Quick Answer
Off-grid panels can be wired in both series and parallel configurations, but each configuration has its own set of rules and limitations. Series wiring is typically used for high-voltage applications, while parallel wiring is more common for off-grid systems. Series wiring should be done with great care, as it can lead to significant power losses.
Series Wiring
Series wiring is used when panels are connected end-to-end, with the positive terminal of one panel connected to the negative terminal of the next. This configuration is typically used for high-voltage applications where the voltage needs to be stepped down. For example, a 48V system might be wired in series with 4 panels of 12V each, resulting in a total of 48V. However, in off-grid systems, series wiring is less common due to the high power losses it incurs. A 12V panel wired in series will only produce 6V, resulting in a significant reduction in power output. Series wiring also requires a more complex and expensive system, with each panel needing to be individually protected by a fuse or circuit breaker.
Parallel Wiring
Parallel wiring is the most common configuration for off-grid systems. In a parallel configuration, the positive and negative terminals of each panel are connected together, allowing the system to take advantage of the total power output of all the panels. This configuration is ideal for off-grid systems, as it allows for easy expansion and maintenance. For example, 4 panels of 12V each can be wired in parallel to produce a total of 48V. Each panel should be protected by a fuse or circuit breaker, and the system should be grounded according to NEC code 250.30. The total current rating of the breakers should be calculated according to NEC 215.2(A)(3), which states that the total current rating should be at least 125% of the total load.
Subpanel and Grounding Requirements
A subpanel is required when the total wattage of the system exceeds 400 watts. The subpanel should be installed in a location that is easily accessible and protected from the elements. The subpanel should be wired according to NEC code 210.8, which requires that the main breaker be sized according to NEC 215.2(A)(3). The system should be grounded according to NEC code 250.30, which requires that the grounding system be sized according to NEC 250.66. The ground rod should be driven to a depth of at least 8 feet, and the grounding strap should be sized according to NEC 250.66.
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