Yosemite Valley District/Museum Building Electrical Rehabilitation
The Valley District/Museum Building is a historic multiple story building that houses a public museum, exhibit room, research library, meeting rooms, and 12 multi-divisional office spaces. The approximate floor space area is 20,000 square feet. The existing electrical service components are of various ages dating back as far as the 1930s and the condition of these components significantly increases electrical fire potential and is an extreme hazard to visitors, maintenance personnel, and other staff. Current electrical code violations include NEC 110.12 (workmanship), NEC 110.26 (clear space), NEC 210.11 (branch circuit quantity), NEC 250 (grounding), NEC 406.3(A) (receptacle grounding).
This project, all work to be performed by a licensed contractor, will rehabilitate the electrical system and bring it into current electrical code compliance by completing the following:
1. Removing and replacing the existing 300 amp breaker with a 400 amp breaker, using the existing main switchboard, including installation of a new utility meter and current transformers. The existing main switchboard is not located in the District/Museum building, but across Village Drive in a utility maintenance yard. Connections to the main switchboard will utilize existing conduit and conductors, therefore there is no ground disturbance associated with this project.
2. Removing and replacing seven electrical service panel boards. Panels will be replaced in the current locations, to minimize any disruption to the historic fabric. Where limited patching is necessary, it will use a 3-coat system plaster finish, patched and painted to match. The plaster mix has been specified by the consultant's Historic Architect to match the existing finish.
3. Installation of two new electrical service panel boards. One new panel board will be installed in a storage area on the first floor, and the second panel board will be located in a storage area in the attic. Both of these areas are considered non-contributing to the historic character of the building, per the 2007 Historic Structure Report. New feeder lines in new conduit will be installed to connect the new panels. Conduit will be surface run, and painted to match existing, and will be located in the storage area on the first floor and the attic storage area.
4. Removing and replacing feeder conductors to the existing electrical service panel boards. To avoid disturbance to, and penetrations of, the historic finish, existing conduits and raceways are being utilized to run the new conductor lines. New penetrations will be limited to the areas directly adjacent to the two new electrical service panels, to surface the conduit into the service panel.
5. Removing and replacing all electrical service devices, such as receptacles, switches, dimmers, and wire-mold components. All replacement devices will be provided with new grounding bushings and pigtails in the existing back-boxes. Any wire-mold that is no longer needed will be removed, and the existing surface repaired and painted to match.
6. Temporarily removing each lighting fixture, properly grounding the fixture, and then reinstalling the fixture. Connecting all existing lighting circuits to ground fault circuit interrupter (GFCI) breakers in the associated panel. Three historic lighting fixtures will be refurbished to original condition and then reinstalled.
7. Installing GFCI receptacles or GFCI circuit breakers, in instances where testing indicates that proper grounding cannot be achieved by replacement of grounding bushing and pigtails.
8. In the Research Library on the second floor, additional duplex outlets are being installed using surface mounted wire-mold and table mounted tele-power poles. Connection will be made at existing junction boxes, reducing penetrations of the historic finish.