ELECTRICITY

The first thing Montgomery Village resident Jeanette D’Amour does when she enters a building is look at the ceiling.

An electrical engineer, Ms. D’Amour can identify the type of lighting and the fire-suppression and air-handling equipment from the characteristics of the ceiling devices.

“That tells me what kind of building systems are in the building,” says Ms. D’Amour, electrical department head for E.K. Fox (EKF) & Associates Ltd., a consulting engineering firm in Fairfax City.

Electrical engineers like Ms. D’Amour design the circuitry and equipment that distribute power throughout a building, a task that, like the job of the production crew for a play, is behind the scenes and not something on most people’s minds.

“You’re not supposed to see it if we do our job right,” says Charles Sisung, senior electrical engineer for EKF and president of the Power Engineering Society, the Northern Virginia regional branch of the Institute of Electrical and Electronics Engineers (IEEE). IEEE is a technical professional association based in Piscataway, N.J., that sets international industry standards.

Electrical system design begins at the point where power supplied by an electrical utility company, such as Dominion Virginia Power or Potomac Electric Power Company (Pepco), enters a building. A transformer reduces the voltage carried from an underground cable or overhead lines to a level that is usable for the building.

Service conductors, usually copper wires, carry the power from the transformer to a switchboard or a switch gear, which are built to different standards, located in the main electrical room.

The switchboard or switch gear consists of a large panel with rows of switches and buses that distribute power throughout the building, along with fuses or circuit breakers able to protect the electrical circuit in case of current overload. The fuse link will melt or the circuit breaker will trip, opening the circuit to protect the loads.

A fuse or circuit breaker serves as a current sensor or current-monitoring device, says Charles Kim, assistant professor in the electrical and computer engineering department at Howard University in Northwest.

The current, or flow of electricity through a circuit, is measured in amperes. The amps are multiplied by voltage, or the pressure in the circuit, to determine watts, or power. Utility companies charge by the wattage used each hour, or kilowatt hours.

“Voltage is the power you’re getting. Amps is how much power the equipment draws,” says Russell Simpkins, electrical department head for Strickler Associates Ltd., a consulting engineering firm in Fairfax City.

Electrical equipment that is permanently wired is a fixed load, and plug-in equipment a convenience load, as described in Richard R. Janis and William K.Y. Tao’s textbook “Mechanical and Electrical Systems in Buildings,” Third Edition, published this year.

“Anything that consumes electricity, we call it load,” says Mr. Kim, who holds a doctorate in electrical engineering.

The equipment on each floor of a high-rise building receives power distributed from an electric room on the same floor or from panel boards located within the main electric room. The floor-level electric rooms are connected to the main electric room, typically located in the basement or lower level.

“A lot of times with a high-rise, instead of running wire to each floor, we use busduct, a copper material that can run in one piece from the main service to each floor,” Mr. Simpkins says.

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