The Ontario Building Code | Electrical Equipment Vaults
3.6.2.7. Electrical Equipment Vaults
(1) Where an electrical equipment vault is required by the Electrical Safety Code adopted under Ontario Regulation 164/99 (Electrical Safety Code) made under the Electricity Act, 1998, the electrical equipment vault shall be totally enclosed by a fire separation of solid masonry or concrete construction having a fire-resistance rating of not less than 3 h if the vault is not provided with an automatic fire extinguishing system and not less than 2 h if the vault is so protected.
(2) Where a building is required to be sprinklered, the electrical equipment vault described in Sentence (1) need not be sprinklered provided,
(a) the vault is designed for no purpose other than to contain the electrical equipment, and
(b) a smoke detector is provided in the vault that will actuate the building fire alarm system in the event of a fire in the vault.
(3) A vault, that is part of a building and houses electrical equipment indoors, shall have,
(a) roofs or ceilings consisting of reinforced concrete of adequate strength for the conditions and not less than 150 mm thick, and
(b) floors consisting of reinforced concrete of adequate strength for the conditions and not less than 150 mm thick, except that floors that are at excavation level are permitted to be of reinforced concrete not less than 100 mm thick.
(4) Walls, roofs or ceilings, and floors shall be adequately anchored together in a manner designed to resist dislodgement by explosion.
(5) Only pipes or ducts necessary for fire protection or the proper operation of the electrical installation shall penetrate the fire separations surrounding the electrical equipment vault.
(6) A ventilation duct or opening, that penetrates the fire separation to the outdoors, need not be protected by a closure at the penetration.
(7) Each door to an electrical equipment vault shall be provided with a substantial lock or padlock.
(8) Explosion-relief devices and vents or other protective measures shall be provided for every electrical equipment vault containing dielectric liquid filled electrical equipment in conformance with Sentence 3.3.1.19.(2).
(9) Every electrical equipment vault shall be provided with a ventilation system designed in conformance with Part 6 to prevent the ambient temperature in the vault from exceeding 40°C.
(10) Where the vault ventilation system in Sentence (9) is directly from an outdoor area by natural ventilation without the use of ducts, and where the electrical equipment is the principal source of heat, the combined net area of inlet and outlet openings shall be not less than 0.002 m2/kVa of electrical equipment capacity with a minimum of 0.093 m2, except that,
(a) where equipment in the power class as described in CAN/CSA-C88-M, "Power Transformers and Reactors" is installed, ventilation requirements are permitted to be based on the actual full-load losses, or
(b) where the equipment is installed for emergency purposes only and is not normally energized, it need not be considered in determining the ventilation requirements.
(11) In the vault ventilation system in Sentence (10), the inlet for fresh air shall lead from an outdoor area and shall terminate at a point not more than 1 000 mm above the floor level of the vault.
(12) Where the vault ventilation system in Sentence (9) is a mechanical system, it shall be separate from the system for the remainder of the building and shall be designed so that,
(a) the vault temperature is thermostatically controlled,
(b) the fan is located so that it may be serviced without danger to personnel,
(c) a high temperature alarm is provided in the vault,
(d) the system is automatically shut off in the event of a fire in the vault, and
(e) a filter is provided in the air inlet if there is a possibility of dirt being drawn in.
(13) All ventilation openings shall be protected in conformance with Sentences 6.2.3.12.(3) and (4) and the protection shall be installed in such a manner that it cannot be removed from the outside by the use of common tools and it is tamperproof.
(14) Except as permitted in Sentence (15), the floor of the electrical equipment vault described in Sentences (1) and (2) shall be liquid tight and surrounded by liquid tight walls and sills of sufficient height to confine within the vault all of the liquid from the largest item of electrical equipment, but to a height of not less than 100 mm.
(15) The floor of the electrical equipment vault described in Sentences (1) and (2) may be provided with a floor drain connected to a covered sump capable of holding all of the liquid from the largest item of electrical equipment, and the connection shall have a noncombustibletrap to prevent the spread of fire from the vault to the sump.
(16) Where the electrical equipment vault is located in a hazardous location classified as Class II, Division 1 in accordance with the Electrical Safety Code adopted under Ontario Regulation 164/99 (Electrical Safety Code) made under the Electricity Act, 1998, it shall have,
(a) no vent opening except to the exterior of the building, and
(b) suitable pressure-relief openings communicating only with the air outside the building.
(17) Where doors are provided between the vault described in Sentence (16) and the rest of the building, they shall have suitable seals such as weatherstripping to minimize the entrance of dust into the vault.
(18) Every electrical equipment vault shall be provided with,
(a) adequate lighting, controlled by one or more switches located near the entrance,
(b) luminaires located so that they may be relamped without danger to personnel, and
(c) a grounded receptacle located in a convenient location inside the vault, near the entrance.