Electrical System
Home Wiring Calculations


Macalister Hall was designed in 1969 and construction was completed construction in 1974.  Electricity is the most widespread form of energy in a modern building.  It distributes not only electric outlets and electric lighting, but also the motive power for ventilation, heating and cooling equipment, traction power for elevators and material transport, plus power for all signal and communications equipment.  That’s the reasoning behind the helplessness of a facility during an electric power failure.  Although, if accurately calculated, the facility returns to partial functioning by virtue of emergency equipment that provides some part of the facility’s electricity demands for a limited amount of time.  Given this complete dependence on electric power for normal functioning, it is apparent that planners must be familiar with normal electric systems.  Historically, burning a fossil fuel, such as coal or oil, most often produced usable energy.  The resultant heat energy was used directly as heat and light or converted by machines into motion.  However, only since the end of the 19th century has this heat been used to create another form of usable energy, electricity.  Even the recent partial substitution of nuclear for fossil fuels has affected only the heat production portion of this process.  Beyond that point, the heat is utilized in the same manner to drive generators that produce electricity.  Therefore, it is well to remember that in terms of natural resources, electricity is an expensive form of energy because the efficiency of he overall heat to electricity conversion, on a commercial scale, rarely exceeds 40 percent.

Electrical Systems:

Electricity represents a type of energy itself that occurs naturally only in unfeasible forms such as lightning and other static discharges or in natural galvanic cells that cause corrosion.  The primary problem in the utilization of electric energy is that unlike fuels or even heat, it cannot be stored and therefore must be generated and utilized in the same instance.  This requires an entirely different model of utilization than, for example a heating system with a fuel source, burner, piping and associated equipment.  The bulk of electric energy used today is in the form of alternating current (ac), produced by ac generators, commonly called generators.  Direct current (dc) generators are utilized for special applications requiring large quantities of dc.  In the building field or in the case of MacAlister, such a requirement was once universal for elevator work because of the ease with which with dc motors can be speed controlled.  However, today designers would have used technology to install ac motors that are controlled by fine speed control ac motors in MacAlister.  Moreover, these motors save energy and reduce machinery space requirements.  MacAlister also was designed to utilize dc for smaller quantities that are furnished by batteries, photovoltaic equipment or by rectifiers for telephone, signal equipment, controls and other specialized uses.   

Electrical Equipment Overview:

The following equipment is located in Macalister Hall, and typical of other buildings, will be discussed in this building analysis.  The major components MacAlister’s and most building’s electrical system can be arranged in three major categories; wiring and raceways, power-handling equipment and utilization equipment.  In the first category, we include conductors and raceways of all types; in the second, transformers, switchboards, panel boards, large switches and circuit breakers; and in the last category utilization equipment such as lighting, motors, controls and wiring devices. 

Typical Single Line Diagram of a building electrical distribution system

The above diagram is also called a building block diagram, because the major components are shown as rectangles, or blocks.  The diagram illustrates the incoming service, for which MacAlister probably utilizes 13,200 volts judging by the building square footage and program uses.  It also illustrates the utilization items at the end of the system.  The connecting conductors between major system components are drawn to reflect size and thereby power handling capacity.   

    This figure represents a diagrammatic, pictorial representation of a typical building electrical power system with the power capacity being indicated by the size of the conductors.  The diagram does not extend beyond the local panel board and includes commonly used items. 

Electrical Room Space Allocation:

There are two major electrical rooms located in Macalister Hall, one in the basement and one on the roof. A classification of the spaces follows.

Basement Electrical Room

The basement electrical room houses the transformer room, main switchboard, main feeders and some distribution panels for the basement mechanical components.  There is also an electric room that distributes power to Mandell.  The electrical room measures approximately 500 square feet and is shown in the green hatch below.



Penthouse Electrical Room

The penthouse electrical room is primarily the elevator shaft space, but there are panels that directly fed from the basement to power the predominantly mechanical penthouse. The elevator machine room is shown in green below:  



Construction Materials:

            The selection of electric materials involves not only choosing a material or assembly that functionally adequate and, where necessary, visually or satisfactory, but also the consideration of economic factors.