Revit Electrical Systems - Crash Course
Nothing is as simple as one might like and using Autodesk® Revit® for electrical design is no exception. For those new to the software or to using it for electrical design, this article endeavors to jump start the journey by hitting the “must knows” and high points of using this highly complex software for electrical design. It will be assumed that the reader has a basic understanding of the Revit interface and electrical lighting and power systems.
The basis of electrical systems in Revit is defined in the Electrical Settings dialog. This is most easily accessed by typing the shortcut (ES). There is an icon in the Settings panel on the Manage tab of the ribbon or it can be accessed by clicking the cleverly hidden Southeast pointing arrow found in the bottom right-hand corner of the Electrical panel of the Systems tab (Figure 1).
The left-hand side of the Electrical Settings dialog lets the user navigate differing settings for Wiring, Voltage Definitions, Distribution Systems, and more. Simply select the area of interest on the left and its setting will appear on the right. The out-of-the-box settings in the Electrical-Default template should suffice for beginners to the software. That being said, users should verify that the required voltages are defined and the required distribution systems are present before proceeding (Figure 2).
Other settings worth a look include Hidden Line, General, Load Calculations, and Panel Schedules.
Panels and Equipment
With the basic electrical systems established, panels and other equipment should be added. In electrical terms, start from the service entrance and work your way out. Use the Electrical Equipment tool on the Electrical panel of the Systems tab or just type the shortcut (EE) to select an electrical panel (Figure 3).
In this example, the standard Lighting and Appliance Panelboard – 208V MLO 100A was picked. Once hosted on a wall, select the panel and supply a name for it in Properties. This panel has been named LP1A. Naming it in Properties supplies the name to the tag. The Tag by Category tool found on the Annotation tab is used to tag any category of Revit family, panels, receptacles, lights, and more (Figure 4). The shortcut key-in is TG.
Because Revit’s database has bidirectional associativity, editing the tag directly will also will push the name into Properties.
With the panel in place, there is now a means of powering lights and devices, as long as they run on the same distribution system as described in the Electrical Systems dialog above. Multiple distribution systems in the dialog provide multiple systems in the project (Figure 5).
The workflow Revit wants should start to become apparent when adding electrical devices.
- Select a category of family to add to the model on the ribbon.
- Use the Type selector to choose the exact type in the category.
- Place it as required on a vertical, horizontal, or work plane face.
- Adjust the instance properties of the family in the Properties palette.
- Tag if needed.
In this example, a duplex receptacle is chosen by picking the Electrical Fixture tool from the Electrical Device drop-down menu. It is hosted on an architectural wall and is automatically placed at 1’-6” above the level because the default family has been created at that height (Figure 6).
To connect the receptacle to the panel, first select the receptacle to be powered. Select the Power tool from the contextual Modify | Electrical Fixtures tab that appears (Figure 7). The contextual tab will change again, allowing the user to select an appropriate panel to circuit the receptacle. Select the LP1A panel created earlier. Revit displays a temporary homerun and arc at this point to indicate the connection to the panel. Just like temporary dimensions, they will disappear when the device is not selected.
If circuiting annotation is required, select the Wire tool from the Electrical panel on the Systems tab to place an arc and homerun arrow that can be adjusted in the view. Additional devices can be added to the circuit by selecting the first device and selecting the Edit Circuit tool and then selecting the desired devices to add. To remove a device, select Remove From Circuit on the Electrical Circuits tab and select the devices to be removed. Complete the operation by clicking the Finish Editing Circuit tool (Figure 8).
If two homerun arrows need to be combined, drag the end of one arrow onto a device (Connector icon) on the other device. Revit will combine these and place two arrows on the first circuit.
Lighting fixtures follow the same workflow as electrical devices and are powered the same way. They also have the ability to calculate an average estimated illumination level for spaces. Revit calculates the Average Estimated Illumination (AEI) for each space by dividing the Lumens contributed by each fixture at the lighting calculation work plane by the space's area. For those who need to know, the Lumens at the work plane (WL) = [Initial Intensity (II) x Light Loss Factor (LLF) x Coefficient of Utilization (CU)]. The
Room Cavity Ratio (RCR) = 2.5 x Room Cavity Height (RCH) x Room Perimeter (P) x Room Area (A).
Finally the Room Cavity Height (RCH) = Height of calculation plane (Lighting Calculation Luminaire Plane) – Height of the fixtures (Lighting Calculation Workplane).
This will only work if every light fixture family used has a light source for calculations and rendering. The light source will appear as a yellow blob in a 3D view. Be aware that many architectural light fixture families do not have a light source. When loading light fixture families, make sure to pull them from the MEP folder, not the Architectural folder.
Once a light fixture is placed in the model, access its type properties to associate the appropriate IES file downloaded from the manufacturer’s website. The IES file contains the information Revit needs to properly calculate light levels and render as designed. While in the fixtures type properties, adjust the Light Loss Factor and Initial Intensity as required (Figure 9).
Next, ensure a Revit Space is present in the room being evaluated. The Space tool is found in the Spaces & Zones panel of the Analyze tab. Edit the instance properties of the space to set the Limit Offset to envelope the light fixture, which is typically higher than 8’-0”. Verify the Lighting Calculation Workplane, and set the reflectances of the floor, walls, and ceiling (Figure 10).
Revit will automatically calculate the lighting levels. To see the calculated levels, create a Space schedule that includes the space’s name, number, and Average Estimated Illuminance as a minimum. By default, Revit prefers Lux to Footcandles. This can be changed in the Format tab of the Schedules properties dialog by selecting the AEI field and changing its Field format (Figure 11).
The resulting schedule will list AEI per space without much effort, helping guide the design in the early stages.
With equipment, devices, and lights in place, creating schedules helps leverage the database Revit creates to the needs of the designer. MA Lighting fixture schedule can be created the same way the space schedule was created. Panels schedules are a slightly different creature. Select a panel, then pick the Create Panel Schedule tool on the contextual tab. There is a standard template, but custom templates can be created to serve the needs of the individual firms. Once created, Panel schedules become available under their own heading in the Project Browser, similar to other schedules.
There is obviously way more available to electrical designs in Revit than can be covered in this article. The well is deep and that does not include user hacks and the growing pool of third-party add-ins. Hopefully, this “Crash Course” in the basics will help you kick off a long and productive journey.