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 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.
Photovoltaic, wind, and hydroelectric systems usually have long runs of exposed wire that can pick up surges from lightning, even if the lightning strike is only nearby. 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 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 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.
Low-voltage power systems with inverters can have very high current through the cables that connect the inverter to the batteries. Large AC loads like microwave ovens, toasters, irons, and washers can cause an inverter operating on a 12 VDC battery system to draw over 100 A. Large motors may draw 300 to 500 A during startup. When cables between batteries, and from the battery bank to the inverter, are too small, the current available to the inverter is limited and it may fail to supply larger loads. Properly sized cables also impose less resistance and thereby help maximize system efficiency. Use this chart to find typical ampacity limits by wire size.
Array Cables and Connectors
Grid-tie modules generally ship with attached cables that are listed to UL 1703 with the module. The cable connectors on these are fully waterproof when connected, touch-protected and designed for up to 1,000 VDC and 30 A, but cannot be safely disconnected under load.
Our output cables are made with 10 AWG PV Wire and Amphenol H4 connectors, and can be used in solar arrays up to 1,000 VDC. All of our array output cables are made with PV wire that is listed to UL 854, which is required by the NEC for use with transformerless inverters.
Additionally, we stock the common styles of crimp-on connectors for use with 10 AWG PV stranded wire. Proper crimping to the wire and insulator assembly requires special tools.
Wire Management Hardware
As most experienced PV installers will attest, good wire management is a hallmark of high-quality installations, and its lack can lead to inspectors and customers alike looking for other potential issues. Cables and wires should be kept off the roof or ground and water should not be allowed to pool at the entrances of enclosures, splices and junction boxes. Given that a solar PV system is designed to last for 25 years or more, it is vital to use wire management hardware that will hold up in the environment and allow deployment with minimal strain on the components.
PV Cable Assembly Tools
Crimp-on PV cable connectors require special tools to properly attach the connectors. Single-purpose tools from Multi-Contact or Amphenol work with only that type of connector and are often the best option for installers who work only with modules that have that same connector type. For those who encounter several different types of connectors, one of the Rennsteig tool sets that have sets of dies and positioners can be more convenient and economical than carrying a different tool for each connector type.
System Survey and Commissioning Tools
Surveying and commissioning a PV system are important steps in the installation process, and it’s worth doing properly and consistently. Commissioning standards, such as IEC 62446 and related NABCEP guidelines, provide visual and physical inspections as well as electrical tests that should be performed prior to activating a new PV system. Common electrical tests made during commissioning include: continuity, phasing, and voltage for AC circuits; continuity of grounding conductors; DC circuit polarity verification; string I-V curves; string open-circuit voltage; string short circuit current; insulation resistance testing of PV source and output circuits; and, finally, a full-up system functionality test. With proper documentation, these same tests can be repeated periodically as systems age to ensure that they are operating efficiently.
Solar Safety Labels
The NEC and International Fire Code (IFC) require specific components of a PV system to be labeled for the safety of operators, maintenance, and emergency responder personnel. The Code also requires these labels to be appropriately weather resistant (IFC 605.11.1.1.3) and durable (NEC 110.21). These labels are UV and weather resistant and should meet Code requirements in most jurisdictions. Note that some jurisdictions may still require engraved placards. The labels are designed to permanently adhere to metallic, baked enamel, and powder-coated surfaces in most outdoor environments.
Local jurisdictions and company policies often call for unique language or types of labels that are not available in preprinted form. If this is a frequent requirement, a label printing system can be an economical way to get exactly what you need when you need it. The ability to produce custom labels also presents opportunities for branding as well as organization, theft prevention, and identification.