Codes and standards ensure safe construction of photovoltaic systems

By Scott Jezwinski

Photovoltaic (PV) systems are being installed at an ever increasing rate in North America. Fueled by renewable energy policy and incentives, solar-generated electricity has begun the trek across the chasm into mainstream. The industry continues to rally around the momentum created by low module prices, reduced soft costs, and continuous performance improvements resulting in repeated increased annual installations.

While clean electricity generated from solar PV is making headway in the presence of greenhouse gas emitting fossil fuels, almost all forms of generation produce electricity at high voltages and potentially lethal currents. For over 100 years, society has coexisted with large power plants, central generation, and dangerous high voltages distributed on cables stretched across the country in the air or underground and more or less out of reach and harm's way. With the increasing presence of PV systems within reach on rooftops, in backyards, and across the street in open fields, the solar industry must be vigilant in the construction of safe, reliable, and durable PV electricity generation.

Standards are a way of reducing risk by introducing consistency to essential design features, performance benchmarks, and above all, safety requirements. UL published the first PV Standard, ANSI/UL 1703, Safety of Flat-Plate Photovoltaic Modules and Panels, in 1986 and since that time has published more than 16 additional standards and outlines covering other balance of systems. Collaboratively developed by manufacturers, code authorities, national labs, government agencies, and other interests, the standards embody requirements and definition for components, products, and systems.

Vigilance begins with application of these standards to the supply chain and the materials and components that go into the end product, such as PV modules. Evaluating materials to extreme environmental conditions and deteriorating effects of UV rays, heat, and moisture is akin to assessing the integrity of links in a chain. Just like a chain, an end product is only as good as the materials and components from which it is constructed. Testing the end products is equally important and provides a critical assessment of the PV module, for example, to withstand the mechanical and thermal stresses when installed and operating. The manufacturer is authorized to apply a certification mark on the product, such as the UL label, after compliant results have been achieved. Application of the label is a manufacturer's attestation of consistency in production and reassures the inspectors, buyers, owners, and operators that the installed products were properly evaluated.

Additionally, a system level evaluation of PV modules and mounting means is performed emphasizing proper bonding and the ability to withstand various stressors and corrosive effects while in operation. Also, the integrity of the grounding scheme is examined to promote safety when PV modules are energized.

In the field, codes such as the National Electrical Code (NEC), NFPA 70, govern the installation of solar photovoltaic systems. The NEC provides the foundation for inspections and approvals in the U.S. Early chapters apply to electrical systems in general, and cover installation requirements, wiring methods, and materials. Article 690 covers specific requirements for photovoltaic systems, and article 705 covers requirements for interconnecting PV systems to the utility grid. The NEC does not specifically address PV performance, but rather establishes requirements to ensure the overall quality and safety of the installation.

Other standards may also apply depending on the local authorities and the needs of system stakeholders. For example, the international standard IEC 62446, Grid connected photovoltaic systems – Minimum requirements for system documentation, commissioning tests, and inspection, provides guidance during the design, construction, and maintenance phases of a development.

Personnel conducting testing on PV systems should be qualified individuals having knowledge and experience with electrical systems, the hazards involved, and how to test them. Work practices and related measures should be consistent with requirements in NFPA 70E, Standard for Electrical Safety in the Workplace, and Title 29 regulations of the U.S. Occupational Safety and Health Administration (OSHA), including 29 CFR Part 1926.

Adoption of the NEC by states and local jurisdictions provides the basis for inspections and approvals of PV systems in North America. The UL product safety standards are the basis for evaluation of PV modules, inverters, and remaining balance of system equipment. Knowledge and understanding of these codes and standards are essential in the planning and design of PV systems and factor into the financial success of the project. The late discovery of non-compliances during construction can be costly to correct and quickly turn a profitable project into a losing one. For example, modules, mounting schemes, inverters, or equipment that is not properly tested and certified are costly to replace once installed. A simple oversight such as not following the manufacturer's installation instructions may introduce bonding/grounding issues, a critical safety concern and costly to rework.

Beginning with the earliest PV installations, UL has provided assistance to manufacturers, owners, developers, and engineering, procurement, and construction (EPCs) firms with access to knowledge, services, and training enabling the safe deployment of residential, commercial, and utility scale systems world-wide.

The number of safety concerns can be dizzying, but the risk can be managed by building and testing products to standards and installing them according to applicable codes by installers qualified to do the job. By partnering with manufacturers and installers, UL is able to help them understand and mitigate such risks through compliance with installation and building codes and incorporation of hazard-based safety engineering into their designs. These actions in collaboration ensure safe, high quality solar PV electricity generation remains in our future.

Scott Jezwinski, Business Development Manager – Energy and Industrial Systems at UL LLC, (www.ul.com) is responsible for leading UL's collaboration within the PV and other energy sectors in North America, including working with key industry stakeholders, industry associations, manufacturers, and regulators. He is also responsible for the development of standards, test methods, and evaluation of photovoltaic products and systems.

 
March/April 2014