Modeling Electrical Systems

BIM for Architecture, Engineering, and Construction Curriculum


Placing Lighting Fixtures in the Architectural Model

How do recessed lighting fixtures affect the space available for other systems in the ceiling (for example, ducts and sprinklers)?

Recessed lighting fixtures require space for the fixture and clearances, thus reducing the space available for other ceiling systems, such as ductwork.

What are the advantages and disadvantages of using surface-mounted lighting fixtures versus recessed fixtures in the ceiling? Wall-mounted fixtures versus freestanding lamps?

Surface mounted lighting fixtures, by protruding into the space, are vulnerable to damage, but do not consume space in the ceiling. Recessed lighting fixtures are protected, but require space in the ceiling. Wall-mounted fixtures stay in fixed locations, but can create an obstacle, especially in hallways. Freestanding lamps offer great flexibility for placement as need, but are typically not used in public spaces, because they can be stolen.

What types of lighting fixtures are typically used to provide ambient lighting? Task lighting? Accent lighting?

Ambient lighting is often provided through ceiling troffers, ceiling mounted fixtures, and recessed downlights. Task lighting is typically achieved through under-cabinet strip lighting and local light sources - such as desk lamps - at the work location. Accent lighting can be provided through lamps, sconces, and cove lighting.

Copying Shared Elements into an Electrical Model

What are the advantages and disadvantages of using batch copy versus copying lighting fixtures individually?

The advantage of batch copy is speed and efficiency and is generally a better strategy, unless you want to only copy a few fixtures.

Why would you choose not to copy some lighting fixtures from the linked model?

If the fixtures are not necessary to our lighting and electrical design, then they should not be copied from the linked model. For example, freestanding lamps, being plug loads, need not be copied.

What factors determine whether it is better to copy the original types from the linked architectural model or map them to new types in the host MEP model?

In general it is better to copy the original types. The exception is if you have a lighting fixture that is not MEP-friendly (does not have electrical connectors and other MEP properties).

Modeling Electrical Panels, Circuits, and Switches

Where are electrical panels typically located? In public or private locations? Who should have access to the panels?

Electrical panels are typically located in central locations, such as corridors, stairwells, or electrical closets. They are typically locked or secured to prevent unauthorized tampering. Access is often restricted to building managers and maintenance personnel. 

How do you determine the number of distribution panels needed and the size for each?

The number of distribution panels needed depends on the total loads serviced and the rated capacity of the each panel. Each panel is sized to handle current and anticipated future loads.

Where are light switches typically located?

Light switches are typically loaded near doors, and access and egress points, so lights can be controlled as you enter or leave the room.

In what situations are three-way and four-way switches used?

Three-way and four-way switches are used when lights need to be controlled from several locations. Three-way switches control lights from two locations, while four-way switches control lights from three locations.

What are the advantages and disadvantages of using occupancy switches and timers versus standard switches?

Occupancy switches and timers are typically used to improve efficiency by turning off lights when they are not needed, for example when the room is unoccupied. The disadvantage is that timers and occupancy switches can turn off lights at the unintended times, for example, when the occupants are relatively still.

Modeling Electrical Receptacle Circuits

What is typical elevation for wall receptacles in different settings (for example, residential versus office)? What are the ADA requirements?

Wall receptacles have typically been placed at 12\" (0.30 m<\/em>) above the floor in residential settings. In office locations it is common to locate them at an elevation appropriate for the equipment serviced, for example, above desk-height in modular office systems. ADA requires that receptacles be mounted no less than 15\" (0.38 m<\/em>) above the floor and no higher than 54\" (1.37 m<\/em>).

Why are ground fault circuit interrupt (GFCI) receptacles used on countertops and in potentially wet locations?

GFCI receptacles provide an extra level of protection in potentially wet locations, by interrupting current when a ground fault (\u201cshort\u201d) is detected. This is especially important in bathrooms, on countertops near sinks, and anywhere water is used. 

When should quadruplex (four-outlet) receptacles be provided?

Quadruplex receptacles should be provided when a large amount of electrical equipment is likely to be used or placed there, for example, near home entertainment centers or where computer equipment will be used. This minimizes the need for power strips which can create safety hazards.