At Sol Rebel Power Systems, designing solar projects that balance utility requirements, safety, and cost-efficiency is our top priority. A common challenge we encounter in commercial and industrial solar projects is addressing ground fault detection and arc energy reduction on the AC side, particularly at the main AC disconnect switch.
Utilities often mandate that the AC disconnect switch be "visible open lockable." This requirement typically rules out rack-out breakers, pushing the need for blade-type disconnect switches. Many times, this means installing a bolted pressure switch (also called a Pringle switch) with integrated ground fault and arc energy reduction relays. While effective, these solutions come with challenges, including longer lead times, higher costs, and larger spatial footprints when integrated into switchboards.
Switchboard vs. Wall-Mounted or Stand-alone Disconnects
In some cases, switchboards with bolted pressure switches are the only option to meet utility and safety requirements. These switches, such as those offered by Eaton, integrate ground fault and arc energy relays and are housed within a switchboard section for ease of installation and operation. However, switchboards come with drawbacks:
Extended Lead Times: Custom switchboards take longer to procure, potentially delaying project timelines.
Higher Costs: Integrated solutions can increase upfront costs.
Larger Space Requirements: Switchboards require more real estate, which can be a challenge in space-constrained installations.
For projects where a switchboard isn’t strictly required, stand-alone wall-mounted disconnects may be a viable alternative. Options like the Eaton shunt trip safety switch or units from Bolt Switch provide ground fault and arc energy protection without the need for a full switchboard. These are particularly advantageous for smaller projects or where cost and space are significant concerns.
Enhancing Safety with Viewing Windows
Regardless of the type of disconnect solution used, viewing windows are a smart investment for enhancing worker safety. These windows allow personnel to verify the blade position of the disconnect without having to open a dead front, thereby reducing exposure to live parts and the risk of arc flash incidents.
Key Takeaways for Value Engineering
When designing systems to meet these NEC requirements, consider the following:
Understand Utility Requirements: Verify early in the design process whether a blade-type disconnect switch is required and if rack-out breakers are prohibited.
Evaluate Equipment Options: Determine if a switchboard is necessary or if a stand-alone safety switch could achieve compliance more cost-effectively. Particularly if there is a long distance from the main point of interconnection and the preferred location for your PV inverter combiner panel board, or where space is at a premium.
Plan for Lead Times: Factor in procurement timelines for switchboards and other custom equipment to avoid project delays.
Invest in Safety Features: Viewing windows and integrated arc energy reduction relays enhance safety while maintaining compliance.
Looking Ahead: Optimizing Safety and Uptime
In our next article, we’ll dive deeper into performing arc flash, short circuit, and coordination studies to ensure your system is not only safe but also optimized for maximum uptime. We’ll also explore ground fault protection considerations when multiple sources of ground fault current are present, such as in systems with solar PV and battery energy storage systems (BESS).
At Sol Rebel Power Systems, we’re committed to delivering innovative, safe, and cost-effective solar solutions. Contact us today to learn how we can help with your next project—and stay tuned for our next article in this series!
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