Implementation Of Electrical Systems in Building

Core and shell buildings contain electrical systems that are far more complex in comparison to traditional methods of construction. In some cases, it can be difficult to implement electrical services, as they need to be designed to service tenants which are still unknown. Electrical engineering includes life safety systems such as fire alarm systems and power distribution, which are two key elements in building systems. This is becoming more important, especially in older buildings that do not have enough power to support the technology necessary in modern buildings.

Overall, electrical systems found in basic core and shell buildings can be very strategic in terms of controlling electricity throughout each floor. Existing in every building is an electrical transformer(s), a meter(s), and a panel or switchgear that distributes the power to the interior wiring that services the building. The location and sizes of these components vary considerably depending on the size and purpose of the building, the electric service provided, local code restrictions, and other factors.

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Typically, for reasons of efficiency, electric utilities will transmit electricity at high voltages which then allows the transformers to reduce this to lower voltages which can be utilized directly throughout the building. Most commonly found in wall and floor receptacles is 120/208 volts, and with some types of lighting fixtures or heavy machinery, up to 480/277 volts can be found. A commercial building of up to 25,000 sq ft (2500m2) will most often buy its electricity at these lower voltages. The utility company provides the transformer, which may be mounted overhead on a transmission pole, or on the ground, especially where transmission lines are wired underground.

A meter belonging to the utility company is installed on or in the building where the service wires enter, and the distribution within is by means of panels with circuit breakers that are located in an adjacent space known as an electrical closet. Each of these electrical closets houses one or more secondary transformers, which are smaller and used to step down from 480 volts to all the lower voltages needed for receptacles and machinery. In the case of a Class A Commercial building, one option would be to bring electricity to the building at 13,800 volts and then step it down to 480/277 volts using a large primary transformer or multiple transformers at the electrical service entrance. Primary transformers are known to be very heavy and require a deeper supporting structure in comparison to the rest of the building. They may be located either outside or inside the building depending where space is available, but an outdoor transformer mounted on a ground-level concrete pad is more of an advantage. This is because it is less expensive, cools better, easier to service, transmits less noise to the building, and is safer in terms of fire protection. These transformers do not need to be fenced except for reasons of visual concealment, in which there must be a clear space of 4 ft (1.2 m) all around the pad, for purposes of ventilation and servicing.

Another requirement is to have the concrete pad located within 30 ft (9 m) of a service road, as well as providing a service lane of 6 ft (1.83 m) wide between the transformer and the road. When dealing with larger buildings, multiple outdoor transformers can be used at intervals around the perimeter of the building to supply electricity as close as possible. Within a dense urban setting, it is mandatory that the primary transformer or transformers be located within the building. Utility companies will often provide oil-filled transformers for large buildings which must be placed in a transformer vault, known for being a fire-rated enclosure with two exits.

Another customary strategy is to have the transformer vault placed under the sidewalk, covered with metal grating to promote ventilation. Considering transformers and switchgear give off massive amounts of heat, they must be properly ventilated. The best location for them is against an outside wall so that high and low convective ventilation openings can be supplied. In the case where this isn’t possible, ventilation can also be achieved by access ductwork and fans connected to outdoor air louvers. It is mandatory to include access panels or doors for servicing/ replacing switchgear and transformers. Several large conductors run from these transformers to the switchgear and from the switchgear to the vertical and horizontal distribution components that feed electrical closets located throughout the building. Where it is important to maintain a continuous supply of electrical power, service can be brought to a building from two or more independent electric substations and routed through separate transformers and switchgear at the site, resulting in the building being less vulnerable to power outages caused by a single point of failure.

Throughout many large commercial buildings, on-site equipment capable of generating power during the event of disruption is also required. This equipment supplies emergency power for building systems essential to life safety, which includes alarm systems, fire detection, fire pumps, elevators, and emergency communications. It also provides standby power for less essential services. The electrical generators in this equipment are driven by engines fueled with natural gas, propane gas, diesel, or gasoline, with natural gas being the most beneficial in terms of its emissions. Power-generating equipment is best located on the ground outside the building, near the switchgear room, and fabricated weather resistant housings are available for this reason.