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UL 3741

UL STANDARD FOR SAFETY Photovoltaic Hazard Control

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Organization: UL
Publication Date: 8 December 2020
Status: active
Page Count: 78


Fire fighters (FF) performing operations involving buildings with attached or integrated Photovoltaic (PV) arrays may be exposed to electrical hazards from damaged PV equipment. These requirements provide a means for evaluation of PV Hazard Control components, equipment and systems that provide a reduced level of shock hazard from energized PV system equipment and circuits located within the PV array after the operation of hazard control initiation function(s) where required, such as but not limited to any PV Rapid Shutdown Equipment (PVRSE) or PV Rapid Shutdown Systems (PVRSS) that comply with UL 1741 in the United States and CSA C22.2 No 330 in Canada.

NOTE: Damaged PV equipment in arrays includes damage as a result of fire fighter (FF) interaction as identified throughout this standard and also common PV faults such as PV array ground faults.

This standard is based on the presupposition that the PV array is installed by qualified persons in accordance with the installation instructions and all applicable installation codes and standards. Evaluation to this standard should not replace other requirements addressing the control of power source(s) for the purposes of worker safety during installation or maintenance. Energized circuits can remain in some PV array equipment after any required hazard control initiation function is operated.

NOTE: Requirements for PV arrays addressed in this standard are intended for compliance with the National Electrical Code (NEC), NFPA 70, 2017 and 2020 editions and their requirements for controlling electrical shock hazards inside the array boundary as addressed in NEC section 690.12(B)(2), Rapid Shutdown of PV Systems on Buildings and with the Canadian Electrical Code (CE Code) C22.1. A PVHCS may or may not additionally comply with the 30V in 30 seconds requirements outside the PV array as required in 690.12 (B)(1).

This standard evaluates the hazards associated with potential exposure to DC currents through defined fire fighter (FF) interactions. Alternating current (AC) exposure is limited to not more than 15 Vac, 8A and 240VA for any circuit within the array boundary.

NOTE: This ac voltage limit is aligned with the PVRS requirements in UL 1741 and general electric shock limits.

Equipment and conditions included in scope

These requirements relate to conditions where PV array equipment or assemblies are subjected to a safety analysis considering potential fire fighter (FF) interactions while performing duties during an emergency.

NOTE: These conditions may result in degradation or damage from stresses beyond those covered in existing product safety standards.

The acceptable shock hazard risk established by these requirements is based on defined assumptions related to specific personal protective equipment (PPE) in serviceable condition worn by fire fighters (FF) during structural fire fighting operations on buildings.

NOTE: NFPA 1971 Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting and NFPA 1851 Standard on Selection, Care, and Maintenance of Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting specify the selection, care, and maintenance of fire fighter PPE.

Types of fire fighter (FF) tools and extinguishing agents, including certain water plus foam solutions, during specific fire fighter (FF) tasks are considered in this standard.

NOTE: Specifications for these items are outlined in FF PV Array Interactions, Section 12.3.

Body resistances of adult fire fighters (FF) are defined in this standard to set the criteria by which shock hazards are evaluated.

The materials and methods used to construct the PV array are included in the evaluation. The evaluation to this standard is intended to result in an identified list of PV Hazard Control Equipment (PVHCE) determined to be necessary for the PV hazard control means. The list of PVHCE, and any characteristics of other connected equipment or systems that are essential to maintain the operational integrity of the hazard control function are documented in the PVHCE and / or the PV Hazard Control System (PVHCS) installation instructions in accordance with this standard.

The evaluation is based on a risk assessment of the electrical shock hazards to fire fighters (FF) working in the vicinity of the PV array.

The evaluation addresses the electrical hazard potential of PV array equipment on or integrated into buildings.

Equipment and conditions excluded from scope1

The evaluation does not include equipment where the hazard control systems or functions have been rendered ineffective due to physical damage not specifically addressed in this standard. Examples of physical damage not addressed are the direct exposure of components to fire, smoke, high-pressure hose spray, or major systemic physical damage such as building collapse, destruction or removal of the array.

NOTE: See Section 12.3 for the fire fighter (FF) interactions, including handheld hose lines, specifically addressed by this standard. Firefighting Monitors are controllable high capacity water jets that operate at higher pressures and volumes which can result in mechanical or structural damage to equipment and are therefore excluded from the scope of this standard.

1 Additional installation requirements addressing rapid shutdown of PV system circuits can be found in the National Electrical Code (NEC), NFPA 70, Section 690.12, Rapid Shutdown of PV Systems on Buildings, and the Canadian Electrical Code (CE Code) C22.1 64-218 requirements.

While this standard accounts for fire fighters (FF) wearing new or serviceable used PPE, it does not include consideration for any damage to PPE that occurred prior to fire fighter (FF) interaction with the PV array.

NOTE: Standard operating procedures is to replace damaged fire fighting PPE.

The use of extinguishing agents not specified in this standard, such as seawater or high foam concentrations, are not included in the evaluation.

NOTE: The requirements and resistance data in this standard are based on expected practices and are considered to provide information sufficient for performing a safety analysis.

These requirements do not replace any electrical safe work practices for persons installing, servicing or maintaining the PV system.

Though all components, equipment, and systems that could be used to construct the PV array are considered in the evaluation, not all array equipment and components are required to be identified to perform the PV hazard control function, or be specifically addressed in the installation instructions for the purposes of this standard.

NOTE: Examples for parts that are not required to be identified are parts such as nuts, bolts and other passive components not used directly to provide hazard reduction, as determined by the analysis in Section 12.

These requirements do not address any electrical shock hazards not covered by this standard or other hazards that PV arrays may present such as slip, trip or fall hazards.

This standard is not intended to address fire fighter (FF) interactions involving PV array equipment not installed on a building.

Document History

UL 3741
December 8, 2020
UL STANDARD FOR SAFETY Photovoltaic Hazard Control
Introduction Fire fighters (FF) performing operations involving buildings with attached or integrated Photovoltaic (PV) arrays may be exposed to electrical hazards from damaged PV equipment. These...