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O 1997 Portland General Electric. All rights reserved. Ventilation Ventilation is required in a building vault to dissipate the heat generated in the transformers. The customer is responsible for designing and providing the ventilation, which must meet all national and local codes, (NEC 450-45, etc.). Requirements are the same for a transformer room as for a three-hour vault. It can be by natural convection or forced air. Natural convection is preferred since a fan is not required. A limitation on vent sizes may require forced-air ventilation. See Vaults - 200 Amp ~- System Maximum Design Standard, STD. LD-310-00, "Vault Ventilation° section for ventilation criteria. Size Room size should be sufficient to allow movement around the transformer and allow proper radii on primary and secondary raceways. In general, the vault shall be no smaller than the dimensions necessary to allow 3 cubic feet per kVA of maximum transformer capacity. Doors Door openings should be large enough for a transformer to be installed or removed through a doorway. Because of the confined space, design for the largest width of transformer. Double doors will often be required and the doors shall open out. Doors shall be equipped with focks, and accessible to PGE personal. The doors shall be kept locked, access being allowed only to qualifed persons. Vault Locations and Access Location The vault location is usually a compromise between the customer and PGE. It is advantageous for the vault to be adjacent to the main electrical room. It is preferred to have the vault at or below ground level. A roof vault is acceptable if the customer can provide an elevator or crane with capacity for the initial transformer installation and any future replacement. The vault should be as close to the primary location specified by PGE as possible to avoid long conduit runs with several bends. Access It shall be possible to enter the vault 24 hours a day. Access into the vault itself is controlled by PGE. Doors into a vault shall open out for safety considerations and shall be of sufficient width to remove the widest piece of equipment. Hatches or lift-out slabs may be used for equipment access, allowing a smaller door to be used for personnel access. Access ways, hallways, elevators, etc. shall also be of sufficient size to move equipment into and out of the vault. Large transformers (250 kVA and up) are usually installed through a hatch door or lift-out slab. Dimensions of the hatch shall allow one to two feet of clearance around transformers when lowered. PGE PROPRIETARY MATERIAL - THIS INFO IS BASED ON ASSUMPTIONS 8 CRITERIA `NNICH MAY NOT BE VALID OUTSIDE T}iE PGE ELECTRIC SYSTEM - FOR INTERNAL USE ONLY UNDERGROUND BUILDING CLASS A VAU LTS UNDERGROUND P.G.E. CO. STANDARD X I DESIGN I I CONSTRUCTION I T&D STANDARDS I DATE 08-09-96 LD-310-07-08 ~~ ~Ba~'E~ : Menu - C-vse -