The Delete Equipment from Database command is used to delete equipment that is in the database but not on a drawing. Equipment that is on a drawing can be deleted using the standard CAD ERASE command. Equipment not on the drawing can only be erased using the Delete Equipment from Database command.
To delete equipment that is in the database, go to
Ribbon: DM Electrical->Devices-> 
Delete Equipment from Database
Pulldown Menu: DM Electrical->Equipment->Delete Equipment from Database
Delete Equipment from Database Dialog Box
Group: A list of the equipment groups in the project. The equipment listed in the Equipment list are all part of the selected group. See the Equipment Project Groups section for more information.
Equipment: A list of all of the equipment in the database that is not on a drawing. You can select multiple items in the list using the SHIFT or CTRL keys.
Delete: Press this button to delete the selected equipment from the database. A Design Master Electrical dialog box will appear asking you to confirm the deletion.