UL 3741 listed systems, or PV hazard control system (PVHCS) as they were termed in NEC 2023, are a hot topic in C&I solar. UL 3741 provides an alternative to the previous sole solution of utilizing MLPEs on all rooftop PV arrays to meet the 690.12 requirements for conductors inside the array boundary. From the Solar Builder archives:
NEC 690.12(B)(2) calls out the use of these systems to “provide shock hazard control for firefighters” as one method to meet the requirements to control the conductor limits within the array boundary. The addition of “provide shock hazard control for firefighters” is also added to 690.12(B)(2) to help clarify the purpose of these systems and who they serve.
Racking, wire management, and inverter manufacturers must then be listed together as a single PVHCS. Example: Sollega’s solar racking solutions combined with Solis’ commercial inverters.
Established in 2005, Solis is one of the most experienced and largest manufacturers of PV string inverters. The company’s portfolio uses innovative string inverter technology to deliver first-class reliability that has been validated under the most stringent international certifications.
The Solis S5-GC(75-100)K inverter is the preferred commercial PV string inverter and a UL 3741 alternative to MLRSD. The inverter features 10 independent MPPTs with wide full-power operating ranges that can work efficiently with both 600Vdc and 1000 Vdc PV arrays. String current up to 16A perfectly accommodates new high-power and bi-facial PV modules.
Sollega’s simple racking solutions include 5º, 6º, and 10º tilt options that are modular, one-piece designs. The install process is comprised of 3 quick steps:
- Position FastRacks
- Add ballast and clamps
- Attach any framed modules to the universal design
Their solutions have fully ballasted, heat welded, anchored, and hybrid options with engineering and ballast layout services available on demand. The round edges and low point loads make it great for roofs. The mounts have been tested and have a Class “A” Fire Rating Type 1, 2, 3 & 29 modules. They are 100% recyclable and made in the US. Combined with Solis Inverters, the full system is safe, reliable, and easy to install, allowing customers to save a significant amount of time and money. Contact them directly at https://sollega.com/contact. Sollega sells direct to installers.
“Sollega racking solutions are unique in the marketplace and optimized for firefighter safety at first response,” says Terence Parker, Solis Compliance/Application Engineering Manager. “Solis inverters are known for their reliable and safe operation in extreme environments. We are excited about partnering with the innovative Sollega team and rooftop PV installers across North America to reduce installation times and costs with our safe and reliable combined system.”
Beyond the safety and code implications, UL-listed PVHCS can have longer term benefits. With Solis in particular, online tools make O&M more intelligent and convenient for the customer while optimized DC & AC interconnection will reduce the cost of system cables. Enclosures rated to IP66 protection grade can be installed in the harshest environmental conditions so that you have one less thing to worry about during storms and natural disasters.
The protection grade proves that the inverters’ durability will stand the test of time And on top of all that, the 100K inverter also meets NEC 690.12 PV rapid shutdown requirements without MLPE or mid-circuit interrupters.
Solis also touts its service as one of the best in the industry. You can easily get on the phone with one of the many local Service Engineers that are happy to help with any troubleshooting, installation, or commissioning questions.
For more on designing PV systems listed to UL 3741, or Solis products, email the Solis USA team here.
— Solar Builder magazine
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