Exit Signs & Illumination in Transformer Vaults

Transformer vaults and switch gear rooms present unique hazards, such as high voltage and explosions, and as such, providing safe and adequate means of egress is a critical component to ensure timely evacuation during a fire or other emergency event. In addition to the prescriptive requirements of the Massachusetts State Building Code (780 CMR), the Massachusetts Electrical Code (527 CMR 12.00) also contains provisions to ensure workers and maintenance personnel are provided with quick exit access from these specialized rooms. The egress provisions from 527 CMR 12.00 to be considered for transformer vaults and switch gear rooms include the following:

  • An exit is required at both ends of the room where the switchgear and control panels exceed 6 feet in width unless:
    1. the location permits a continuous and unobstructed way of exit travel; or
    2. the depth of the working space is twice that required by NFPA 70 Table 110.34(A) (NFPA 70, 110.33(A)(1)).
  • The exit access doors are required to swing in the direction of egress and be equipped with listed panic hardware where the transformer vault / switch gear room contains equipment rated 800 A or more and the exit access doors are less than 25 feet from the nearest edge of the working space (NFPA 70, 110.26(C)(3)).

In addition to the requirements of 527 CMR 12.00, 780 CMR requires a transformer vault to be provided with traditional exit signage as well as floor proximity exit signage. The top of the floor proximity exit signs are required to be located 18” off the floor and adjacent to the opening side of the door. The last measure which is required for appropriate egress from these hazardous areas is the installation of egress illumination. The egress illumination can be achieved by providing emergency lighting in accordance with 780 CMR Section 1008 or luminous egress path markings in accordance with 780 CMR Sections 1025.2 through 1025.5.