Photovoltaic modules installed on top of covered parking areas, also known as solar carports, are multi-purpose structures that maximize space and produce power. These contemporary systems offer keen insight into current solar industry innovations. However, many solar carport manufacturers lack lightning protection or grounding advice for pre-engineered products or mounted solar panels.
This ambiguity from manufacturers concedes potential unfavorable implications. A long-lasting, effective, and code-compliant grounding system is vital for protection and safety and for maintaining the lifespan of the equipment. The following article highlights the most common type of carport sold in North America, a galvanized steel structure set into or onto a drilled concrete pier.
Carport manufacturers generally do not supply an engineered structure foundation or electrical engineering details. A carport-mounted solar array can carry DC and AC devices with fault current potential for both. The first step in developing a grounding scheme for the completed PV system is to examine the foundation structure as soon as it is available. The length and attachment method of the steel post and pier may or may not qualify the design as a grounding conductor. Refer to NEC 250.68(C)(2) and NEC 250 to get started. A detail as simple as tying the anchor bolts of the carport post to the rebar of the foundation can result in an exemplary and no-added-cost grounding system.
Refer to the following example scenario as a checklist for grounding your solar carport system:
Grounding the Solar Array
In this example, we will connect the module to the purlin using WEEB DSK38 washers. Situate the WEEB DSK38 washer between the module frame and the purlin for optimal contact with both. Tighten the module mounting bolt to the specified torque, ensuring the washer's teeth penetrate the anodized coatings on the module frame and purlin. Visually confirm the washer's teeth have embedded into both the module frame and the purlin.
Use the same WEEB DSK38 washers to connect the purlin to the rafter. Position another WEEB DSK38 washer between the purlin and the galvanized steel rafter to create an electrically conductive pathway. Secure the purlin to the rafter, ensuring the washer bites into both surfaces. Ensure the washer provides a solid contact between the purlin and the rafter.
Grounding Conductor to Ufer Ground Connection
Refer to NEC Section 250.52(A)(3) concerning concrete-encased electrodes, commonly referred to as "Ufer grounds," for further information regarding this step. Connect the copper grounding wire from the rafter's grounding lug to the Ufer ground. Ensure a secure connection and validate that the resistance between the rafter and ground is as low as possible, aiming for less than 1 ohm. Employ a continuity tester to confirm a continuous path from the modules, through the purlins, to the rafters, and finally, to the ground.
Lightning Protection
Protecting a solar carport from lightning strikes is crucial to the safety of both human life and the system itself. First, integrate a lightning arrestor within the solar installation. Ensure the lightning protection system is interconnected with the main grounding system. Regularly inspect and maintain the lightning protection system to ensure its effectiveness.
Local Codes & Regulations
It is important to always abide by the NEC, specifically referencing Section 250 for grounding and bonding essentials. Once you have successfully set up your grounding scheme, seek any necessary inspections or approvals from local governing bodies.
Maintenance & Periodic Checks
It is also crucial to conduct periodic evaluations for corrosion, loose connections, or other potential issues on a solar carport system. Adjust or replace components as needed.
The solar carport's integrity will rely on periodic checks and professional consultations to ensure safe handling and longevity of the system. It is highly recommended to always consult with a licensed professional to ensure the safety, efficacy, and compliance of your grounding system, specifically when integrating complex elements like lightning protection and Ufer grounds.
The Greentech Renewables Design Services team is here to support you through every step of the installation process. Connect with us today or leave your comment below to inquire further about grounding your solar carport system.