Power Distribution Equipment and portions of Power Distribution System shall be replaced when the assessment report establishes that the condition of the respective equipment is not acceptable, when there are known Code violations or capacity of existing equipment or service is not adequate to support new project equipment loads.
Major Power Distribution/service Replacement is usually addressed as a separate project and is based on assessment reports and preliminary O&M estimates.
Electrical Service Upgrade
Previous electric utility records shall be obtained to evaluate current consumption.
New service upgrade shall be provided if the existing service equipment is inadequate to serve the projected loads.
Existing 240V, 1-phase service(s) shall be considered to be removed and back fed by a new 208V service. Consideration must be given to 240V/1PH loads and if the change in voltage will alter the efficiency of the equipment. Buck/boost transformers may need to be added for loads that will not run properly on 208V.
New electrical service size shall include capacity for the following future loads based on existing conditions:
- Full building air conditioning or dehumidification system.
- Elevator(s).
- Kitchen loads.
- Computer loads.
A surge protection device (SPD) module shall be provided at the new service point.
Electrical Switchboard Upgrade
Live front service boards shall be replaced with new.
Service equipment that has surpassed its useful life (more than 50 year old on the average) and there are no spare parts for serviceability shall be considered for upgrade/replacement.
Service equipment that is rated at 240-volt, 3-wire systems shall be considered for replacement to be upgraded to a 4-wire system at 208-volt or 480-volt. Evaluate whether existing service(s) can remain in order to maintain serviceability to existing mechanical equipment and a separate service can be implemented. Coordinate feasibility of new services with the utility company. Coordinate work with mechanical equipment scope. If all existing mechanical equipment will be replaced with new, the existing 3-wire service shall be replaced with a new 4-wire service.
If the existing electrical room cannot accommodate the new service and respective switchboard, then the new service shall be located at a separate location and in a dedicated electrical room. Exact primary service location and primary feeder routing shall be coordinated and verified with the utility company. Confirm location of proposed pad mount transformer or pole mounted equipment with utility company and service accessibility to the facility. Service equipment shall be located adjacent to an exterior wall in order to minimize secondary feeder length. Coordinate routing of primary and secondary feeders with existing underground utilities or other potential site conflicts (storage oil tanks, etc.).
For instances where the electrical service size is adequate but existing switchboards do not have enough spare overcurrent protection devices or space for additional distribution; evaluate whether existing switchboards can be modified by extending bus and adding board sections. Consult with manufacturers or local vendors that can provide custom modifications to the existing board. If the latter is not feasible, evaluate providing a new switchboard at a separate location that can be fed either from the existing service feeders or through the implementation of a new service. New switchboard can back feed the existing switchboard or the existing switchboard can be removed and all existing loads can be connected to the new switchboard. Coordinate work with the utility company. Phasing plan of new service upgrades shall be included on design documents.
Ventilation of existing electric rooms with transformers shall be coordinated and designed by Mechanical.
Service switchover period shall be kept to a minimum and shall be coordinated with the school, the construction manager, and the utility company. Evaluate the need for a temporary generator to keep critical loads running during switchovers.
Electrical Distribution Equipment Upgrade
All live front distribution and branch circuit panels shall be replaced. Existing loads shall be reconnected to the new panel. In most cases, these are found in older buildings where the panel feeding existing electric unit heaters is original to the building. These panels are usually located in lower level mechanical spaces.
All existing non-emergency branch circuit panels with Type S screw fuses shall be replaced with new branch circuit breaker panels. Existing emergency fuse panels may remain if adequate capacity and branch circuit space is available in the panel.
Distribution panels with old ITE vacuum circuit breakers shall be replaced with new circuit breaker panels. Distribution equipment that has surpassed its useful life (more than 50 year old on the average) shall be considered for replacement or upgrade depending on condition and availability of spare parts for serviceability. Distribution equipment that is in deteriorated, rusted or other irreversibly damaged condition shall be replaced. Evaluate the cause of the damage and whether new equipment needs to be moved to a more suitable location.
Cloth insulated wiring (with or without asbestos): Confirm with the Managing Environmental Consultant (MEC) the status of any cloth insulated conductors. The MEC shall engage the services of a licensed electrician to assist in this evaluation. All actions in regards to the presence of cloth wiring shall be first evaluated and approved by the designated CPS representative.
- All feeders with cloth insulated wiring with asbestos (conduit and wiring) shall be replaced with new based on the MEC assessment, recommendations and applicable code requirements. Evaluate feasibility of providing new feeders to all respective loads.
- Feeders with cloth insulated conductors that do not contain asbestos shall be considered to be replaced with new. Consider the feasibility of reusing existing conduit.
All electrical distribution equipment shall meet code required clearance requirements. Evaluate existing mechanical piping located above electrical distribution equipment.
All electrical equipment spaces shall be free of any water leaks through the ceiling or seepage through the floor. Evaluate whether distribution equipment can remain at those locations or whether it needs to be relocated. Coordinate corrective actions that may affect other disciplines in order to address any problematic areas. Existing distribution equipment that may run “hot” or exhibit tripping of existing overcurrent protective devices per Building Engineer shall be evaluated.
New electrical distribution equipment shall not be located in corridors, janitor closets, rooms below swimming pools and other locations that do not meet good practice applications. Existing electrical panels located in janitor closets shall be evaluated. If they are in good condition and the project scope does not include the upgrade of the facility’s distribution equipment, those panels can remain in their current location.
Surge protection devices shall be provided at service switchboards and other distribution equipment as dictated by the CPS Design guidelines.
Mechanical equipment: Dedicated electrical distribution shall be provided to serve new mechanical loads. For major renovation or complete system replacements, refer to Volume 3, Chapter 9.2.2, Electrical Distribution.