Transformers and Transformer Vaults (Including Secondary Ties)

NYC Admin. Code tit. 28, ch. 11, art. New York City Amendments to the 2020 National Electrical Code., art. 450

in effect

NYC Electrical Code § 450.14

Section 450.14 Section 450.14 – Revise Section 450.14 to read as follows: 450.14 Disconnecting Means. (A) Location. Transformers, other than Class 2 or Class 3 transformers, shall have a disconnecting means located either in sight of the transformer or in a remote location. Where located in a remote location, the disconnecting means shall be lockable open in accordance with 110.25, and its location shall be field marked on the transformer. (B) Rating. For all step-up transformer applications over 225 kVA, the selection of the Primary Disconnect and Step-Up Transformer shall be considered as an engineered system and shall be installed in accordance with 110.3(B) and in compliance with 110.9 and 110.10. The Primary Disconnect device shall be capable of handling the maximum inrush current of the specific transformer being installed. The selection shall be made by a registered design professional engaged primarily in the design, installation, or maintenance of electrical systems. The selection shall be documented and made available to those authorized to design, install, inspect, maintain, and operate the system.

NYC Electrical Code § 450.25

Section 450.25 Section 450.25 – Revise Section 450.25 to read as follows: 450.25 Askarel-Insulated Transformers. New installation of Askarel-insulated transformers shall not be permitted.

NYC Electrical Code § 450.42

Section 450.42 Section 450.42 – Revise Section 450.42 to read as follows: 450.42 Walls, Roofs, and Floors. The vault shall be of such dimension as to permit the installation of all electrical equipment in accordance with 110.26 or 110.34 as applicable. The vault shall be of fireproof construction with a minimum fire resistance rating of 3 hours with floors, walls, and ceilings 6 in. (152 mm) thick if made of concrete, or 8 in. (203 mm) thick if made of brick, or 8 in. (203 mm) thick if made of filled cement block. All building steel forming part of the vault construction shall have a comparable fire resistance rating. Each compartment within a vault shall be built to the same specifications in respect to the thickness of walls and fireproof door, as the vault. The floors shall have approved structural strength for the load imposed thereon to be installed in the vault. The floors and walls, to the height of the sill, shall be given a hard impervious finish and painted to prevent the absorption of oil. Exception: Where transformers are protected with automatic sprinkler, carbon dioxide, water spray, or approved gas suppression system, construction of 1-hour rating shall be permitted. Informational Note No. 1: For additional information, see ANSI/ASTM E119-18a, Method for Fire Tests of Building Construction and Materials. Informational Note No. 2: A typical 3-hour construction is 6 in. (150 mm) thick reinforced concrete.

NYC Electrical Code § 450.43

Section 450.43 Section 450.43(A) – Revise Section 450.43(A) to read as follows: (A) Type of Door. Each doorway leading into a vault from the building interior shall be provided with a tight-fitting door that has a minimum rating of 3 hours. Where practicable, basement vaults or vaults with an opening on a roof shall be provided with an outside entrance so that no entrance directly into the vault from the interior of the building will be necessary. Where entrance into the vault is from the interior of the building, the vault shall open into a vestibule, passage hall, or switchboard room not commonly in public use. Exception: Where transformers are protected with an automatic sprinkler, water spray, carbon dioxide, or approved gas suppression system, construction of 1-hour rating shall be permitted. Informational Note: For additional information, see NFPA 80-2016, Standard for Fire Doors and Other Opening Protectives.

NYC Electrical Code § 450.46

Section 450.46 Section 450.46 – Revise Section 450.46 to read as follows: 450.46 Drainage. Where practicable, vaults containing more than 100 kVA transformer capacity shall be provided with a drain or other means that will carry off any accumulation of oil or water in the vault unless local conditions make this impracticable. Such drain or other means shall be permitted to discharge only water accumulation and prevent discharge of transformer oil or coolant into a public or private sewer and shall comply with the New York City Construction Codes and other authorities having applicable regulations. The floor shall be pitched to the drain where provided.

Source: City of New York, Charter, Administrative Code and Rules (American Legal Publishing XML export, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/newyorkcity/latest/NYCadmin/0-0-0-232369Fetched: 10/24/2026