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Understanding Parameters Revit mep

It takes a good understanding of the parameters besides height and width (or radius) before you can set up complex air systems. There are 14 parameters associated with a duct connector when its System Type is not set to Fitting. Not all of the 14 are active all the time (see Figure 9.7).

Figure 9.7
Parameters for
duct connection
If the connector System Type is set to Fitting, the connector has only six parameters. Revit MEP has several system types available for duct connections that facilitate system creation and view filters within a project (see Figure 9.8).
Starting at the top, here is an explanation of each duct connector parameter as shown in Figure 9.7:
Flow Factor This parameter determines the percentage of the system flow that will be seen by the connector. It is available only when Flow Configuration is set to System. It is useful when using multiple devices, each of which is sized for part load.
Loss Coefficient Available only when Loss Method is set to Coefficient, this parameter is used in conjunction with the Flow parameter to determine the pressure drop.
Flow Configuration This parameter determines how the connector flow will be calculated.
Calculated This setting calculates airflow downstream of the connection and sets the Flow parameter to the sum of those flows. It is particularly useful for VAV boxes.
Preset No calculation is needed, and airflow is set to the Flow parameter.
System This setting is similar to Calculated, but the flow factor comes into play. It is best used for splitting the total system airflow between air handlers.
Flow Direction The flow direction can be In, Out, or Bidirectional. This direction is referring to the direction air is moving relative to the connector. For example, a supply air diffuser
should be set to In because the air is flowing into the connection. An exhaust grille would be set to Out because air is coming out of the connection (to the system).
System Type Here, the most appropriate system type is chosen for the application. Supply Air, Return Air, and Exhaust Air are all pretty self-explanatory, but they also have other uses.
Supply Air Air that is to be supplied to a space can also be used to model outside air, which is also known as air to be delivered to a space or air handler.
Return Air Air that is being returned from the space back into the system is called return air. It can also be used in place of relief air, but exhaust makes a little better candidate.
Exhaust Air Air that is destined to leave the space as well as the system is called exhaust air. This is the best option for modeling relief air.
Other Air Other Air seems like a logical candidate for relief air or outside air; however, systems cannot be made with Other Air.

Figure 9.8
System Types for
duct connections
Fitting The Fitting system type is merely a pass-through connection; there is no effect on the airflow or definition of the system.
Global Global connections also cannot be made into systems on their own; however, they inherit the characteristics of whatever system connects to them. Fans are a good example of equipment that may use global connections.
Loss Method Not Defined, Coefficient, or Specific Loss are the options here, and Coefficient
and Specific Loss each activate another parameter. Specific Loss should be used where the loss is known from a catalog or cut sheet. The pressure loss is taken literally as the entered value for Pressure Drop.
Pressure Drop This can be entered as a static value or linked to a family parameter. Units are handled in the Project Units dialog box (Manage Project Units).
Flow Values for the flow associated with the connector are dependent on flow
Shape The Shape settings of Rectangular or Round determine which dimension parameters are active and the shape of the duct that will connect to the connector.
Height Height is simply a dimension of the connector. It can be linked to a family parameter.
Width Width is simply a dimension of the connector. It can be linked to a family parameter.
Radius Radius is similar to Height and Width; however, be careful to use the radius and not the diameter when linking to a family parameter.
Utility This indicates whether the connector is exported as a site utility connection point to an Autodesk Exchange file (ADSK).
Connector Description The option to assign a name to connectors shows up primarily when using the Connect To feature. It also appears when connection points are in the same vertical plane. It is a good practice to give your connectors a description so that they can be easily identified in families with multiple connectors.

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