This article continues outlining the procedures for means of providing safe access, pathways and areas considered appropriate for egress to and from photovoltaic (PV) systems. The cell, module, panel and array generally make up a PV system. However, for complete operation, the system must be connected, and pathways must be provided for safe access and egress procedures.
II. BUILDING MOUNTED PHOTOVOLTAIC SYSTEMS
A. All building- or roof-mounted PV systems shall be installed and inspected as specified in this section.
1. Access, Pathways, and Smoke Ventilation. Access and spacing requirements shall be observed to ensure emergency access to the roof, provide pathways for specific areas of the roof, provide for smoke ventilation opportunity areas, and to provide emergency egress from the roof.
2. Exceptions. Exceptions shall be permitted to be granted by the electrical inspector and fire code official (authorities) where access, pathway or ventilation requirements are reduced due to any of the following circumstances:
a. Proximity and type of adjacent exposures.
b. Alternative access opportunities, as from adjoining roofs.
c. Ground access to the roof.
d. Adequate ventilation opportunities below solar arrays.
e. Adequate ventilation opportunities afforded by module set back from other rooftop equipment.
f. Automatic ventilation devices.
g. New technologies, methods, or other innovations that ensure adequate fire department access, pathways, and ventilation opportunities.
3. Designation of ridge, hip and valley does not apply to roofs with 2/12 or less pitch.
4. Measurement Conventions. All roof dimensions shall be measured to centerlines.
5. Roof Access Points. Roof access points shall be defined as areas where ladders are not placed openings (windows or doors) and are located at strong points of building construction and in locations where they will not conflict with overhead obstructions such as trees limbs, wires, signs, etc.
B. Household Systems (One- and Two-Family Dwellings).
1. Access and Pathways
a. Hip Roof Layouts. Modules shall be located in a manner that’s provides one 3-foot-wide clear access pathway from the eave to the ridge of each roof slope where the modules are located. The access pathway shall be located at a structure sound location on the building, such as a bearing wall. EXCEPTION: Where adjoining roof planes provide a 3-foot-wide clear access pathway.
b. Single Ridge Layouts. Modules shall be located in a manner that provides two three-foot wide access pathways from the eave to the ridge on each slope where the modules are located.
c. Hip and Valley Layouts. Modules shall be located no closer than one and one-half to a hip or a valley if modules are to be placed on both sides of a hip or valley. Where modules are located on more than one side of a hip or valley that is of equal length, the modules shall be permitted to be placed directly adjacent to the hip or valley.
2. Ridge Set Back. The modules shall be located no higher than 1 feet below the ridge.
C. Commercial Systems.
1. Definition. Commercial shall be defined as all PV systems installed in any occupancy other than a one- and two-family dwelling.
2. Alternative Requirements. Where the authorities determine the roof configuration is similar to residential (townhouses, condominiums, or single-family attached buildings), the authorities having jurisdiction shall be permitted to make a determination to apply the requirements outlined in Section B above.
3. Access. There shall be a minimum 6-foot-wide clear perimeter around the edges of the roof. Exception: If either access to the building is 250 feet or less, there shall be a minimum 4-foot-wide clear perimeter around the edges of the roof.
4. Pathways. Pathways shall be established as follows:
a. Pathways shall be over structural members.
b. Centerline axis pathways shall be provided in both axes of the roof.
c. Centerline pathways shall run on structural members or over the next closest structural member nearest to the centerlines of the roof.
d. Pathways shall be straight lines not less than four feet clear to skylights, ventilation hatches, and/or roof standpipes. At least a 4-foot clear pathway to the parapet or roof edge shall be provided.
e. Ventilator options between arrays sections shall be (a) a pathway 8 feet or greater in width; (b) a pathway 4 feet or greater in width and bordering on existing roof skylights or ventilation hatches; or (c) a pathway 4 feet or greater in width and bordering 4-foot-by-8-foot “venting cutouts” every 20 feet on alternating sides of the pathway.
Next month, I will discuss circuitry and grounding requirements.
STALLCUP is the CEO of Grayboy Inc., which develops and authors publications for the electrical industry and specializes in classroom training on the National Electrical Code and other standards, including those from OSHA. Contact him at 817.581.2206.