Electrical Distribution Parts 101

Power Panels
Power panels provide a central location for mounting inverters and charge controllers in battery systems and include enclosures for wiring, over-current protection, ground-fault and surge protection, bypasses and related hardware.

Fuses and Breakers
Fuses and breakers are designed to prevent excessive current from overheating conductors or devices by opening the circuit. Specialized breakers can also be deployed to open the circuit in case of ground or arc-fault conditions. Fuses and breakers should be sized according to NEC and/or manufacturer guidelines to ensure that they open the circuit before conductors or equipment can become damaged. See Reference for typical ampacity limits by wire size.

Surge Protection
Photovoltaic, wind, and hydroelectric systems usually have long runs of exposed wire that can pick up surges from lightning, even if it is not a direct lightning strike. These power surges can damage sensitive electronic components in meters, charge controllers, and inverters. Surges can also damage telephone, audio, and video equipment connected to the power system. It is a good idea to install surge protection on all incoming wires in the system, including incoming photovoltaic, wind, or hydroelectric power lines; AC generator lines; and telephone and antenna leads. Proper grounding is absolutely necessary for lightning protection to be effective. In the event of a direct strike, damage may occur, even with surge protectors installed. Type 1 heavy-duty surge protectors are recommended when a direct lightning strike is possible on the installation.

Proper equipment grounding helps to ensure that any electrical faults that may develop in a PV system have minimal opportunities to cause fires or electrical shocks. It is just as important to be familiar with NEC 250’s general grounding requirements when installing PV as it is to know 690. Jurisdictions and inspectors may vary on the grounding equipment and techniques they consider acceptable, so it is also important to know what your inspector will be looking for.

SnapNrack, as well as some other mounting system brands, now offer UL 2703 listed racking packages that incorporate much of the equipment grounding by bonding modules and related gear to the rails. However, not all equipment is considered compatible or likely to be accepted by a particular inspector, so it’s important to have some other options like those offered here.

Array Combiners
Array combiners are used to electrically combine the output of multiple series strings of PV modules into a single wire to simplify the connection to an inverter or charge controller. They typically include string-level overcurrent protection and sometimes host other functions such as monitoring, a disconnect, or even AFCI and remote shutdown. It is important that the combiner used be rated for the worst-case voltage and current the array can output.

Disconnect switches provide a means for safely opening a circuit between the power supply and any loads that may be present. Some disconnects also offer fusing, remotely-actuated contactors or other specialized functions. The NEC requires listed disconnects in a variety of situations. Be sure to choose a disconnect that is rated for the AC or DC voltage and current that may be present on the circuit.

Load Centers
Load centers provide a central location for mounting busses and breakers to feed multiple load circuits from a single power supply, such as a utility service or inverter output. The NEC requires NRTL-listed load centers for most applications. Be sure to choose a load center that is rated for the AC or DC voltage and current supplied as well as any application-specific requirements.

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