The solar world is dominated by news of the latest, greatest modules, easier-to-use and more streamlined mounts, and the newest inverter technology. But what is often overlooked is everything in between—like wiring and conduit.
While there may be exposed conductors behind the modules, once PV circuits leave the array, conduit becomes a necessary part of each project—the raceways protect source wires and inverter outputs from damage. It protects our homes and families from the inherent dangers of electricity. When poorly implemented, conduit can turn an install into an eyesore. Well-done conduit, on the other hand, can set your installation apart from others.
The initial site assessment will help determine array placement and size, and identify limitations of the installation. Once array and balance of system (BOS) locations are determined, potential conduit runs should be investigated. The primary considerations are overall aesthetics, creating the most efficient runs, and adherence to the National Electrical Code (NEC).
Assessing a raceway must be done before a design is finalized for several reasons. Wire size is dependent upon conduit length and temperature differentials along the route, and in turn conduit size is based on the type, size and number of conductors within (watch for a future article on conduit sizing). If these factors are not considered, the project may be completed with conduit too small for the correct wire size or wire too small for the installation.
Roof Mounts. When faced with a typical roof-mount installation, the first step is to check for attic access. While checking structural support for the array, a raceway path should be determined. Attics are often somewhat open and can present a pathway to the BOS equipment. If you are lucky, a chase will lead directly to the area where the inverter is to be located. However, you may be working with a vaulted ceiling that cannot be penetrated, or with multiple attics with no access between, which will require routing external conduit.
BOS location must be Code-compliant first and foremost, but aesthetics must also be taken into consideration. The logical place to mount equipment may be in the worst possible area visually.
Pole Mounts. In determining conduit runs for a pole mount, the type of mounting system makes a difference. Many pole mounts have hollow bodies in which wiring can be routed to a junction box at the mount’s bottom. Other poles are NEMA-rated to allow wiring to be spliced inside the pole body. If the pole is rated to contain wires, then they can be used with internal conduit. Most often, they are not and require external conduit. In areas where moisture is not an issue, but sharp edges are, split-loom tubing is necessary. To protect wires inside a pole, ensure bushings are used on all fittings. Split-loom tubing may be used near sharp edges for additional protection. If access to the pole is not available, however, conduit may be installed on the outside of the pole to take source wires to the BOS equipment.
Ground Mounts & Awnings. Ground mounts, awnings, and pole mounts typically have the same conduit goal—take wire from the modules or junction box through a trench to the BOS equipment. Should the BOS equipment or disconnects be located at the array, routing conduit between equipment will be a concern. Knowing where the BOS components are located, the trench location, and the array string layout will be extremely important in determining conduit routing.