November 17, 2022

Comments on Proposed Changes to UL 9540

See eight instances where SEAC's ESS Standards working group proposed modifications to the second edition of UL 9540.
Battery room in power plant

The UL Energy Storage Systems and Equipment Standards Technical Panel invites participating industry stakeholders to comment on UL 9540, the Standard for Safety for Energy Storage Systems and Equipment, as the panel develops new editions of the standard. UL published the second edition of UL 9540 in February 2020. During a review period that opened in April 2022, industry stakeholders submitted 165 comments with suggested revisions.

The SEAC Energy Storage Systems (ESS) Standards working group reviews stakeholder comments. The group issues modified revisions as needed and provides an explanatory response to inform the standards technical panel, the commenter, and the public about its handling of comments when modifications are proposed. Below is a list of eight instances where the ESS Standards working group has responded with modifications.

UL has grouped comments by topic, such as marking criteria, capacity limits, explosion protection, noise levels, and more. All modified revisions issued by the ESS Standards working group address Topic 1: Revisions to Marking Criteria and Inclusion of AC and DC ESS Concepts. Three of the modified revisions address the glossary in UL 9540 Section 6. Five modified revisions address markings in Section 41.

To view the full text of UL 9540, first create an account at the UL Standards Sales Site. Enter your contact information with a username and password to get started. Next visit the UL 9540 purchase page or search “9540” in the UL Standards catalog. Underneath the Purchase Options button, click the Digital View – English button for a free view of UL 9540. UL also provides free access to the UL 9540 text in French.

Visit the SEAC working groups page for more information about the ESS Standards working group, and view the SEAC events calendar for details about the ESS Standards working group’s next online meeting.

Section of UL 9540: 6.5A
Comment Details: Comment #4 and #18, Topic #1
Proposal Language: 6.5A DWELLING UNIT – See the definition for “dwelling unit” in Article 100, Definitions, of NFPA 70
SEAC WG Modified Revision: 6.5A DWELLING UNIT – See the definition for “dwelling unit” in Article 100 Chapter 3, Definitions, of NFPA 70 855, in the Definitions section of CAN/CSA C22.1, in the General Definitions, Section 202 of ICC IFC, and in Chapter 2, Definitions of ICC IRC
SEAC WG Response: Accepting the comment in principle, but with changes in the proposal wording. Revisions will be proposed in a UL 9540 Recirculation Work Area in CSDS.

Section of UL 9540: 6.22
Comment Details: Comment #5, Topic #1
Proposal Language: 6.22 NON-RESIDENTIAL USE – Equipment suitable for use on or in structures other than residential dwellings. ESS installations for use in commercial, industrial or utility owned locations.
Comment Suggested Revision: 6.22 NON-RESIDENTIAL USE – Equipment suitable for use on or in structures other than one-family dwellings, two-family dwellings or multi-family dwellings as defined in the NFPA 70, or residential occupancies as defined in the CSA C22.1 residential dwellings.
SEAC WG Modified Revision: 6.22 NON-RESIDENTIAL USE – Equipment suitable for use on or in structures other than residential use those defined in 6.24. dwellings.
SEAC WG Response: Accepting the comment in principle, but with changes in the proposal wording. Revisions will be proposed in a UL 9540 Recirculation Work Area in CSDS.

Section of UL 9540: 6.24
Comment Details: Comment #5, Topic #1
Proposal Language: 6.24 RESIDENTIAL USE – Equipment suitable for use on or in one or two family structures and townhouses and on or in individual units of multi-family dwellings. In accordance with this Standard, intended for use in one or two family homes and townhomes and multi-family dwellings.
Comment Suggested Revision: 6.24 RESIDENTIAL USE – Equipment suitable for use on or in structures other than one-family,  dwellings, two-family,  dwellings or multi-family dwellings and on or in individual units of two-family or multifamily dwellings as defined in the NFPA 70, or residential occupancies as defined in the CSA C22.1.
SEAC WG Modified Revision: 6.24 RESIDENTIAL USE – Equipment suitable for use on or in detached one- and two-family dwellings and townhouses. one or two family structures and townhouses and on or in individual units of multi-family dwellings.
SEAC WG Response: Accepting the comment in principle, but with changes in the proposal wording. Revisions will be proposed in a UL 9540 Recirculation Work Area in CSDS.

Section of UL 9540: 41.3e)2)
Comment Details: Comment #8, Topic #1
Proposal Language: e) Residential ESS on or in a dwelling unit shall be marked as follows: 1) If meeting the requirements of 23.2.2: “Suitable for Use in Residential Habitable Spaces”; or 2) If meeting the requirements of 23.2.3 “Suitable for Use in Residential Non-Habitable Spaces”; and
Comment Suggested Revision: g) Systems meeting the cell level performance criteria of UL 9540A shall be marked with “This equipment meets the cell level performance criteria of UL 9540A for installation in Canada in accordance with the Canadian Electrical Code, Part 1.”
SEAC WG Modified Revision: e) Residential ESS on or in a dwelling unit shall be marked as follows: 1) If meeting the requirements of 23.2.2: “Suitable for Use in Residential Habitable Spaces”; 2) For systems intended for installation in Canada, systems meeting the cell level performance criteria of UL 9540A shall be marked with “This equipment meets the cell level performance criteria of UL 9540A”; 3) If meeting the requirements of 23.2.3 “Suitable for Use in Residential Non-Habitable Spaces”
SEAC WG Response: Accepting the comment in principle, but with changes in the proposal wording. Revisions will be proposed in a UL 9540 Recirculation Work Area in CSDS.

Section of UL 9540: 41.3f)7)
Comment Details: Comment #6 and #27
Proposal Language: None
Comment Suggested Revision: 6) Auxiliary output and input voltage (V), current (A) short-circuit current rating (kA) and frequency (Hz) if applicable; Add another line item number for Maximum input short circuit current rating.
SEAC WG Modified Revision: 7) Maximum Input short-circuit current rating (SCCR)  (kA);
SEAC WG Response: Accepting the comment. See also Comment Reference Number 6. Revisions will be proposed in a UL 9540 Recirculation Work Area in CSDS.

Section of UL 9540: 41.4B
Comment Details: Comment #28
Proposal Language: b) Short circuit current rating (SCCR) in Amps that each component can withstand from an external source; and
Comment Suggested Revision: b) Maximum input Sshort circuit current rating (SCCR) in Amps that each component can withstand from another part of the ESS if the connection point is a power input or bi-direction power connection an external source; and
SEAC WG Modified Revision: b) Maximum iInput short circuit current rating (SCCR) in Amps that each component can withstand from another parts of the ESS if the connection point is a power input or bi-direction power connection;   and
SEAC WG Response: Accepting the comment in principle, but with changes in the proposal wording. Revisions will be proposed in a UL 9540 Recirculation Work Area in CSDS.

Section of UL 9540: 41.4B
Comment Details: Comment #28
Proposal Language: c) Available fault current (as defined in Article 100 of NFPA 70) and time duration that the equipment can provide.
Comment Suggested Revision: c) Available fault current (as defined in Article 100 of NFPA 70) and time duration that the equipment ESS part can provide to another part of the ESS if the connection point is a power output or bi-directional power connection.
SEAC WG Modified Revision: c) Available fault current (as defined in Article 100 of NFPA 70) and time duration that the ESS part can provide to another parts of the ESS if the connection point is a power output or bi-directional power connection.
SEAC WG Response: Accepting the comment in principle, but with changes in the proposal wording. Revisions will be proposed in a UL 9540 Recirculation Work Area in CSDS.

Section of UL 9540: 42.5A
Comment Details: Comment #12
Proposal Language: None
Comment Suggested Revision: 42.5.1 When a UL 9540A report indicates evidence of external fire during the testing as allowed for ground mounted outdoor use only installations, the installation instructions shall indicate clearances from exposures that accounts for the length and location of the external flaming when establishing the exposure clearance limits with the following or equivalent wording: “The energy storage system shall be installed where the system is provided with clearance from exposures that are [10 feet plus the total length of flame measured] from the [location on the energy storage system where the flame exited]” In addition, the installation instructions shall warn about  special site considerations such as high winds or potential for exposure to dry vegetation that may require increased separation distances or special mitigation measures.
SEAC WG Response: Rejecting the comment. This is new content and needs to be reviewed and developed further. Please submit a Proposal Request in CSDS for future consideration by STP 9540.


This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Solar Energy and Technologies Office Award Number DE-EE0009002.0001. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.