Mike Holt s Illustrated Guide to SOLAR PV SYSTEMS

Transcription

1 Mike Holt s Illustrated Guide to Directory, Identification, Label, Marking, Plaque, and Sign Requirements for SOLAR PV SYSTEMS Extracted From Mike Holt s Illustrated Guide to Understanding NEC Requirements for Solar Photovoltaic Systems For more information about this book and other Solar PV products visit NEC, NFPA 70, NFPA 70E and National Electrical Code are registered trademarks of the National Fire Protection Association. Mike Holt Enterprises, Inc NEC.CODE Info@MikeHolt.com COPYRIGHT 2011 Charles Michael Holt

2 ARTICLE 690 Solar Photovoltaic (PV) Systems Introduction to Article 690 Solar Photovoltaic (PV) Systems You ve seen, or maybe own, photocell-powered devices such as night lights, car coolers, and toys. These generally consist of a small solar panel and a small light or motor. Typically, these run on less than 10V dc and draw only a fraction of an ampere. These kinds of devices are very different from a system that can power a house or interconnect with a utility to offset a building s energy consumption. Consider the sheer size and weight of solar modules for providing electrical power to a building. You re looking at mechanical and site selection issues that may require specialized expertise. The value of these modules also means there are security issues to consider, which may require more than just installing locks. There are also civil and architectural issues to address. In summary, these installations are complicated and require expertise in several non-electrical areas, which the NEC doesn t address. Article 690 focuses on reducing the electrical hazards that may arise from installing and operating a solar photovoltaic system, to the point where it can be considered safe for property and people. This article consists of eight Parts, but the general requirements of Chapters 1 through 4 apply to these installations, except as specifically modified by Article 690. Part I. General Scope. Article 690 applies to photovoltaic (PV) electrical energy systems, array circuit(s), inverter(s), and charge controller(s) for PV systems, which may be interactive with other electrical power sources (electric utility) or stand-alone with or without energy storage (batteries). Figures and Figure Installation. (B) Identification and Grouping. PV system conductors, both dc and ac, can be installed in the same raceways, outlet and junction boxes, or similar fittings with each other, but must be kept entirely independent of non-pv system wiring conductors. Figure Figure Mike Holt Enterprises, Inc NEC.CODE ( ) 1

3 Ex: Identification of different systems isn t required where conductor identification is evident by spacing or arrangement. (F) Circuit Routing. PV source and output conductors must be routed along building structural members (beams, rafters, trusses, and columns) where the location of those structural members can be determined by observation. The location of PV source and output conductors imbedded in built-up, laminate, or membrane roofing materials in areas not covered by PV modules and associated equipment must be clearly marked. Figure PV system conductors must be identified by separate color coding, marking tape, tagging, or other approved means and grouped as follows: (1) PV Source Circuits. Identified at points of termination, connection, and splices. (H) Multiple Inverters. Where multiple utility-interactive inverters are located remote from each other, a directory is required at each dc PV system disconnecting means, at each ac disconnecting means, and at the main service disconnecting means showing the location of all ac and dc PV system disconnecting means in the building/structure. Ex: A directory isn t required where all PV system disconnecting means are grouped at the service disconnecting means Ground-Fault Protection. PV systems must have ground-fault protection to reduce fire hazards. Figure (2) PV Output and Inverter Circuits. Identified at points of termination, connection, and splices. (3) Multiple Systems. Conductors of each system must be identified at termination, connection, and splice points. Figure Figure (C) Labels and Markings. A warning label must be on the utilityinteractive inverter stating the following: Figure Figure WARNING ELECTRIC SHOCK HAZARD IF A GROUND FAULT IS INDICATED, NORMALLY GROUNDED CONDUCTORS MAY BE UNGROUNDED AND ENERGIZED Mike Holt Enterprises, Inc NEC.CODE ( ) 2

4 Figure Figure Caution: The label must resist the environment for 25 to 40 years of system use and be suitable for the environment and be installed so as not to void equipment listing [110.3(B)]. When plastic is used, it should not be placed in direct sunlight, unless specifically manufactured as sunlight resistant; a metallic engraved sign would be best. Part II. Circuit Requirements Stand-Alone Systems. (C) Single 120V Supply. The battery based inverter output is permitted to supply a 120V single-phase, 3-wire, 120/240V distribution panel marked with the following words or equivalent: (4) A permanent plaque identifying the locations of the service and inverter ac disconnect(s) must be placed at service and inverter ac disconnect(s) locations PV Equipment Disconnect. PV equipment must have a disconnecting means that opens all ungrounded circuit conductors from all sources of power. Where equipment is energized from more than one source, such as an inverter supplied by dc current input from the array and ac current output to the utility source, a disconnecting means is required for each and both dc and ac disconnects must be grouped together and each permanently marked to identify their purpose. Figure WARNING SINGLE 120-VOLT SUPPLY DO NOT CONNECT MULTIWIRE BRANCH CIRCUITS Part III. Disconnecting Means PV System Disconnecting Means. (C) Requirements for Disconnecting Means. The PV system disconnect must open all ungrounded conductors. (2) Marking. Each PV system disconnect must be permanently marked to identify it as the PV system disconnect. Figure (D) Inverter Disconnects. Where utility-interactive inverters are not readily accessible, dc and ac circuit disconnecting means is requires as follows: Figure Mike Holt Enterprises, Inc NEC.CODE ( ) 3

5 Disconnecting Means for Fuses (B) PV Output Circuit. A disconnecting means must be provided for PV output circuits. Where the disconnecting means is more than 6 ft from the fuse, a directory indicating the location of the fuse disconnect must be at the fuse location. Figure Disconnect Requirement. Disconnects must be a manually operable switch or circuit breaker meeting all of the following: (4)For dc disconnects where line and load terminals will be energized when the switch is in the open position, a warning sign must be placed on or adjacent to the disconnect such as: Figure Figure Figure Nonload-break fuse pullouts or holders must be marked Do not open under load. Figure WARNING ELECTRIC SHOCK HAZARD DO NOT TOUCH TERMINALS TERMINALS ON BOTH THE LINE AND LOAD SIDES MAY BE ENERGIZED IN THE OPEN POSITION Part IV. Wiring Methods Wiring Methods. (E) Circuits Inside Buildings/Structures. (3) Marking/Labeling. Wiring methods and enclosures containing PV dc conductors must be marked Photovoltaic Power Source by labels or other approved permanent marking means. Figure Figure (4) Marking /Labeling Methods. The marking required by (E) (3) must be visible after installation and appear on every section of the wiring system separated by enclosures, walls, partitions, ceilings, or floors. Spacing between labels/marking must not be more than 10 ft and labels must be suitable for the environment. Figure Ungrounded Systems. PV power systems are permitted to be ungrounded if they comply with the following: Mike Holt Enterprises, Inc NEC.CODE ( ) 4

6 (1) Rated maximum power-point current (Imp x number of combined paralleled source circuits). (2) Rated maximum power-point voltage (Vmp x number of modules in each source circuit). (3) Maximum system voltage (Voc). Note: See 690.7(A) for maximum photovoltaic system voltage calculation. (4) Short-Circuit Current (Isc x 1.25). Note: See 690.8(A) for maximum circuit current calculation. Figure Author s Comment: The values for maximum power-point current (Imp), maximum power-point voltage (Vmp), open circuit voltage (Voc), and short-circuit current (Isc) are indicated on the manufactures specifications sheet for the modules used for the system. (5) Maximum rated output current of the charge controller (if installed) Example: Determine the DC PV power source information needed for the PV power source label based on the following: array consists of twenty-three 200W modules, Imp, Vmp, Voc (at 7 C), and Isc. Figure (1) Rated Maximum Power-Point Current (Imp) Imp = Module Rated Imp Number of Strings in Parallel Imp = 11.05A 1 Imp = 11.05A Figure (F) Labeled. The PV power source must be labeled with the following warning at every junction box and termination point: WARNING ELECTRIC SHOCK HAZARD THE DC CONDUCTORS OF THIS PHOTOVOLTAIC SYSTEM ARE UNGROUNDED AND MAY BE ENERGIZED. Part VI. Marking Direct-Current PV Power Source. A permanent label must be applied by the installer at the PV dc disconnect indicating: (2) Rated Maximum Power-Point Voltage (Vmp) Vmp = Module Vmp Number of Modules per String Vmp = 18.10V 23 = 416V (3) Maximum System Voltage (Voc) PV Voc = Module Voc Table Correction Factor # Modules per String PV Voc = Voc modules PV Voc = 593V (4) Short-Circuit Current (Isc) Isc = Module Isc 1.25 Number of Strings in Parallel Isc = (11.80A 1.25) 1 Isc = 14.75A Mike Holt Enterprises, Inc NEC.CODE ( ) 5

7 Example: What s the rated ac output current for a utility-interactive inverter rated 5 kw at 120/240V supplied by twenty-three dc modules each rated 200W? Inverter Rated ac Output Current = Inverter kw rating/ Nominal ac Voltage Inverter Rated ac Output Current = 5,000W/240V Inverter Rated ac output current = 20.83A at 240V Author s Comment: Panelboards containing ac inverter circuit breakers must be field-marked to indicate the presence of multiple ac power sources [705.12(D)(4)]. Figure Interactive System. The point of connection of the PV system to ac power must be marked with the rated ac output current and nominal operating ac voltage. Figure Identification of Power Sources. (A) Facilities with Stand-Alone Systems. Any building/structure with a stand-alone PV system (not connected to a utility power) must have a permanent plaque placed on the exterior of the building/ structure at a readily visible location that is acceptable to the authority having jurisdiction. The plaque must indicate the location of the stand-alone PV system disconnecting means and that the structure contains a stand-alone electrical power system. (B) Facilities with Utility Power and PV System. Buildings/structures containing both utility power and a PV system must have a permanent plaque placed at the service and PV system ac disconnecting means identifying the location of the other system if not located at the same location. Figure Figure Figure Mike Holt Enterprises, Inc NEC.CODE ( ) 6

8 ARTICLE 705 Interconnected Electric Power Production Sources Introduction to ARTICLE 705 Interconnected Electric Power Production Sources Anytime there s more than one source of power production at the same building or structure, safety issues arise. In cases where a power production source such as a generator is used strictly for standby power, the NEC requires transfer switches and other safety considerations as covered in Articles 700, 701, or 702 depending on whether the standby power is legally required or optional. When interactive electrical power production sources such as wind powered generators, solar photovoltaic systems, or fuel cells are present, there usually isn t a transfer switch. In fact, it can be expected that there will be more than one source of electrical supply connected simultaneously. This can raise many questions regarding how to maintain a satisfactory level of safety when more than one power source is present. Article 705 answers these and other questions related to power sources that operate in parallel with a primary source. Typically, a primary source is the utility supply, but it can be an on-site source instead. Part I. General Scope. Article 705 covers the installation of electric power production sources (photovoltaic, wind, micro-hydro generators, etc) operating in parallel with a primary source(s) of electricity. Figure Note: Primary sources of electricity include a utility supply and on-site electric power sources like photovoltaic or wind powered systems Directory. A permanent plaque or directory denoting all electric power sources on or in the premises must be installed at each service equipment location and all interconnected electric power production sources Point of Connection. (D) Load Side. Where distribution equipment is capable of supplying multiple branch circuits or feeders or both, the interconnecting provisions for the utility-interactive inverter(s) must comply with (D)(1) through (D)(7). (4) Marking. Panelboards containing ac inverter circuit breakers must be field-marked to indicate the presence of multiple ac power sources such as: Figure Figure (7) Inverter Output Connection. Where distribution equipment is capable of supplying multiple branch circuits or feeders, the ac inverter circuit breaker must be located at the opposite end from the input feeder supply conductors. Figure Mike Holt Enterprises, Inc NEC.CODE ( ) 7

9 Where distribution equipment is capable of supplying multiple branch circuits or feeders, a permanent warning label on panelboard is required to warn that the inverter output connection circuit breaker must not be relocated: Figure Figure Figure WARNING INVERTER OUTPUT CONNECTION DO NOT RELOCATE CIRCUIT BREAKER Figure Mike Holt Enterprises, Inc NEC.CODE ( ) 8

10 25% OFF Introducing Mike Holt's Illustrated Guide to Understanding NEC Requirements for SOLAR PHOTOVOLTAIC SYSTEMS This brand new book and DVD program is an insightful guide to the sweeping changes in the NEC as it relates to the installation of PV systems of any size. This program explores the safety aspects of installation and the maintenance of PV systems. If you are a PV installer, Electrician, Inspector or Engineer this book will be an eye opener to the complexity of solar photovoltaic systems and the importance in understanding those NEC Rules that govern their installation. For a limited time you can get your copy for 25% off list price use discount code PVPDF11 NAME TITLE COMPANY ADDRESS CITY STATE ZIP PHONE ADDRESS VISA MASTERCARD DISCOVER AMEX MONEY ORDER CHECK CREDIT CARD # EXP. DATE 3 OR 4 DIGIT SECURITY CODE ON FRONT OF AMEX OR BACK FOR ALL OTHERS 2011 SOLAR PHOTOVOLTAIC SYSTEMS ORDER FORM PRICE QTY TOTAL Book List Price $62 $49.60 $ DVD Program List Price $210 $ $ (includes book & 2 DVDs) SUB-TOTAL $ SALES TAX FLORIDA RESIDENTS ONLY ADD 6% $ Shipping (5% of total price) - Minimum $7.50 $ TOTAL $ Mail form to: 3604 Parkway Blvd., Suite 3, Leesburg, Florida FOR VOLUME DISCOUNTS, PLEASE CALL OUR OFFICE Visit: Call: 888.NEC.CODE ( ) Fax: MIKE HOLT Enterprises, Inc. TM...as for me and my house, we will serve the Lord [Joshua 24:15]