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Energy storage system installations – Code File, October 2021

October 22, 2021 | By Nansy Hanna, P.Eng.

“As with every new technology, there is a need to balance innovation against safety.”

October 22, 2021 – Energy storage can facilitate the integration and adoption of renewable energies, distributed generation and electric vehicles, and can also be used as backup power—keeping the lights on when the power goes out.

The falling costs of storage—as well as the falling costs of renewables, especially solar—are introducing opportunities for greater storage adoption. This, plus the drive toward net zero, has contributed to the need for energy storage systems (ESSs).

To assure ESS project success, it is imperative that installations are done in a safe manner. To that end, ESSs were added to Section 64 of the CE Code (2021 ed.). The new Subsection 64-900 aims to provide clear installation requirements for these systems, and to harmonize with other codes and standards.

Although they are not a renewable energy, ESSs introduce the same challenges when discharging energy to an interconnected supply authority system. The loading on the electrical system when charging is also addressed in the new Subsection.


Some important additions include:

• Definitions of the different types of ESSs.
• Marking requirements for buildings with ESSs.
• Requirements for disconnecting means.
• Restrictions on where ESSs may be located, and required separations from structures and/or equipment.

In addition to the Rules in 64-900, the general Rules in Section 64 apply to energy storage systems. Additionally, Section 84 requirements concerning any power production sources intended to be interconnected with the utility are applicable, including the need to comply with utility requirements.

Rule 64-002 definitions clarify that all types of ESSs are required to conform to the joint Canada-U.S. standard ANSI/CAN/UL 9540 “Energy storage systems and equipment” (except for those that are field-assembled and have a storage capacity of less than 1 kWh).

Rule 64-918 allows ESSs to be installed in garages of dwellings, directly mounted to the building surface, installed in or on a detached garage, storage building, or free-standing structure, for up to 20 kWh for single ESSs and 40 kWh (aggregate) for multiple systems (when spaced 1 metre apart). The limitation on the capacity is waived when the ESS meets the cell level test from ANSI/CAN/UL9540A “Standard for test method for evaluating thermal runaway fire propagation in battery energy storage systems”. Additionally, Rule 64-918 does not permit systems greater than 1 kWh storage capacity to be installed in dwellings or living spaces of residential occupancies.

This limitation has sparked some debate, as well as a desire to compare against other North American standards. Let’s explore the relevant sections in some of these standards:

ANSI/CAN/UL9540 is used to approve ESSs

• Clause 23.2.2 requires that ESSs intended for use in the living space of dwelling units meet the performance/cell level test requirements in ANSI/CAN/UL 9540A. It then requires systems complying with these requirements to be marked “Suitable for residential use where permitted”. This marking could cause confusion, as it suggests that only ESSs marked “for residential use” are permitted in dwelling units. However, Clause 23.2.2 clearly states ESSs intended for use in the living space of dwelling units are required to meet the test and be marked.

• Table E.1 “Residential use ESS” further clarifies this issue by showing the capacity of ESSs permitted indoor within utility closets, attached garages or utility and storage spaces. Note B in the Table reaffirms that ESSs tested in accordance with the 9540A cell test method can be installed in living spaces of dwelling units.

• However, no energy storage system has been certified to meet the UL9540A cell level test, as yet.

NFPA 855 “Standard for the installation of energy storage systems”

• This standard does not permit ESSs to be installed in living areas of dwelling units or in sleeping units; however, it does permit ESSs within utility closets and storage or utility spaces.

The International Residential Code (IRC 2021), Section R328

• This standard permits ESSs in enclosed utility closets, basements, and storage or utility spaces within dwelling units with finished or non-combustible walls and ceilings.

As energy storage systems continue to evolve so, too, will the CE Code. As with every new technology, there is a need to balance innovation against safety.

On the one hand, safety considerations should not be so restrictive that they stifle innovation. On the other hand, when there are not enough safety measures in place, the increased risk to people and property can disrupt of the adoption of new technologies.

This is why the CE Code is updated every few years, as it provides regulators and industry the opportunity to recalibrate and maintain this balance.

Nansy Hanna, P.Eng., is senior director, Engineering & Regulations, at Ontario’s Electrical Safety Authority (ESA). She is also chair of the Canadian Advisory Council on Electrical Safety (CACES) and a member of the ULC Advisory Council, CSA Technical Committee on Industrial, Consumer and Commercial Products and CSA CE Code-Part I, Sections 24, 32, and 46. She can be reached at nansy.hanna@electricalsafety.on.ca.

This column—plus more great content—appears in the October 2021 edition of Electrical Business Magazine. Even more back issues are located in our Digital Archive.

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