structural evaluation of orions belt … evaluation of orions belt ballast system ... orion solar...

STRUCTURAL EVALUATION OF ORIONS BELT BALLAST SYSTEM

for State of California

Prepared For: Orion Solar Racking

November 24 2014

The scope of this report focuses on providing a structural evaluation of the push/pull static load test of the Orions Belt ballast systemmanufactured by Orion Solar Racking. Static load tests were conducted by National Technical Systems. Structural adequacy of the existing building structure/framing is excluded in this report. The structural performance of the railing has been verified to be in compliance with the requirements of the 2013 California Building Code and SEAOC PV2 under prescribed wind in the state of California. Static loads test results verified that the connections of the ballast werestructurally sufficient to resist the wind loads imposed on the ballast system.

Orion Solar Racking 2917 Vail Ave. Commerce, CA 90040

RE: Sunstrong Structural Evaluation Report of Orion s Belt Ballast System

Section

Memo Summary

Wind Analysis

Design Criteria

Design Code References

SEAOC PV-2

Analysis Results

Conclusion . .

Figure 1:

Select Portion from Figure 29.9-1 (SEAOC PV-2)

SEAOC PV-2 The methodology from SEAOC PV-2 offers a more case specific approach in deriving the wind loads experienced in low-profile photovoltaic arrays on flat roof low-rise buildings. In doing so, section 29.9 (See Figure 1) was added to ASCE 7-10 along with additional tables and testing procedures. Excel spread sheets specifically programmed to follow the procedures outlined in SEAOC PV-2 were utilized to obtain the working wind loads for the Orions Belt ballast system. The results from these spread sheets are attached in this report.

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November 24 2014

WIND ANALYSIS Based on ASCE 7-10 and SEAOC PV-2, photovoltaic arrays will experience different wind pressures based on a number of factors such as building dimensions, tilt angle of arrays, wind exposure category, location of arrays on roof, etc (See Figure 2). For this report conservative design parameters were considered in evaluating the adequacy of the ballast system to resist the resulting wind pressures. Figure 2:

Select Portion from Figure 29.9-1 (SEAOC PV-2) Worst case loading conditions were based on the following two load combinations per section 2.4 of ASCE 7-10:

1. D + 0.6W

2. 0.6D + 0.6W Where D is the dead load of the panels and racking equipment and W is the wind uplift loads. Since photovoltaic modules were not intended to be walked on, it is structurally acceptable to disregard load combinations with the live load component. Based on these two combinations, the governing load combination that results in the largest effect from wind uplift loads is the first one. However, for additional level of safety, 100% of the wind load was considered when comparing to the allowable load of the ballast system.

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DESIGN CRITERIA The following parameters were considered in determining the values of the wind uplift loads for the ballast system:

Maximum Building Height Considered = 30 ft Exposure Categories Considered: C Wind Pressure Based on SEAOC PV-2 Maximum Tilt of Modules: 10 degrees Maximum Wind Speed Considered: 130 mph Minimum Edge Distance of Arrays: 4 ft Ballast System Considered with Load Sharing (50 %) Load reduction from Tunnel Test & Load Sharing: 0 % Corner Zones (Zone 3) Pressures Only Considered Panel Width Considered: 5.5 ft Panel Chord Length Considered: 3.3 ft Coefficient of Friction = 0.4 Yield Safety Factor = 1.65 (per ADM) Adequacy of Connections Based on Push/Pull Tests (Attached)

DESIGN CODE REFERENCES The following engineering references were considered in determining the values of the wind load conditions and material properties of the aluminum railing:

IBC 2012 / CALIFORNIA BUILDING CODE 2013 ASCE 7-10 / SEAOC PV-2 2012 Aluminum Design Manuel 2010

November 24 2014

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Figure 3:

Vertical Wind Uplift Calc According to SEAOC PV-2

Orions Belt Ballast System Structural Report – CALIFORNIA November 24 2014

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CONCLUSION

Based on the results from the Excel spreadsheet calculations for ballast wind loads per SEAOC PV-2 (See Figure 3) the following adequacy check was calculated:

Since the allowable uplift capacity of the ballast tilt leg exceeds the value of the worst case uplift load calculated from the SEAOC PV-3 analysis, the Orions Belt ballast system in considered structurally sufficient to be used on flat roof low-rise buildings according to the parameters indicated in this report.

Please feel free to contact us with any questions or concerns regarding the information provided in this report.

Respectfully Submitted,

PHONG “PAUL" TRUONG, PEPresident

ATTACHMENTS

Orions Belt Ballast System Structural Report – CA November 24 2014

5

STRUCTURAL ENGINEERS ASSOCIATION OF CALIFORNIA

WIND DESIGN FOR LOW-PROFILE SOLAR PHOTOVOLTAIC ARRAYS ON FLAT ROOFS

Prepared by SEAOC Solar Photovoltaic Systems Committee Report SEAOC PV2-2012 August 2012


Wind Design for Low-Profile Solar Photovoltaic Arrays on Flat Roofs Report SEAOC PV2-2012

August 2012 Page ii

Board of Directors, 2011-2012

Douglas Hohbach, President*Jim Amundson, President Elect* Janah Risha, Secretary Bradley Lowe, Treasurer* Stephen Pelham, Past President* Don Schinske, Executive Director*

*Executive Committee

Kelly Cobeen, Director Jeff Crosier, Director* Diane Gould, Director Grace Kang, Director Zubaid Karim, Director Joe LaBrie, Director Peter Lee, Director Jeffrey Marchant, Director Michael West, Director

Disclaimer

Documents produced by the Structural Engineers Association of California (SEAOC) are published as part of our association’s educational program. While the information presented in the document is believed to be correct, neither SEAOC nor its Board, committees, writers, editors, or individuals who have contributed to this document make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, findings, conclusions, or recommendations expressed herein. The material presented in this document should not be used or relied upon for any specific application without competent examination and verification of its accuracy, suitability, and applicability by qualified professionals. Users of information from this document assume all liability arising from such use.

Structural Engineers Association of California © 2012 SEAOC All rights reserved. This document or any part thereof may not be reproduced in any form without the written permission of the Structural Engineers Association of California.

STRUCTURAL ENGINEERS ASSOCIATION OF CALIFORNIA 1020 12th Street, Suite 303

Sacramento, CA 95814 Phone: (916) 447-1198

Fax: (916) 444-1501 Email: [email protected] http://www.seaoc.org



August 2012 Page iii

Wind Design for Low-Profile Solar Photovoltaic Arrays on Flat Roofs

These guidelines were written by the SEAOC Solar Photovoltaic Systems Committee, a subcommittee of the SEAOC Wind Committee.

SEAOC Solar Photovoltaic Systems Committee

Voting Members Ron LaPlante (Chair) DSA Joe Maffei (Vice Chair) Rutherford & Chekene Joe Cain, SolarCity James S. Lai, S.E. Ken Luttrell, CYS Structural Engineering Shane Noel, KPFF Consulting Engineers, Inc. G.R. Searer, Wiss, Janney, Elstner Associates, Inc. Norm Scheel, Norman Scheel Structural Engineer Mason Walters, Forell/Elsesser Engineers Rob Ward, SunLink

Associate MembersDavid Banks, Cermak Peterka, and Peterson Steve Bauer, Unirac Geoff Bomba, Forell/Elsesser Engineers Pete Fischer, DSA Ajay Friesen, SunPower Mark Gies, PanelClaw Rick Hanson, SolarCity John Harvey, Buehler & Buehler Gregory Kopp, University of Western Ontario Jonathan Lam, Los Angeles County Coleen O’Brien, BEW Engineers Tim Reinhold, Institute for Business & Home Safety Adam Saidel, Unirac Don Scott, PCS Structural Solutions Karl Telleen, Rutherford & Chekene Philip Yin, City of Long Beach Osama Younan, City of Los Angeles

SEAOC Wind Committee 2011-2012

Ken Luttrell (Chair), CYS Structural EngineeringStephen Kerr, Josephson-Werdowatz & Associates, Inc. Scott Markle, Los Angeles World Airports Brent Nuttall, Nabih Youssef & Associates James S. Lai, S.E.

Dick Phillips, S.E.James Sadler, Jasco Pacific Inc Norm Scheel, Norman Scheel Structural Engineer G.R. Searer, Wiss, Janney, Elstner Associates, Inc.



August 2012 Page iv

Preface and Acknowledgements This document was developed by the Structural Engineering Association of California’s (SEAOC) Solar Photovoltaic Systems Committee (PV committee), a subcommittee of the SEAOC Wind Committee. The PV committee was formed in September 2011 on the initiative of building code officials, structural engineers, and solar industry representatives. The principal goal in forming the committee was to address the lack of clarity and specific requirements in applying structural building code provisions to solar photovoltaic systems. The committee began its work with discussions that led to identi-fying (a) the types PV support systems that were most prevalent and most in need of clarification regarding their structural design, and (b) the key structural engineering issues in the design of such arrays.

The structural engineering issues identified in these dis-cussions included:

The question of acceptability of unattached rooftop solar arrays in relation to seismic design requirements and objectives;

The question of applicability of component and cladding wind loads to many solar array types;

Recommendations and necessary requirements for wind-tunnel testing of solar arrays (testing which is typically done for a type of PV support system rather than a specific site location and installation);

The question of applicability of code minimum wind loads to solar arrays designed based on wind-tunnel test results; and

The potential development of code wind loads specifically applicable to solar arrays.

While there is a growth of solar installations of several types, including residential and ground-mounted installations, many of the engineering issues identified were most relevant to low-profile photovoltaic installations on commercial flat roofs. The committee chose to direct its initial efforts on such systems, considering both seismic and wind structural design issues. The work of the committee then focused on the production of two reports: Report PV1-2012, addressing seismic-structural design, and Report PV2-2012, addressing wind design. Joe Maffei directed the development of the PV1 report and Ron LaPlante directed the development of the PV2 report. It is our hope and that of SEAOC that these documents

provide valuable information to ASCE-7 and other standards writing groups.

The PV committee intends to continue its work on the timely issues related to the structural design of solar installations. Future activities may include updates to the PV1 and PV2 reports and new efforts addressing quality assurance and roof live load issues. Comments on the documents can be sent by e-mail to [email protected] and [email protected].

We would like to express our appreciation to the SEAOC Board, the SEAOC SSC committee, chaired by Kevin Moore, and the SEAOC Wind Committee, chaired by Ken Lutrell, who oversaw and supported the work of the PV Committee. In particular for Report PV2, we would like to thank Dr. David Banks from Cermak Peterka Petersen (CPP) and Dr. Gregory Kopp from The University of Western Ontario for their invaluable contribution on the development of the wind loads figure from wind tunnel test data. Also, thanks to David Carpenter and David Banks from CPP for use of CPP figures and write-up on the wind flow characteristics on flat roofs. Special thanks to Karl Telleen from Rutherford & Chekene and Adam Saidel from Unirac for their efforts in developing the example problem in the Appendix and to Paul Rooney from DSA for drawing Figure 29.9-1 countless times.

We also are grateful to the SEAOC Seismology Committee, chaired by Geoff Bomba, for their thoughtful review of the PV1 report; their comments improved the document. Finally, we express our gratitude and appreciation to the members of the PV Committee, who dedicated their time—in more than twenty online meetings and in reviews of numerous drafts—to shaping the two reports that are now completed. The committee members brought diverse backgrounds and perspectives to the discussion, and the resulting works reflect a range of knowledge and understanding that is much greater than could come from any one individual. In directing this effort, we deeply grateful for all that we have learned, and for the good will and dedication of so many contributors who came together to produce these documents.

Sincerely, Ron LaPlante and Joe Maffei August 2012


Wind Design for Low-Profile Solar Photovoltaic Arrays on Flat Roofs August 2012 Report SEAOC PV2-2012 Page 5

Table of Contents Section page Disclaimer 2 Committee Members 3 Preface and Acknowledgements 4 1. Abstract 6 2. Introduction 6 3. Prescriptive GCrn Values for Solar Arrays Mounted on Flat Roofs 6

3.1. Proposed Code Changes 6 3.2. Commentary 10

3.2.1. Procedure to Using Wind Load Figure 10 3.2.2. Wind Flow Characteristics on Roofs 10 3.2.3. Development of Wind Loading Figure Based on ASCE 7 11

3.2.3.1. General 11 3.2.3.2. Roof Wind Zones 12 3.2.3.3. Building Edge and Parapet Effects 12 3.2.3.4. Nominal Net Pressure Coefficient, (GCrn)nom 13 3.2.3.5. Shielding within an Array 13 3.2.3.6. Design of Roof Supporting Solar Array 14

4. Effective Wind Area 14 5. Wind Tunnel Test per ASCE 7 15 References 17 Appendix A: Example Calculation



1. Abstract: The design wind loads for solar photovoltaic arrays on flat roof low-rise buildings are not covered by the prescriptive methods contained in ASCE 7 Minimum Design Loads for Buildings and Other Structures. This report describes the wind flow characteristics of rooftop solar photovoltaic (PV) arrays and the development of this information into a figure similar to that used in the prescriptive methods contained in ASCE 7 using the same design methodology. The report also addresses requirements for wind tunnel studies, effective wind area computation, and the wind loads on the roof itself.

2. Introduction: In the absence of detailed guidance from ASCE 7 for wind loads on photovoltaic arrays on flat roof low-rise buildings, designers often attempt to use a hybrid approach of the ASCE 7 components and cladding tables for enclosed buildings and main force resisting system tables for open structures, or they use the wind tunnel procedure of ASCE 7. The hybrid approach can lead to unconservative results, particularly when considering the size of the edge and corner roof zones. The wind tunnel procedure can be costly and time consuming, particularly for small or single-use projects. Furthermore, there are no code-based index values for the wind pressure coefficient GCrn with which to compare those developed from wind tunnel studies. The solar industry and code enforcement agencies are in need of a prescriptive method similar to that provided in ASCE 7. Recognizing that the solar industry and code enforcement agencies are in need of these design provisions, SEAOC formed the Solar PV committee to develop this report and provide these interim guidelines. This report describes the wind flow characteristics for solar photovoltaic panels on flat roofs and provides a figure similar to that used in the prescriptive methods contained in ASCE 7, using the same design methodology to generate GCrn values that are consistent with the design equations contained in ASCE 7. The intent is for this method to be used with either ASCE 7-05 or ASCE 7-10; where necessary, this report provides a distinction in applicability between the two standards. ICC AC 428 “Acceptance Criteria for Modular Framing Systems Used to Support Photovoltaic (PV) Modules” may be used to determine the wind loads for freestanding ground-mounted systems and flush-mounted systems. Freestanding ground-mounted systems are stand-alone systems and may use the open buildings prescriptive method contained in ASCE 7; this procedure is not applicable to rooftop installations on buildings. Flush-mounted systems are installed parallel to the roof surface of a building, within 2 to 10 inches of the roof surface, and may use the enclosed building components and cladding prescriptive method contained in ASCE 7.

The focus of this report is on low-profile photovoltaic arrays on flat or low-slope roofs of low-rise buildings, and not on ground-mounted systems or roof-mounted systems on other roof shapes (e.g. hip, gable, saw-tooth, etc.). Proposed changes to ASCE 7-10 include: adding Section 29.9 to address solar arrays on flat roofs modifying Table 29.1-1 to include solar arrays adding Figure 29.9-1 to determine pressure coefficients for

solar arrays adding a definition of Effective Wind Area for solar arrays adding Section 31.6 to address wind tunnel testing of solar

arrays

Throughout this document, where ASCE 7-10 changes are being proposed, the existing unmodified language in ASCE 7-10 is italicized, whereas the proposed changes are italicized and underlined. Following each proposed code change, the report typically includes a commentary providing background information.

3. Prescriptive GCrn Values for Solar Arrays Mounted on Flat Roofs

This section presents code language and a figure similar to that used in the prescriptive methods contained in ASCE 7 for wind loads on low-profile rooftop solar photovoltaic arrays installed on flat roofs.

3.1. Proposed Code Changes The following code language and figure provide an ASCE 7 based prescriptive method for determining the GCrn values and wind loads for solar photovoltaic panels installed on flat roofs. This method is applicable to the conditions illustrated in the figure with corresponding limitations. No extrapolation beyond the limitations shown shall be made. The equations and methodology in ASCE 7 for determining the velocity pressures and associated site coefficients shall be used with the GCrn values shown herein. The proposed code language uses the term “panel” to mean a planar assembly of solar photovoltaic (PV) modules. The term PV “modules” refers to manufactured, environmentally protected units of solar cells that form the basic unit of solar photovoltaic arrays. This terminology is consistent with Section 690 of the 2011 National Electrical Code. The following is the proposed code language corresponding to ASCE 7-10. The figure references both ASCE 7-05 and ASCE 7-10 sections where applicable.



29.9 Rooftop Solar Arrays for Buildings with ≤ 7°

The design wind pressure for rooftop solar arrays located on buildings with a slope ≤7 degrees and a mean roof height h ≤ 60 ft (18.3 m), or where mean roof height h > 60 ft (18.3 m) provided that the building is wider than it is tall, shall be determined by the following formula:

p = qh (GCrn) (lb/ft2) (N/m2) (29.9-1)

where

qh = velocity pressure evaluated at mean roof height of the building

(GCrn) = combined net pressure coefficient for solar panels, determined from Figure 29.9-1

The following are the proposed changes (indicated via underline) to Table 29.1-1 of ASCE 7-10:

Table 29.1-1 Steps to Determine Wind Loads on MWFRS Rooftop Equipment and Other Structures

Step 1: Determine risk category of building or other

structure, see Table 1.5-1 Step 2: Determine the basic wind speed, V, for applicable

risk category, see Figure 26.5-1A, B or C Step 3: Determine wind load parameters:

Wind directionality factor, Kd, see Section 26.6 and Table 26.6-1

Exposure category B, C or D, see Section 26.7

Topographic factor, Kzt, see Section 26.8 and Figure 26.8-1

Gust Effect Factor, G, see Section 26.9 Step 4: Determine velocity pressure exposure coefficient,

Kz or Kh, see Table 29.3-1 Step 5: Determine velocity pressure qz or qh, see Eq

29.3-1 Step 6: Determine force Coefficient, Ci:

Solid freestanding signs or solid freestanding walls, Fig. 29.4-1

Chimney, tanks, rooftop equipment Fig. 29.5-1

Open signs, lattice frameworks Fig. 29.5-2 Trussed towers Fig. 29.5-3 Rooftop solar arrays Fig. 29.9-1

Step 7: Calculate wind force, F, or pressure , p: Eq. 29.4-1 for signs and walls Eq. 29.5-2 and Eq. 29.5-3 for rooftop

structures and equipment Eq. 29.5-1 for other structures Eq. 29.9-1 for rooftop solar arrays

Test Report No. PR032558 Revision 1, October 29, 2014

Page 1 of 52

www.nts.com

This report and the information contained herein represents the results of testing of only those articles/products identified in this document and selected by the client. The tests were performed to specifications and/or procedures approved by the client. National Technical Systems (“NTS”) makes no representations expressed or implied that such testing fully demonstrates efficiency, performance, reliability, or any other characteristic of the articles being tested, or similar products. This report should not be relied upon as an endorsement or certification by NTS of the equipment tested, nor does it present any statement whatsoever as to the merchantability or fitness of the test article or similar products for a particular purpose. This document shall not be reproduced except in full without written approval from NTS.

National Technical Systems Main: 714-879-6110 1536 East Valencia Drive Fax: 714-879-6117 Fullerton, California 92831

REVISION 1 October 29, 2014 Orion Solar Racking Inc. 2917 Vail Avenue Commerce, California 90040 Purchase Order Number: P768

A. TESTS: 1002-Torque vs Module, 1001-A Push and 1001-B Pull B. TEST ITEMS: See Page 2 for Test Item Identification C. SPECIFICATIONS: 1. Orion Solar Racking Document M2 Concept Testing,

File 1001, 09/30/14 2. ANSI NCSL Z540-1 3. ISO 17025:2005

D. RESULTS:

This is to certify that the Brackets were subjected to the referenced tests in accordance with the above specifications. While conducting the 1001-B Pull Test on S/N NTS-7, the nut attaching the Bracket to the Instron fixture stripped (see NOD-1). Visual examination showed no further evidence of physical damage resulting from the tests. The Brackets were returned to Orion Solar Racking Inc. for post tests and final evaluation. Test data, an equipment list, and photographs are attached.

R.M. “Rick” Clemens, Betty Matteson, Preparer Quality Assurance Manager

Connor Smith, Program Manager

Test Report No. PR032558

Revision 1, October 29, 2014

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REVISIONS

Revision Reason for Revision Date

NR 1

Initial Release Replaced data sheet with data sheet corrected from 0.2 inches deflection to 0.02 inches, Page 5. Replaced plot with plot legend reversed axis definitions corrected, Page 9.

10/27/14

10/29/14



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TEST ITEM IDENTIFICATION

Quantity Part Number Serial Number

Three (3) Front Brackets Orions Belt NTS 1, NTS 3 and NTS 16

One (1) Back Bracket Orions Belt NTS 2

Six (6) High Brackets Orions Belt NTS 4, NTS 6, NTS 8, NTS 10, NTS 12 and NTS 14

Six (6) Low Brackets Orions Belt NTS 5, NTS 7, NTS 9, NTS 11, NTS 13 and NTS 15



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EQUIPMENT LIST Description Apparatus Calibration 1002-TORQUE VS MODULE CDI Torque Wrench 12 months 10/22/14 – 10/24/14 Model 2401C13 Due 12/27/14 S/N 04100060487 Range: 24 to 240 in. lbs Accuracy: ±4% NTS Control No. FL 6016 Cole-Parmer Meter 24 months (Hygrometer) Due 5/1/16 Model 03313-86 S/N 101952506 Accuracy: ±2°F/3% RH Range: -58 to 122 F/25 to 95% RH NTS Control No. FL 2863 China Dial Indicator 12 months Model 0 to 1 inch Due 12/20/14 S/N 5743 Accuracy: ±0.001 inch Range: 0 to 1 inch NTS Control No. FL-2446 1001-A PUSH AND Cole-Parmer 24 months 1001-B PULL Thermohygrometer Due 4/11/16 10/22/14 – 10/23/14 Model 03313-86 S/N 122180743 Range: 25 to 95% RH 32° to 122°F Accuracy: ±2% RH, ±2°F NTS Control No. FL 6654 PRO 3600/Industrial Not Required Digital Protractor Model PRO 3600 S/N 09090264 Range: 0 to 360º Accuracy: ±0.1º NTS Control No. FL 5694 Instron Corporation 12 months Universal Due 10/10/15 Test Machine Model 4204 S/N 3167 Range: 0-10,000 lbs

Accuracy: ±1% NTS Control No. FL 2600



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EQUIPMENT LIST Description Apparatus Calibration 1001-A PUSH AND Schlumberger Ind. LVDT Not Required 1001-B PULL Model none, S/N CH 2 10/22/14 – 10/23/14 Range: Mfg Accuracy: 0.18% NTS Control No. FL 3993 Schlumberger Signal Not Required Conditioner Model OD3, S/N none Range: N/A Accuracy: MFG NTS Control No. FL 5853



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1002-Torque vs Module Setup

1002-Torque vs Module Setup



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1002-Torque vs Module S/N NTS 1 - Setup

1002-Torque vs Module S/N NTS 1 – Post Test



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1002-Torque vs Module S/N NTS 3 – Pre-Test




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1002-Torque vs Module S/N NTS 16 – Setup



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1001-A Push and 1001-B Pull Setup



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1001-A Push and 1001-B Pull S/N NTS 4 – Post Test



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1001-A Push and 1001-B Pull S/N NTS 7 – NOD-1



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32.00

11.06(Varies with tilt angle) 6.21

10.00°

24.00(spacing varies with tilt angle)

64.00(width dependent on PV Module dimensions)

6.27 (Supports multiple 6 x 4 x 16 inch ballast blocks)

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C. SchwartzmanDRAWN BY DATE

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Orion Solar Racking2917 Vail Ave. Commerce, CA 90040TEL: (310) 409-4616Copyright © 2011 Orion Racking.orionsolarracking.com

MATERIAL

DESCRIPTION

SIZE

APART NO. REV

NTSSHEET 1 OF 1 DO NOT SCALE DRAWING

11/24/14

Orion Ballasted System

Al 5052 with 304 Stainless Steel Hardware