Since HVAC fittings can be comprised of many legs, each with a different shape and size, PE-HVAC has a more complicated way of passing information about the duct layout into Eden than Piping uses. Therefore, PE-HVAC has defined the global variables SHAPE_1 through SHAPE_10, WIDTH_1 through WIDTH_10, and DEPTH_1 through DEPTH_10 for you to access in the Eden symbol definition. Automated placement sets these variables up in the following manner:
SHAPE_1, WIDTH_1, and DEPTH_1 contain information on the A dimension.
SHAPE_2 through SHAPE_10, WIDTH_2 through WIDTH_10, and DEPTH_2 through DEPTH_10 contain information on the other ducts at the active place point. For example, a cross layout would have the information passed in as follows:
These conventions are forced upon any fitting definition being executed by the Model command. The Place Fitting command is less restrictive since you are allowed to set up the variables by hand, but Intergraph Corporation strongly recommends using the same convention if at all possible to keep things consistent for you.
PE-HVAC also defines four other global variables for fitting definitions to access: BEND_ANGLE, BEND_RATIO, TRANSITION_LENGTH, and TRANSITION_ANGLE. During modeling, BEND_ANGLE is set to the angle of the layout location, while BEND_RATIO and TRANSITION_ANGLE are set to values retrieved from the service default table. TRANSITION_LENGTH is not set. The Place Fitting command allows you to override these values and set them manually.
For device symbols definitions, the global variables MANUFACTURER, MODEL_NO, BOX_WIDTH, BOX_DEPTH and BOX_LENGTH have been defined. All of these variables are set to the values currently displayed on the Place Device form.
This means that BOX_LENGTH is not set for diffusers, grilles, or registers.
Intergraph Corporation suggests using the manufacturer and model number to format a table name from which any other dimensions needed to draw the symbol can be retrieved.