Revit Electrical Panels Explained
If you are utilizing Autodesk® Revit® for electrical engineering design, then you are using electrical panels and likely electrical panel schedules. While the process of inserting electrical panels and connecting basic circuits to them is pretty straightforward, there are some items that are good to know to help you better utilize panels and their associated schedules.
First off, a requirement in this process is to make sure that after you place an electrical panel in the Revit model, you set the Distribution System for it. Otherwise, you will not be able to connect any electrical device or other electrical equipment to the panel. The Distribution System is shown in both the panel’s Properties palette, and on the Options Bar on the ribbon.
Panel Schedules in Revit are a report of the information that is contained in the electrical panel, and schedules cannot be created without having a panel family placed in the project file. They are not like a spreadsheet where the numerical values are entered into the spreadsheet. The values shown in the panel and on the panel schedule are a result of connected loads to the panel and are only as good as the information in the items connected to the panel.
Following are some aspects of electrical panels and panel schedules that are important to know.
Circuit Numbering
When adding a circuit to a panel, Revit will assign the circuit to the first pole that is open on the specified panel per the Circuit Sequence setting value in the Electrical Settings dialog box.
The following options have been available since Revit 2015:
- Numerical (1,2,3,4,5,6,7,8,9,10,11,12)
- Group by Phase (1,3,5 / 2,4,6 / 7,9,11 / 8,10,12)
- Odd then Even (1,3,5,7,9,11 / 2,4,6,8,10,12)
You cannot specify a different circuit number when creating a circuit. I would love to be able to specify an actual circuit number when creating a circuit, especially for as-built projects. A common way to get the circuit to the desired pole is to move it on the panel schedule afterwards. Beginning with Revit 2015, there is a nice Move To button on the ribbon that allows you to pick the pole number where you want the circuit to be. Otherwise, you can use the Move Up/Down/Across buttons to relocate the circuit.
Another way is to place Spaces on the panel schedule in the slots preceding the desired location. This is not efficient for adding one circuit, but may be beneficial when you want circuits to start at a specific pole number. Just remember to go back and remove the temporary Spaces.
Replace Spare or Space with New Circuit Load
There are times when an electrical panel is not loaded with actual circuits, but has Spares and/or Spaces on the panel schedule to “fill” all of the poles of the panel schedule. It is possible to have a newly created circuit be assigned to this panel even if it is “full” (see Figure 1). If a Spare or Space is not locked, Revit will allow a new circuit to replace the first unlocked Spare or Space. When you specify this panel for a circuit, Revit will ask if you want to replace the Spare or Space with this circuit. You must answer yes.
Figure 1
Revit “locks” Spaces and Spares when you add them to a schedule, highlighting in a pale yellow/peach color, so this feature will not work by default. Therefore, you need to unlock Spares and Spaces to enable this to work.
Note that this only works if the specified maximum number of poles for the panel is equal to the “Max #1 Pole Breakers” parameter on the associated panel schedule.
Every panel has the instance-based “Max #1 Pole Breakers” parameter under the Electrical – Circuiting category. This parameter needs to match the “Number of slots shown” value in the Set Template Options dialog box when editing a panel schedule (see Figure 2).
Figure 2
If the panel occurrence has a quantity greater than the quantity of poles on the panel schedule, then the new circuit will be added to a circuit number that does not actually appear on the panel schedule. For example, if the panel says 84 “Max #1 Pole Breakers,” but the panel schedule shows only 42 poles, then a new circuit can be assigned to a circuit 43 to 64, but never be seen on the panel schedule.
If the specific panel instance has a quantity less than the quantity of poles on the panel schedule, then Spares, Spaces, and Circuits cannot be added to the panel schedule beyond the “Max #1 Pole Breakers” value.
Grouping Circuits
There are times when a device contains multiple circuits that need to be kept together in sequential circuit breakers. After assigning the circuits to the desired circuit numbers, highlight the desired circuits and select the Group/Ungroup command on the Circuits panel of the ribbon menu to keep them together.
An example of this is a floor box that has more than one circuit in the box, such as a furniture feed for multiple cubicles. You will typically want those circuits to be consecutive in the panel schedule. By grouping these circuits, they will always move together in the panel schedule.
Temporarily grouping circuits is also a great way to move a group of circuits at one time versus moving each circuit individually. Just remember to ungroup the circuits if they do not need to remain grouped together.
When circuits are grouped, the panel schedule will show a blue dotted line around the circuits that are grouped together. Each group has a separate rectangle encircling them.
Locking Circuits
It is often a good policy to lock your circuits on the panel schedule after you have them located as desired. This prevents circuits from moving unexpectedly. Circuits that are locked will not be moved on the panel schedule when you use the “Rebalance Loads” command on the ribbon.
This is not a requirement by any means and sometimes you want them to be unlocked to have more flexibility on the panel. If the location of individual circuits does not matter, then not locking them may be your best option. Spares and Spaces will be locked by default when you add them to a panel schedule. Locked circuits will be highlighted in a pale yellow/peach color.
Circuit Name
Each electrical circuit has a parameter named “Load Name,” which is the description that typically gets placed in the electrical panel as “Circuit Description,” “Description,” or something similar. This name can be changed either within the panel schedule or in the Properties dialog box for the actual electrical circuit. If the project file is using Revit Spaces (not to be confused with “Rooms”), then the Load Name parameter value will default to the Load Classification name plus the Space Name and Space Number. For example, if a receptacle with a Load Classification of “Receptacle” is placed in a space named “Office” and numbered 105, then the Load Name value will default to “Receptacle Office 105.”
Caution: The Update Names command on the ribbon will rename the Load Name parameter back to the default name for the circuit, which may not be what you desire.
Distribution System
I will not go into Distribution Systems much here other than to say that Panels must be connected into an electrical distribution system with other electrical panels, transformers, etc. for electrical loads to carry through the system (Figure 3).
Figure 3
Panel Load Information
Panel loads are a result of the electrical items connected to the panel. An electrical panel in Revit is generally classified as a Panelboard part type in the Electrical Equipment category. Panelboards are meant to pass loads through them and not to generate a load. A Panelboard cannot generate a load even if a connector on the Panelboard is assigned a load. Panelboards should be assigned the “Other” Load Classification.
Demand Load
Demand load is part of the panel information and not part of the circuit. Default panel loads <Val> that are shown on a distribution board show the Connected Load and not the Demand Load. Demand Load cannot be shown on a per circuit basis.
Demand Factor
Demand factors are applied at the panel level and not the individual circuit level. Revit will look at all of the families connected to the panel through circuits and find connectors in the families with similar Load Classifications. Those with similar load classifications are analyzed in whole at the bottom of the panel in the summary section. The demand factor is then applied to the entire specific load classification at once. The demand factor percent that is shown at the bottom of the panel is an average for all connectors that are assigned that demand factor. It will often show an unusual percent due to it being an average.
Motors
A motor demand factor will apply 125 percent load to the largest motor on the panel. It doesn’t matter if the motor is the last one added to the panel, as Revit will always find the largest motor. When multiple panels that contain motors are connected to a distribution board, the distribution board will only have one motor designated as the largest motor and will search across any of the connected branch panels to find it.
Receptacles
Typically, the first 10 kVA of the Receptacle load classification is calculated at 100 percent, and then the remaining Receptacle loads are calculated at 50 percent. Revit will calculate the load for all devices connected to the panel that use the Receptacle load classification and then apply the demand factor to display the proper demand load at the bottom of the panel in the summary area. If there is less than 10 kVA of Receptacle load on the panel, then all of the load will be at 100 percent. If there is 20 kVA of Receptacle load on the panel, then the second 10 kVA will be calculated at 50 percent so the Demand Load for Receptacles on the panel will be 15 kVA. When multiple panels are connected to a distribution board, Revit will only calculate the first 10 kVA of all receptacles on all those connected panels combined at 100 percent. The remaining receptacles are calculated at 50 percent.
If five panels each have 20 kVA of Receptacle load classification connectors, each of those panels will see a demand load of 15 kVA for receptacles. When those five panels are connected to a distribution board, the first 10 kVA of the 100 kVA total (five panels x 20 kVA) is calculated at 100 percent. The remaining 90 kVA is calculated at 50 percent for a load of 45 kVA. The panel will have a total demand load of 55 kVA for the distribution panel.
Spares
Adding Spares to represent loads on panels is a common occurrence for companies as a method to “cheat” Revit into showing what they desire on the panel. This creates items on the electrical panels that have not been truly circuited in the model. A “Spare” is added to the panel and then the description of the circuit is changed from “Spare” to the desired item. The desired load value is added to the leg (A, B, or C). This gives the appearance of the panel having correct loading on each leg as the leg totals at the bottom of the panel added up correctly. Sometimes, the entire panel schedule is made up of Spares with their descriptions renamed to fake a panel schedule. While this may look fine if you do not include the load totals, it is not truly Building Information Modeling (BIM) and is not accurate.
Power Factor Effect on Loads
When a power factor is assigned to a connector, it will show up on the Distribution panel.
- Val (default) on distribution board shows the full load without power factor applied. It uses the Connected Load parameter value.
- Apparent Current on distribution board shows the full load without power factor applied.
- True Current and True Load on distribution board shows the load with the power factor applied.
The load shows the full Connected Load (Apparent Load of the circuit) at the panel, including at the circuit level and at the totals at the bottom of the panel. A connector may have a 1 kVA apparent load assigned to it and a power factor of 0.1. At the branch power the circuit load will show as 1 kVA (1000 VA). At the distribution board, the load comes through differently depending on the parameter that is used on the distribution board. A differing value can signify that a family somewhere has a questionable power factor assigned to it.
- Val (default) on distribution board shows 1.0 kVA (1000 VA).
- Apparent Current parameter on distribution board shows 2.8 A.
- True Load parameter on distribution board shows 0.1 kVA (100 VA).
- True Current parameter on distribution board shows 0.28 A.
The value modified by the power factor is carried through to upstream panels/distribution boards/switchboards even though it does not show on the panel containing the originating circuit with the power factor.
Problem: Calculation between kVA and kW is kVA * PF = kW
- 1.0 kVA * .2 PF = .2 kW
- .2 kW is not the same as .2 kVA
While the True Load parameter for the circuit shows the correct number (.2 vs 1.0), the correct units is not set. The units can still say VA or kVA even though the units are actually W or kW. Revit needs to change the units to the appropriate value and not allow kVA to be shown if the internal power factor calculation has changed the value to kW. Branch panels do not have the ability to show the True Load parameter that will actually show the kW load with power factor applied. There is no parameter for Total True Load or Total True Current for showing total kW at the bottom of the panel schedule if desired.
Doug Bowers is a registered architect, LEED AP BD+C, and holds various Autodesk certifications. He provides education and implementation services for Revit, AutoCAD Architecture, AutoCAD, and Navisworks as an independent software consultant. He has been a repeat speaker at Autodesk University and enjoys making his classes both informative and enjoyable. Follow Doug’s clever tips, tricks, and workarounds at http://aectechtalk.wordpress.com.
