1、UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULUNDERWRITERS LABORATORIES INC. CERTIFICATION REQUIREMENT DECISIONThis Certification Requirement Decision is prepared by UL LLC. It is normative for the applicable ULProduct Certification Program(
2、s); however, it is currently not part of the UL Standard(s) referencedbelow.Product Category (CCN): QIKAStandard Number: UL 3703Standard Title: Standard for Solar TrackersEdition Date: October 8, 2015Edition Number: 1Section / Paragraph Reference: 6 Mechanical Assembly (reference only), 16 Bondingfo
3、r Grounding and PERFORMANCESubject: Add additional requirements for spring clip module securement and pinnedjoints in the bonding path.DECISION:6 Mechanical Assembly6.2 A tracker shall be assembled so that it is not adversely affected by the vibration of normal operation.16 Bonding for Grounding16.6
4、 A connection in the bonding path shall be by a positive means, such as by a clamp, a rivet, a boltedor screwed connection, or by welding, soldering, or brazing with materials having a softening or meltingpoint greater than 455C (850F). The bonding connection shall penetrate nonconductive coatings,
5、suchas paint or vitreous enamel. Ferrous metal parts shall comply with Protection Against Corrosion, Section6. Revolute or pinned joints in the bonding path shall be assessed for positive means according to theSection 62A, Cyclic Load Test.PERFORMANCE62A Cyclic Loading Test62A.1 The provisions of th
6、is section establish a minimum level of fatigue resistance for the structure (see6.2) and bonding path (see 16.6), for units that include revolute or pinned joints.62A.2 The tracking system, composed of the module, module mounting means and supporting structuralmembers shall resist low-cycle fatigue
7、 without a loss in mechanical integrity or loss of bonding path circuitcontinuity, when subjected to a minimum of 15,000 cycles of the alternating load defined in this section.62A.2.1 Mechanical Integrity: The Tracker shall not exhibit evidence of structural or mechanical failure,visual permanent de
8、formation that may adversely affect system safety or compliance, and for any PVmodule securement means including top-down clamps, there shall not be any shifting/movement.62A.2.1.1 The load applied shall be based upon the summed tributary area of the modules defining arepeatable unit, including all
9、functional interfaces of the racking system.62A.2.1.2 If the modules are stowed within 10 of flat/horizontal during high wind speeds (greater than50 mph), the applied loading shall be 10 psf minimum in the negative (downward) direction and 5 psf inthe positive (upward) direction.UL COPYRIGHTED MATER
10、IAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM UL62A.2.1.3 If the modules are not stowed within 10 of flat/horizontal during high wind speeds, the appliedloading shall be 20 psf in the negative (downward) direction and 10 psf in the positive (upward) direction.Exc
11、eption: Other applied loads (e.g., originating from wind tunnel testing or computational fluid dynamicsmodeling) are allowed if they are clearly stated on the manufacturers technical datasheet and installationinstructions.62A.2.1.4 The load(s) shall be applied as point loads at the center of the mod
12、ule(s), or as distributedload(s) across the modules and the load shall vary cyclically from positive to negative at a frequency notgreater than 2 HZ.62A.2.2 Bonding Path Continuity. Bonding paths shall pass the Bonding Path Resistance Test (below) atthe start and completion and not exhibit loss of c
13、ircuit continuity between readings.62A.2.2.1 The Section 42 Bonding Path Resistance Test shall be measured within the first 100 cycles andwithin the last 100 cycles of the applied cyclic load.62A.2.2.3 Between resistance measurements, the bonding path is to be monitored for loss of circuitcontinuity
14、 using an instrument with a sampling rate at least 20x faster than the maximum mechanicalcyclic rate. If the bonding resistance measurement includes an averaging function, the averaging windowshall be minimum 20 times smaller than the fastest mechanical cycling rate.RATIONALE FOR DECISION:Regarding
15、mechanical integrity, UL 3703 refers to UL 2703 for module mounting clamps. UL 2703,Section 6 does not preclude the use of spring-style clamping means for modules and 6.3 makes clear theneed for adequate structural integrity of the clamping means to retain the modules under cyclic load. UL2703 speci
16、fically addresses compliance for mechanical integrity through construction means withconventional threaded fasteners, rivets, and fusion welding. For other designs, a performance-basedassessment is needed to establish suitability. The approach applied in this CRD is a low-cycle fatigue test.It is si
17、milar in its 10,000 cycle baseline to the Cyclic Load test described in IEEE 1262-1995 but is modifiedfor actual load value to drive consistency with the minimum design loads specified in UL 2703 Sec 21.4and incorporates a minimum safety factor of 1.5 to the cycle count. The value of applied load is
18、 differentfor trackers that stow during high speed wind events and aligns to UL 2703 in its minimum static loadrequirements for trackers that do not perform a stow function. It is recognized that the predominance ofComputational Fluid Dynamics modeling and boundary-layer wind tunnel testing means th
19、at themanufacturer may wish to apply different loads during this test and that is allowed provided that the loadsused are clearly stated in their technical documentation.To assess the suitability of a pinned or revolute joint present in the bonding path, the key issue is thevalidation of “positive m
20、eans” as referred to in UL 3703 Section 16.6 and present in UL 2703 Section 9.5.The daily motion of a tracker and its exposure to wind leads to potential fatigue-induced degradation ofthe bonding path, with a potential failure mode leading to a shock hazard. The cyclic load test describedabove is co
21、nsidered a suitable means to assess low cycle fatigue degradation of the bonding path whena resistance measurement at the start and end of the test is below 0.1 ohm and there is no loss of bondingcircuit continuity evident through the course of the test.Copyright 2017 UL LLCUL LLC, in performing its
22、 functions in accordance with its objectives, does not guarantee or warrant thecorrectness of Certification Requirement Decisions it may issue or that they will be recognized or adoptedby anyone. Certification Requirement Decisions are the opinion of UL LLC. in practically applying therequirements o
23、f the standard. They do not represent formal interpretations of the standard underSTANDARD NUMBER: UL 3703 -2-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULAmerican National Standards Institute (ANSI) processes. UL LLC shall not be responsib
24、le to anyone forthe use of or reliance upon Certification Requirement Decisions by anyone. UL LLC shall not incur anyobligation or liability for damages, including consequential damages, arising out of or in connection withthe use or reliance upon Certification Requirement Decisions. The electronic
25、version of the CertificationRequirement Decision is the current version and previously printed copies may be outdated.This document is published as a service to ULs certification customersSTANDARD NUMBER: UL 3703 -3-UL COPYRIGHTED MATERIAL NOT AUTHORIZED FOR FURTHER REPRODUCTION ORDISTRIBUTION WITHOUT PERMISSION FROM ULSTANDARD NUMBER: UL 3703 -4-No Text on This Page
