Lighting And Electrical Systems Design Guide (Elementary School Building Example)

Distribution of electrical energy

The lighting and electrical design of elementary school is divided into following parts: electrical design, lighting design, fire alarm design, and telecom design. The school’s electrical system will consist of three-phase 480/277V power and three-phase 208/120V power. The incoming utility feed is assumed to be three-phase 4,160 Volt.

This incoming feed enters the building from the Park Avenue street side of the building running parallel with the natural gas, water, and telecommunications utilities.

The service terminates in the building’s main electrical room which is centrally located in the basement level. At the unit substation which consists of a main service breaker-disconnect, a 750 kVA delta-wye transformer, secondary breaker, and secondary switchgear distribution section, the main service is stepped down from a three-phase 4,160V delta to a 480/277V wye configuration.

Supplying standby power for the life safety and emergency branches will come from four Capstone 65kW natural gas microturbines, which will be discussed later in this document (Please see the attached electrical riser diagram for a more detailed organization of the electrical system).

The preliminary sizing for all equipment was based on a tabulation that can be found on page 25 of the supporting documents and also details of this equipment can be seen on pages 29-30.

Equipment Layout

As mentioned before, the unit substation will be located in the building’s main electrical room in the basement level.

Finally, each branch will be provided with a 480/277V lighting panel, transformer, and 208/120V double-tub receptacle panel in the main electrical room.