Modeling Electrical Systems

Modeling Electrical Systems


In this lesson, you will learn how to model lighting and electrical elements in a project—lighting fixtures, electrical distribution panels, and switches—and connect them together by creating circuits, power systems, and switch systems. You will start by placing lighting fixtures in an architectural model, and then copy those elements into an Autodesk® Revit® MEP model. They will model the different lighting and power systems used to connect these lighting fixtures as well as create power systems and switch systems. The endpoint of the lesson will be an electrical model that can be used for analysis and shared with the other members of the design team and disciplines affected by the electrical design decisions.

Placing Lighting Fixtures in the Architectural Model

Designers often create lighting designs indicating the types of lighting fixtures and their layout as part of their preliminary design work. Similarly, you can place lighting fixtures in an architectural model to act as placeholders for items that will be specified in detail later by electrical designers on the project team. This two-stage approach enables you to consider the location of lighting fixtures in your early design decisions and indicate your design intent to other members of team.As you choose lighting fixture components to load into your project and use for your design, make sure that they are MEP-friendly (include electrical connectors, lighting values, and electrical load data in their definition). All of the lighting fixtures included in the libraries installed by the 2011 versions of Autodesk® Revit® software products are MEP-friendly, but older components may not be. To be certain, edit the component and look for the special electrical connector parts in its definition.


Figure 4.3.0 - Lighting fixtures in the linked architectural model are copied to MEP file

Copying Shared Elements into an Electrical Model

Link the architectural model to a Revit MEP host model and use the Copy/Monitor tool to copy the placeholder lighting fixtures to use as the starting point for our electrical design tasks. {slider Modeling Electrical Panels, Circuits, and Switches} Add electrical elements to the host project to model the key features and assign these elements to electrical power and switch systems. Place components to model the essential features of electrical circuits. The components available in Revit MEP include:

  • Electrical equipment
    • Transformers
    • Distribution panels
    • Switch gears
  • Devices
    • Electrical fixtures—receptacles and junction boxes
    • Communication—intercom system components
    • Data—Ethernet and other network connections
    • Fire alarm—smoke detectors, manual pull stations, and annunciators
    • Lighting—lighting switches, daylight sensors, occupancy sensors
    • Nurse call devices—call stations, code blue stations, and door lights
    • Security—door locks, motion sensors, and surveillance cameras
    • Telephone—telephone jacks
  • Lighting fixtures—ceiling, wall, and recessed lights

After placing electrical devices, you can:

  • Create power systems and switch systems.
  • Model circuits and wiring to link the devices together.
  • Assign circuits to panels.
  • Tabulate the loads on individual circuits.
  • View the devices assigned to each system in the System Browser.

Modeling Electrical Receptacle Circuits

Add components to the Revit MEP project to model the placement of electrical receptacles or outlets. Many receptacle types are available to meet different architectural needs, including:

  • Number of outlets available—simplex (single outlet), duplex (two outlets), quadruplex (four outlets)
  • Placement location—wall, floor, countertop, weatherproof
  • Voltage—110V, 220V
  • Special applications—switched, isolated ground, ground fault circuit interrupt (GFCI)

After placing receptacles, you can:

  • Create circuits and wiring to link the receptacles together.
  • Assign circuits to panels.
  • Tabulate the loads and view the devices assigned to each system in the System Browser.

Learning Objectives

After completing this lesson, you will be able to:

  • Understand how to place basic lighting fixtures in a building model using regular layouts.
  • Appreciate the process of copying model framework and lighting fixtures into a MEP file.
  • Understand how to create circuits and wiring to panelboard elements.
  • Model other common electrical equipment, such as switches and receptacles.
  • Explore the overall electrical systems that could be the basis for later system analysis.


Placing Lighting Fixtures in the Architectural Model

In this exercise, you will learn how to:

  • Choose and place lighting fixture components.
  • Array lighting fixtures to create regularly spaced patterns.

Figure 4.3.1 - Creating an array of lighting fixtures

Video Tutorial
Student Exercise
  • Place a regularly spaced array of eighteen 2' x 2' (0.61 m x 0.61 m) troffer lighting fixtures centered on the ceiling of the corridor on level 2 of the building.
  • Copy these corridor lighting fixtures and paste aligned to similar locations on levels 3 and 4.

Figure 4.3.2 - Troffer fixtures in the corridor arrayed in a regular-spaced pattern

Copying Shared Elements into an Electrical Model

In this exercise, you will learn how to:

  • Copy shared levels and grids into a Revit MEP host project.
  • Copy lighting fixtures from the architectural model into Revit MEP.
  • Create working views for lighting and electrical design.

Figure 4.3.3 - Copying lighting fixtures individually

Video Tutorial
Student Exercise
  • Copy the lighting fixtures from the architectural model into the Revit MEP electrical model using the Batch Copy option to copy all of the fixtures found.

Figure 4.3.4 -  Using batch copy to copy of the fixtures found in the linked model

Modeling Electrical Panels, Circuits, and Switches

In this exercise, students will learn how to:

  • Add electrical panels and specifying distribution systems.
  • Create circuits to connect lighting fixtures to panels.
  • Connect lighting fixtures to switches.
  • View electrical systems in the System Browser.

Figure 4.3.5 - Creating a switch system for many lighting fixtures

Video Tutorial
Student Exercise
  • Place a 208 volt MLO panelboard for the lighting fixtures on level 1 and designate its distribution system.
  • Create a power system circuit for the pendant lights in the retail space at the north end of level 1.
  • Add a single pole switch system for the troffer lights in the level 2 corridor.

Figure 4.3.6 -  Creating a power circuit between a series of lighting fixtures and an electrical panel

Modeling Electrical Receptacle Circuits

In this exercise, you will learn how to:

  • Load electrical receptacle components.
  • Place electrical receptacles on wall faces.
  • Create circuits to connect the receptacles to panels.


Figure 4.3.7. Creating a power system linking many receptacles

Video Tutorial
Student Exercise
  • Place electrical duplex receptacles in the conference room on level 3 of the building.
  • Create a power system for these receptacles and choose the arc wire option for the wires.

Figure 4.3.8. Power circuit linking receptacles to an electrical panel


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 witches 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" 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" above the floor and no higher than 54".

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 short 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.

Key Terms

Key Term
The system of individual electronic components, such as resistors, transistors, capacitors, inductors, and diodes, connected by conductive wires through which electric current can flow and service electrically powered devices.
The device where power can be monitored, distributed, and controlled safely via circuit breakers and ground connections.
Electrical power outlet serving the user’s plug loads.
Ground Fault Circuit Interrupt (GFCI)
GFCI is a safety feature that cuts power to a circuit when a ground fault or short is detected.