices on string inverter-based equipment
SIDEBAR: PV System Notes
All module frames must be bonded — lugs and wire shown — but other methods, such as special clips, may be used. The allowed number of series modules depends on the inverter design and local low temperature values.
Most inverters have the ability to display operational data and fault information on a digital display. A typical string inverter design is shown in this example. Note: There are other designs available, such as microinverters. The inverter may be marked for positive or negative ground (some PV modules perform better with a specific polarity). Note: No polarity is shown on this diagram. The inverter will likely have a fuse for detecting an array wiring ground fault. Some inverters do not ground reference either polarity of the array and use other methods to detect a ground fault.
Wiring exposed to sunshine must be rated for this exposure. Conduits and junction boxes must be bonded if containing conductors rated 250V (applies to both AC and DC systems) or greater. Note: Exposure to sunshine affects required wire size.
More than two module strings in parallel must have fuse protection per module listing. Fuses may be located in a DC combiner enclosure or in the inverter. DC disconnects may be separate, or part of the combiner or inverter.
The drawing illustrates a 3-phase system, but a single-phase system follows the same general design.
A separate kWh meter may be included in the design to record the energy generated by the PV system.
Many electric utilities require the inclusion of a separate lockable AC disconnect switch that is readily accessible to utility crews. These disconnects typically do not have fuses, and access may be locked by an electric utility padlock. Some utilities require a separate GEC bond from the inverter to the main service ground.
The drawing shows a load side connection of the inverter circuit to the service entrance. The circuit breaker is typically required to be on the opposite end of the distribution buss from the main circuit breaker and must be marked.
Labels specifying voltage and current values are required on many components in the system.
Refer to NEC Art. 690 for additional requirements.