In the Wiring settings section of the dialog box, you can define the ambient temperature to be used in order to apply a correction factor to the load of a circuit. The default setting is 86°F (30°C), which applies a correction factor of 1 for any of the three wire temperature ratings. In this section, you can also define the size of the gap that Revit MEP 2011 displays when wires cross. The value you input into this setting is for the print size of the gap on a full-size print.

Tick marks for wiring are also defined in the Wiring section of the Electrical Settings dialog box. You can create an annotation family to use as a tick mark if the defaults do not comply with your standards. The family must be loaded into your project in order for it to be assigned to represent hot, neutral, or ground wires. You can choose to show a slanted line across the tick marks to represent the ground conductor no matter what families you use. There are three options for when your tick marks will be displayed, as shown in Figure 14.1. Changing the display setting for tick marks will affect all wires in your project.

New to Revit MEP 2011 are the settings for defining the maximum voltage drop for branch circuits and feeders.

The Wire Sizes section of the Electrical Settings dialog box allows you to define the sizes of wires you want to use for different circuit ampacities. You can set the wire sizes for aluminum and copper wire. You can even create a different wire material if your project requires it. You can vary the wire sizes for the three standard wire temperature ratings and for different types of insulation. This gives you the ability to control what types of wires are used for different circuits because you can remove ampacity ratings for different wire temperature and insulation combinations.

Figure 14.1. Wiring section of Electrical Settings dialog box

The Used By Sizing column allows you to establish which wire sizes are available for Revit MEP 2011 to use when wire sizes are calculated. You can assign only one wire size per ampacity, so if, for example, you want to use #12 wire for 15 amp and 20 amp circuits, you would have to delete the 15 A ampacity and set the size for the 20 A ampacity to #12. This does not mean you cannot use a 15 A circuit in your project. Revit MEP will use the smallest wire size available in your list for an ampacity smaller than the smallest in your list. Figure 14.2 shows an example of wire sizes for a project. Any 15 amp circuits in the project will have to use #12 wire.

Figure 14.2. Wire size settings

The Correction Factor section of the Electrical Settings dialog box is for setting a correction factor based on temperature to be used in load calculations. You can set correction factors for the three wire temperature ratings for both aluminum and copper wire. The Ground Conductors section allows you to set the equipment grounding conductor size for different ampacities of different wire materials. So, for wire sizing, you have the ability to control several factors that determine the wire sizes that are calculated for your circuits.

The Wiring Types section of the Electrical Settings dialog box is where you can create different types of wires for different uses. By creating different wire types, you have the ability to assign all the desired settings to a type, and like component families, you can switch between wire types in the model. Creating wire types also provides you with an easy way to control the visibility of certain wires by using a view filter. You can give your wire types unique names that define their use or some characteristic about them. You can set the material, temperature rating, and insulation used by a wire type. You can also set the maximum wire size for a type. If a circuit requires a larger wire size than the maximum, Revit MEP 2011 will automatically create parallel sets of wires that do not exceed the maximum size to accommodate the load. You can establish whether your wire type requires a neutral conductor and, if so, set the neutral size to equal the hot conductor size or set it as an unbalanced circuit. After the neutral conductor is sized, the value you input for the neutral multiplier is assigned. Although Revit MEP 2011 has conduit tools for modeling, you can set the conduit material for your wire type, to be used for voltage drop calculations. Figure 14.3 shows some examples of wire types created for a project.

Figure 14.3. Wire types

In the Electrical Settings dialog box, the Voltage Definitions section is for establishing the minimum and maximum values for the voltages used in your project. This allows for different ratings on devices or equipment. These voltages will be used to establish different distribution system definitions. You can add voltages to your project by clicking the Add button at the bottom of the dialog box and giving it a name and minimum and maximum values. To remove a voltage from your project, select the voltage, and click the Delete button at the bottom of the dialog box. You will not be able to delete a voltage if it is used by a distribution system definition in your project. You must delete the distribution system first, and then the voltage can be deleted. Setting up standard voltage definitions in your project template will save you time when setting up a project. Figure 14.4 shows some standard voltage definitions.

Figure 14.4. Voltage definitions for a project

You can define the distribution systems to be used in your project in the Distribution Systems section of the Electrical Settings dialog box. The connectors in your electrical families need to coincide with the systems you define so that you can assign devices and equipment objects to a system. You can create single or three-phase systems in delta or wye configurations and establish the number of wires for the system. The line-to-line and line-to-ground voltages for a system can also be defined. It is important to note that Revit will let you create systems that do not actually exist in the industry. For example, you could create a three-phase system and set the line-to-line voltage to 120 volts and the line-to-ground voltage to 277 volts. Use caution when creating distribution systems because they are very important for creating circuits for devices and equipment. Voltages can be assigned only to line-to-line or line-to-ground if they have been defined in the Voltage Definitions section. Figure 14.5 shows some examples of distribution systems created for a project.

In the Load Calculations section, you can establish demand factors and load classifications. The load classifications of the connectors in your electrical families determine which demand factor they will take on in your project. In this section, you can deselect the check box so that calculations for loads in spaces will not be done, which can improve the performance of your project.

When you click the Load Classifications button in this section, the Load Classifications dialog box opens. In this dialog box, you can create new load classifications and define the demand factor used for them and a lighting or power load class for use with spaces. The available demand factors appear in the drop-down list, and the Demand Factors dialog box can be accessed by clicking the button next to the Demand Factor drop-down, as shown in Figure 14.6.

Figure 14.5. Distribution systems for a project

It is best to keep your load classification names simple and descriptive because you will have to assign them to the connectors in your electrical families. When working in the Family Editor, you can use the Transfer Project Standards tool on the Manage tab to transfer load classification settings from your project or template file into the family to ensure coordination.

There are many load classifications that come with the default electrical templates. You can create your own using the buttons below the list, in the lower-left corner of the dialog box. The Spare classification cannot be assigned a demand factor and cannot be transferred to family files for use on connectors. It exists so that spares can be accounted for in your panel schedules.

In the Demand Factors dialog box, you can define the demand factors that are assigned to load classifications. The default electrical templates come with an extensive list of demand factors, and you can create your own using the buttons in the lower-left corner of the dialog box. Figure 14.7 shows the Demand Factors dialog box. The Calculation Method section is where you determine how the demand will be calculated. Additional load can be added to the calculated result using the check box at the bottom of the dialog box.

There are three methods that can be used for calculation:

Figure 14.10. Incremental demand factor settings using the By Load method

The electrical settings established for your projects are the backbone of creating circuits and wiring. Properly set up in your project template, they can make creating and managing circuits easy and efficient.

Real World Scenario: Settings for Templates

Duncan and Abbey Engineering has recently broadened its range of project types. Making the transition to Revit MEP 2011 has opened up opportunities to pursue projects that the company normally would not do. It recognized the power of having a Revit template for its projects and quickly set up templates with electrical settings for the different project types. Duncan and Abbey Engineering is now doing work in different countries that require unique settings for voltage and distribution systems. Having templates with preset electrical settings for each of its clients unique standards saves the company time and reduces the possibility for error.

If the wiring that is automatically generated is not exactly how you want to show the connection of the devices, you can edit it after it is created. When you select a wire, there are grips that allow you to change the arc and location of the wire.

Figure 14.14. (a) Indicated home run for a circuit; (b) wire automatically generated by clicking Arc button on Convert To Wire panel

Figure 14.15. Multiple items selected for a circuit

Figure 14.16. Select Connector dialog box

The small blue circles that appear near the ends of the wire are grips for changing the endpoints of the line that represents the wire. These Change End Offset grips do not represent the point where the wire is connected, only the graphical representation of the wire. The actual point of connection is indicated by the connector symbol

The larger blue circle with two lines tangent to the endpoints of the wire is for changing the arc of the wire. The + and – grips that appear near the wire are for adding or removing hot conductors. These are discussed later in this chapter. Figure 14.17 shows the editing grips for a wire.

Figure 14.17. Wire editing grips

The wire shown in Figure 14.18a can be edited with the grips so that it is drawn from the symbols correctly and does not interfere with other devices that are not part of the circuit, as shown in Figure 14.18b. The end offsets are changed, and the arc of the wire is reversed for a cleaner-looking drawing.

Figure 14.18. (a) Wire that needs to be edited; (b) the results of using the grips to change the appearance of the wire

You can use the connection point grip to change what object a wire is connected to. Click and drag the grip to a new object to connect the wire to it. If you click the connector grip and drag it off an object, a home run wire will be created. When changing the connection point of a wire, it is a good practice to make sure you snap to the connection point of the object you are connecting to. This will ensure that you do not have any erroneous home runs in your project. Figure 14.19a shows a wire moved from between two fixtures, and Figure 14.19b shows it connected to another fixture by dragging the connection point grip.

The type of wire that is created by using the Convert To Wire button is the last type of wire that was drawn in your project, or the default wire type is used if none has been manually drawn. You can change a wire type by selecting it and choosing a new type from the Type Selector in the Properties palette. You can change all the wires for a circuit by editing the properties of that circuit.

Figure 14.19. (a) Wire connected between two fixtures; (b) the result of dragging the connection point to another fixture

When you select a device or fixture that has a circuit, the Electrical Circuits contextual tab appears with tools for editing and managing the circuit. This tab is similar to the tab that appears when you create a circuit. If the device you have selected contains multiple connectors, the System Selector drop-down allows you to choose which circuit you would like to edit.

Click the Edit Circuit button to add or remove elements from the circuit. When you click the Edit Circuit button, the Edit Circuit contextual tab appears, and all items that are not part of the circuit turn to halftone in the drawing area, including annotation and wiring, while elements of the circuit remain as normally displayed. The Add To Circuit button is automatically selected when you click the Edit Circuit button. You can click any device or fixture in your view to add it to the circuit. You can also select devices or fixtures from other locations if you have multiple views of the model open. If you select an element that does not have a connector that matches the distribution system of your circuit, you will receive a warning dialog box, and the element will not be added to the circuit, as shown in Figure 14.20 where the receptacle was selected to be added to the lighting circuit.

Figure 14.20. Circuit warning

When you select a device or fixture with a connector that matches the distribution system of the circuit you are adding to, the display of the device or fixture changes from halftone to normal. You can click the Remove From Circuit button on the Edit Circuit contextual tab to remove items from the circuit. Once you have finished adding or removing items from a circuit, click the Finish Editing Circuit button to complete your changes. If you have wiring drawn to show items on a circuit and you remove some of the items, Revit MEP will not remove the wiring.

Another method for adding or removing objects is to select the object and right-click its connector grip. Select a device or fixture to add to a circuit, and right-click the connector grip. If you do not have your cursor over the connector grip when you right-click, you will get a menu with tools for visibility control. Right-clicking the connector will give you the same menu but with additional tools for circuiting. Select the Add To Circuit option from the menu, and click any device or fixture that is part of the circuit you want to connect to. You also have the option to create a new circuit from the right-click menu.

When you select a element on the circuit that you want to add your device or fixture to, you will be given the option to automatically generate wiring to show the added device as part of the circuit.

Selecting a device that is already part of a circuit and right-clicking its connector will give you a menu with the option to remove the element from the circuit. Removing a fixture or device from a circuit will not delete any wiring shown to it, but the wiring may change depending on the location of the removed element in the circuit. Figure 14.21 shows how wiring can be affected when a device is removed from a circuit. The receptacle in the lower-right corner was removed from the circuit. The receptacle in the upper-right corner is still a part of the circuit, so the wiring has changed to a home run. The wire from the unconnected receptacle to the one on the left has changed to a home run also, because it is not part of the circuit but has a device downstream that is part of the circuit. In any case, removing elements from a circuit will usually require some cleanup of the wiring.

Figure 14.21. Wire changed by removing a device from a circuit

The workflow for creating circuits can be easily learned and can become second nature to your design and modeling processes. Practice creating circuits by doing the following:

It is not necessary to only use the automatic wiring capability of Revit MEP 2011 to create the wiring for your circuits. You can quickly and easily draw wires manually. In some cases, it may be easier to draw the wire than to make adjustments to automatically generated wiring.

To draw wiring, click the Wire button located on the Home tab. The bottom half of the button is a drop-down with options for the style of wire you can draw. You can draw arc, chamfer, or spline wires. These are only options for how the wire is drawn and have nothing to do with wire types or the electrical properties of the circuit or devices. Once you have selected a wiring style, you can choose a wire type from the Type Selector in the Properties palette. You can use the Tag On Placement button on the contextual tab to place a tag on the wire as you draw it.

You can draw wire anywhere in your plan views, so it is important that you snap to the component geometry of the elements you are showing the wire for. If you draw a wire between two symbols, it may appear that they are connected by the wire, but if the wire is not attached" to the device, then when the devices move, the wire will not move with them. To ensure that your wire is connected to an element, you need to snap to a point on the component geometry, not the symbol that represents the component. As long as your cursor is over some part of the component when you start your wire, the wire will connect to the component at the electrical connector. Figure 14.22a shows a wire being drawn from a mechanical unit by clicking the edge of the unit, and Figure 14.22b shows the wire attaching to the electrical connector of the unit.

The unit shown in Figure 14.22 has an electrical connector so the equipment connection symbol on the electrical drawing does not have a connector or any electrical properties. The wiring to this unit can be modified to be shown from the disconnect switch symbol while maintaining its connection to the unit, as shown in Figure 14.23.

Arc- and chamfer-style wires are drawn by clicking a start point for the wire, a middle point, and an end point. To draw wire between two components, start your wire at one component, click somewhere between the two items, and click the second component to end the wire. Spline style wires allow you to click several times between elements. To draw a wire home run, you simply start a wire at the connector of a device or fixture and leave the other end of the wire unconnected. If the component you draw from is assigned to a circuit, the wire will show an arrowhead, indicating a home run. If the component is not assigned to a circuit, the wire will display without an arrowhead until the element has been assigned to a circuit.

Figure 14.22. (a) Drawing a wire from a unit; (b) the wire connected to the unit at the electrical connector

Drawing a wire between components does not mean that they are on the same circuit. If you draw a wire from a component that is on a circuit to another component that is not on a circuit, the second component will not be added to the circuit. You can draw wire between components that are not on the same circuit, creating a multicircuit run of wiring. A home run wire will be displayed between components that are on different circuits, as shown in Figure 14.24.

Figure 14.23. Modified wiregraphics

Figure 14.24. Multicircuit run of wiring

You can show multiple home runs from a single component that has multiple connectors. If you use the automatic wire option, it will work only for the first circuit that you create. You will have to draw the second home run manually.

You can use a wire tag to confirm that the home runs are not connected to the same connector, as shown in Figure 14.25.

Figure 14.25. Multiple home runs from a single device

Using a filter to control the display of wires in your project is an effective method for distinguishing between different wire types. As mentioned earlier, creating wire types in the electrical settings of your project makes it easy to isolate specific wires for visibility control. This allows you to show wire such as underground, overhead, or low-voltage wire in the same view and be able to identify the different types.

To create a filter for wires, click the Filters button located on the Graphics panel of the View tab. In the Filters dialog box, select the New button in the upper-left corner. Give the filter a name that clearly identifies the purpose of the filter or what types of elements it applies to. In the Categories section of the dialog box, select the Wires box to apply the filter to wires. In the Filter Rules section of the dialog box, choose the Type Name parameter from the Filter By drop-down list. Set the condition to Equals in the second drop-down list, and choose the name of the wire type that you want to apply the filter to in the third drop-down list. This creates a filter that affects only wires with the type name chosen, as shown in Figure 14.26.

Figure 14.26. Filter settings for a wire-type filter

To apply the filter to your view, access the Visibility/Graphic Overrides settings for the view, and select the Filters tab. Click the Add button in the lower-left corner, and choose the filter you created for the wires from the Add Filters dialog box. Click the Override button in the Lines column for the filter. Set the Weight, Color, or Pattern overrides for the filter to display the wire as desired. Figure 14.27 shows floor boxes with underground wire in the same view as receptacles with wire as it is normally displayed.

Figure 14.27. Different wire types displayed in the same view using a filter

To access the properties of a circuit, select an element connected to it, and select the Electrical Circuits contextual tab. If the selected component has multiple circuited connectors, you can choose which circuit properties to access by selecting the circuit from the System Selector drop-down. The properties of the circuit are displayed in the Properties palette. Click the Properties button on the ribbon to access the Properties palette. Because most of the data comes from the electrical characteristics of the connector and the distribution system, many of the parameters of the circuit are not editable and grayed out. Revit takes the load information from the components on the circuit and calculates the apparent load and current as well as the voltage drop and wire size. You can change the type of wire used for the circuit by editing the Wire Type parameter. Changing this parameter will not change the wire types of the wires you have drawn for the circuit; it only defines the type of wire used for calculations.

You can change the Load Name parameter to give the circuit a more descriptive name that will appear in the panel. When you are creating a circuit for components and the load exceeds 80 percent of the circuit breaker rating, Revit MEP 2011 will give you a warning. It does not prevent you from overloading a circuit, however. The default breaker size for circuits is 20 amps. The Rating parameter indicates the circuit breaker size for the circuit and can be changed to meet the requirements of your circuit.

You can access the properties of a wire in the Properties palette when you select a wire in the model. Clicking the Edit Type button in the Properties palette opens the Type Properties dialog box, which displays the parameters for the wire as defined in the electrical settings for the project. You can add information such as a description or type mark to the wire type.

The instance properties of the wire control the display of tick marks and the number of conductors for the circuit. There are three options for the Tick Marks parameter:

The number of conductors can be increased or decreased by editing the values of the Hot, Neutral, and Ground Conductors parameters. You can change the number of hot conductors using the + and – editing grips that appear when you select a wire. The location of the tick marks on a wire can be changed by clicking the solid blue dot that appears at the center of the tick marks when a wire is selected.

In the instance properties of a panel, you can provide information about it that will appear in the panel schedule. New to Revit MEP 2011 are the Schedule Header Notes and Schedule Footer Notes parameters. Click the Edit button in these parameters to add notes to the header or footer of a panel schedule. The Mains parameter is for indicating the size of the main circuit breaker and does not affect any load calculations. The Max #1 Pole Breakers parameter allows you to assign the number of poles in the panel. You can also indicate the short-circuit rating, enclosure type, and any modifications by editing the respective parameters.

You can define how the circuit tags will display in your drawings by editing the Circuit Naming, Circuit Prefix, and Circuit Prefix Separator parameters. The standard wire tag is a label that displays the circuit number. There are three options for circuit naming:

Figure 14.28 shows three circuits to panels that use different naming conventions. The panel for the circuit in the lower left uses the Panel Name option with a hyphen as a separator. The panel for the receptacle on circuit 2 uses the Standard circuit-naming option, and the panel for the circuit on the right uses a prefix PWR" and a slash as a separator.

When you select a panel, the Modify | Electrical Equipment contextual tab appears. The Edit Panel Schedule button on this tab allows you to make changes to where the circuits are connected in the panel. In this view of the panel, you can change the fonts used in the cells to match your standards. Select a cell or multiple cells, and right-click to change the font. In the Edit Font dialog box, you can set the text size, font style, and color, as shown in Figure 14.29.

You can change the name of a circuit by simply editing the value in the cell. This will update the value of the Load Name parameter of the circuit. Once you have made changes to circuit names, the Update Names button becomes active when you select a cell that has been edited. Clicking this button will return the circuit name to the default, which includes the load classification name and the location of the object.

You can change the size of the circuit breaker for a circuit by editing the cell in the panel schedule. This will update the value of the Rating parameter of the circuit. If you edit the breaker to a size that causes the circuit to be overloaded, you will receive a warning dialog box.

Figure 14.28. Wire tags using different circuit naming options

Figure 14.29. Edit Font dialog box for a panel schedule

To balance the loads in a panel, you can click the Rebalance Loads button on the ribbon. This will move circuits around in the panel to achieve the most balanced configuration possible across the phases. This may cause unwanted results, so use caution with this feature. For example, you may have a multicircuit run that occupies circuits 1, 3, and 5, but after rebalancing the loads, the circuits end up as 1, 4, and 18. It may also move multipole circuits to locations where they normally would not be placed. To avoid this scenario, you can use the Group/Ungroup button that becomes active when you select multiple circuits. This will maintain the order of the circuits and move them as a single unit. Grouped circuits are indicated with a blue dashed box around them. Selecting any cell within a group of circuits and clicking the Group/Ungroup button will remove all the circuits from the group, not just the selected cell or cells.

You do have the option to relocate circuits manually instead. To change the position of a circuit in a panel, click the circuit number. This will activate the move buttons on the Circuits panel of the tab. You can move the circuit up or down the side of the panel it is on. When you move a circuit up or down to a space that already contains a circuit, the two circuits will change places. Circuits can also be moved from one side of the panel to the other. As with moving up or down, moving a circuit to an occupied space on the other side of the panel will cause the two circuits to swap locations.

When you select a panel for a circuit, Revit MEP 2011 finds the first available circuit in the panel and places the circuit there. Spares and spaces can be added to occupy circuits in the panel. Because you cannot choose the circuit number for a circuit when it is created, when you add a circuit to the panel, the circuits occupied by spaces or spares will not be used.

To insert a spare or space, select an unoccupied circuit number, and click the Assign Spare or Assign Space button on the Circuits panel of the tab. A light brown background is applied to the cells for the circuit number. This background is a visual indication that the circuit is locked. A locked circuit cannot be moved in the panel. You can edit the name of a locked circuit and also change its breaker size. Any occupied circuit in the panel can be locked using the Lock/Unlock button on the Circuits panel of the tab. The only way to remove a spare or space is to select it and click the Remove Spare/Space button on the Circuits panel of the tab.

Circuits can be created for any of the categories of electrical systems. Wire types can be created to distinguish these systems visually if wiring is shown. The panels for these systems can be used to manage the circuit locations. You can create panel schedule templates for the various types of panel schedules that you use in your projects. Figure 14.30 shows the Edit Circuits dialog box for a telephone terminal block used as the panel for the telephone circuits in a project.

Figure 14.30. Telephone circuits

Although telephone wiring is not normally shown on a typical building project, creating these systems provides you with information that can help in making design decisions. This type of information could later be modified to represent the as-built conditions of your project, which could then be useful for facilities maintenance. It is about putting the I in your BIM project.

You can create schedules for panels and circuits that can be used to extract information about your project. Organizing the data contained in your project regarding electrical loads can help you make design decisions and keep your design coordinated with other disciplines. Schedules can also be created to supplement the panel schedules generated by Revit MEP.

Circuits hold a host of useful data that can be scheduled for project coordination and design. Figure 14.32 shows a schedule of electrical circuits that displays information that can be used to verify circuit locations and length, breaker size, and load, as well as wire size. This type of schedule may be useful because you can display and manage information about the circuits that may not appear in your panel schedules. Having this information in a schedule makes it easy to check your design and make any necessary changes.

Figure 14.32. Electrical circuits schedule