NEC stands for the National Electric Code, which for more than a century has comprised a list of electrical best practices for homes and businesses in the United States. Updated every three years, the NEC sets the stage for evolving electrical design and installation practices, and while not legally binding is a de facto guide in developing regional building codes.
The 2014 NEC contains key changes relating to photovoltaic (PV) installations, with the goal of making PV systems safer for building owners and occupants, service technicians and first responders. In order for the PV sector to grow safely and successfully in the U.S., the design and installation of PV systems must be able to meet minimum NEC standards.
ABB products can help PV systems comply with all PV-related changes in the NEC.
Additional protection
For example, NEC section 690.5(A) dealing with ground-fault detection and interruption was revised to provide additional protection from high impedance and multiple ground faults in PV systems.
ABB helps PV customers comply with its S804U-PVS5 ground fault detector interrupter. Developed to meet the requirements of PV systems, this UL listed high-performance circuit breaker is rated for 1,000 volts (V) DC, provides a thermal tripping mechanism for overload protection and an electromechanical tripping mechanism for short circuit protection.
As PV technology expands and evolves, traditional 600 DC voltage levels in domestic installations above a certain size are increasingly being supplanted by 1,000 V DC levels that were once mostly used by utilities. The NEC must ensure that 1,000 V DC systems can be installed as safely as 600 V DC systems.
The NEC section 690.9 update outlines hardware requirements for overcurrent protection of PV source and output circuits, to ensure hardware is specifically designed for PV systems.
UL listed ABB Tmax PV automatic molded-case circuit breakers provides overcurrent protection for systems up to 1,000 VDC. ABB understands fully the challenges of protecting and opening DC currents, which are more difficult to manage than AC currents because the voltage remains constant. Unlike AC circuits, which have a voltage waveform that is continuously passing through 0 VDC each cycle, a constant DC voltage means that any opening arcs must be extinguished using other, more advanced methods. This is why NEC 2014 now requires the use of products that are specifically designed for PV and why ABB has been so successful with our patented DC technologies.
Rapid shutdown
NEC section 690.12 introduces significant changes dealing with the rapid shutdown of PV systems on buildings to safeguard, for example, emergency services personnel. To minimize shock hazard, there are now requirements for the immediate removal of power in specific areas of the PV installation that emergency personnel may come in contact with.
ABB provides several solutions for this new requirement, including deployment of ABB Micro inverters to control solar panel outputs individually, or ABB’s PV Vault UL listed solution, which has been specifically designed to meet NEC requirements for rapid emergency shutdown in all PV system configurations.
Section 690.35(C) deals with ground fault protection in ungrounded PV systems, requiring that all PV circuits be protected by a listed ground-fault protection device or system. For this ABB provides UL listed PV inverters with integrated arc fault protection functionality, as well as ABB CM-IWN.1 insulation monitoring relays that are UL listed up to 600 V DC, or up to 1,000 V DC with the CM-IVN coupling unit, which sends feedback to the inverter to stop supplying power underground fault conditions.
Grounding and disconnect systems
Section 690.41 requires PV systems to comply with NEC guidelines regarding system grounding. ABB’s Thomas and Betts’ furse earthing and lightning protection product line delivers UL listed copper tapes, tape-to-rod clamps, copper-to-aluminum joints and many other grounding solutions.
The Thomas and Betts furse product line also includes multiple UL listed ground rod solutions that will also help customers to be compliant with NEC section 690.47(D), which was accidentally omitted from the last NEC update in 2011. It is back now, and requires a compliant and directly-connected auxiliary grounding electrode to be installed as close as possible to the PV array to help protect against lightning strikes, which may be more likely because of the quantity of conductive material in a PV installation.
NEC Section 690.71(H) covers battery storage locations and disconnect systems. ABB’s OTDC disconnect switches are UL listed and can be used in conjunction with fuses at the energy storage device, or as a secondary means of disconnecting at the connected equipment.
The ABB LV advantage
ABB delivers a wide range of reliable, innovative products designed for photovoltaic applications that meet all installation requirements, from the PV strings to the utility grid connection point, including circuit breakers, switch and fuse disconnectors and fuses, ground fault detection devices, grid connection relays, metering devices, surge arresters, as well as the enclosures needed to protect these devices from the hot and harsh environments that are often unavoidable in PV installations.
ABB plug and play LV solutions for PV systems provide finished, wired and certified string boxes suitable for a vast range of installations, from individual strings for residential applications to large photovoltaic plants.
Useful links
– General
– National Fire Protection Association (Editor of the NEC code)
– ABB Solar
– Low-voltage products for solar power
– Solar power solutions