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Duct Sizing Methods, Specifying a Calculation Method for Duct Sizing

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Duct Sizing Methods Duct sizes are calculated using either the equal friction method or constant velocity method. For more information, see Specifying a Calculation Method for Duct Sizing on page 182. The calculations for duct friction losses are based on the Darcy and Altshul-Tsal equations described in the 2001 ASHRAE Fundamentals Handbook, Chapter 34, as follows: ■ Duct friction loss for round, rectangular, and oval ducts is calculated using equation 19. ■ Duct friction factor for round, rectangular, and oval ducts is calculated using equation 21. ■ Reynolds Number is calculated using equation 23. ■ Equivalent round duct diameter for a rectangular duct is calculated using equation 25. ■ Equivalent round duct diameter for a flat oval duct is calculated using equations 26, 27, and 28. ■ To size friction for the rectangular or oval duct, the calculations use the equivalent round duct diameter and its velocity. ■ The dialogs for Add Ducts and Modify Duct list the actual velocity for the selected CFM and duct size, not the velocity used in the duct friction calculations. The actual velocity is displayed for duct fitting and acoustical analysis. ■ When a CFM is not displayed in the dialogs for Add Ducts or Modify Duct, the friction or velocity values shown are the values specified in the Design Parameters for the Duct System Definition. To specify design parameters for the Duct System Definition, see Specifying a Calculation Method for Duct Sizing on page 182. The Add Ducts dialog shows an asterisk next to the Velocity field to indicate that the constant velocity method was used to calculate duct size. The Modify Duct dialog shows the fixed parameter value for velocity that was used to calculate duct size. Duct sizes are calculated based on the flow values assigned to all outlet devices detected in the system. For more information on assigning flow values, see Configuring Mechanical Parts for Analysis on page 196. 170 | Chapter 6 Drawing HVAC Systems

Section	Page
Contents	3
New Features in This Release	19
New Features for Getting Started	19
New Features for Drawing Electrical Systems	19
New Features for Drawing Piping Systems	20
New Features for Drawing Radiant Heating Systems	20
New Features for Customizing Catalogs	21
New Features for Customizing Display	21
New Features for Building Systems	21
Moving from AutoCAD to AutoCAD MEP	23
AutoCAD to AutoCAD MEP Task Comparisons	23
Creating Building Systems	24
AutoCAD MEP Workspaces	24
Insertion Tools	25
Layer Keying	25
Modifying Building Systems	25
Associative Movement	25
Grips	26
Snaps	29
Automating Design Tasks	30
Domain-Specific Ribbons	30
Auto Layout	30
Interference Detection	30
Connectivity Checks	31
Working With Sizing and Calculation Tools	31
Sizing Tools	31
Electrical Circuit Manager	32
Plumbing Tools	32
Pipe Routing Preferences	32
Solution Tips	33
Creating Accurate Construction Documents	33
Section Views	33
Tagging	34
Labeling and Annotation Scaling	35
Layout Symbols	36
Project Management	37
Schedules	37
Leveraging AutoCAD Knowledge in AutoCAD MEP	37
Working with AutoCAD Commands in AutoCAD MEP	38
ALIGN	38
ARRAY	38
BREAK	39
CHAMFER	39
COPY	39
ERASE	39
EXPLODE	40
EXTEND	40
FILLET	40
JOIN	41
LENGTHEN	41
MATCHPROP	42
MIRROR	42
MOVE	42
OFFSET	43
PURGE	43
ROTATE and ROTATE3D	43
SCALE	44
STRETCH	44
TRIM	44
Help Resources	44
Getting Started	45
About AutoCAD MEP	45
AutoCAD MEP Workflow	46
Intelligent Objects	46
Location of Part Catalogs	47
Analysis Tools	48
Project Management Tools	48
Contacting Autodesk	48
Getting Help	49
Guides	49
Tutorials	50
Training	50
Classes	50
Courseware	50
E-Learning	50
Certification	51
Discussion Groups	51
Additional Resources	51
Updating AutoCAD MEP	51
The AutoCAD MEP 2010 Drawing Domain	51
Workspace Fundamentals	53
Default Workspaces in AutoCAD MEP	54
Creating Workspaces	55
Switching Workspaces	55
Workspace Settings	55
Workspace Components	56
Ribbon	57
Displaying the Ribbon	57
Using the Ribbon	57
Locating Commands in the Workspace	59
Static Ribbon Tabs	61
Home Tab	61
Floating View Panel	62
Insert Tab	62
Annotate Tab	63
Analyze Tab	63
View Tab	63
Manage Tab	64
Contextual Tabs	65
Application Menu	66
Accessing the Application Menu	67
Using the Application Menu to Locate Commands	67
Displaying Recently Opened Documents in the Application Menu	68
Displaying Currently Open Documents in the Application Menu	69
Changing the Number of Recent Files and Actions in the Application Menu	69
Quick Access Toolbar	69
Context Menus	70
Tool Palettes	71
Properties Palette	71
Drawing Status Bar	71
Showing and Hiding Commands on the Drawing Status Bar	73
Showing and Hiding the Drawing Status Bar	73
Command Line	73
Application Status Bar	74
Showing and Hiding Commands on the Application Status Bar	76
Project Navigator Palette	76
Finding Information in AutoCAD MEP	77
InfoCenter Toolbar	77
Help Menu	78
Communication Center	78
F1 Context Help	78
Tooltips	78
Command Tooltips	78
Controlling the Display of Command Tooltips	79
Dialog and Palette Tooltips	79
Object Rollover Tooltips	80
Property Palette Tooltips	80
Thumbnail (Preview) Tooltips	81
Solution Tips	82
Object Grip Tooltips	83
Working in Model Space and Paper Space	84
Customizing the Display of MEP Objects	84
Using Custom Display	85
Drawing Essentials	87
Drawing Preferences	87
About Layout Preferences	87
Initialization Preferences	88
Specifying Part Catalogs and Style-Based Content Locations	88
Layout Rules	89
Part Connection Rules	89
Configuring Connection Test Rules	90
Standard and Custom Part Sizes	91
Configuring Part Selection	91
Defining System Elevations	91
Configuring Tooltip Settings	92
AutoCAD MEP Snaps	93
Configuring AutoCAD MEP Snaps	93
Mechanical, Electrical, and Plumbing Equipment in Building Systems	94
Working with Catalog-Based Content	97
How Catalog Parts are Stored and Referenced	98
How Catalog Parts Are Defined	99
Part Sizes	100
Default Parts	101
Importing a Building Component into AutoCAD MEP 2010	102
Working with Style-Based Content	103
How Style-Based Content is Stored and Referenced	103
Orthographic and Isometric Views of Style-Based Content	104
Working with Tool Palettes	105
Opening the Tool Palette Set	106
Changing the Active Group in the Tool Palette Set	106
Modifying the Appearance of the Tool Palette Set	107
Docking the Tool Palette Set	107
Hiding the Tool Palette Set	107
Adjusting the Transparency of the Tool Palette Set	107
Modifying the Appearance of Tools	108
Working with the Properties Palette	109
Opening the Properties Palette	109
Modifying Object Properties Using the Properties Palette	109
Modifying Display Properties Using the Properties Palette	110
Modifying the Appearance of the Properties Palette	110
Docking the Properties Palette	110
Hiding the Properties Palette	110
Adjusting the Transparency of the Properties Palette	110
Working with Systems	111
About System Groups	112
Creating Systems	113
Specifying the Design Rules of a System	115
Specifying the Rise/Drop Style of a System	116
Specifying the Display Properties of a System	117
Attaching Notes and Files to a System	118
Copying Systems Between Drawings	118
Purging Systems	119
Selecting a Display Configuration	120
Essentials of Objects	121
Object Types	122
Matching Object Properties	124
Working with Connectors	125
Working with Anchors	126
Attaching Objects with a Curve Anchor	127
Attaching Objects with a System Anchor	128
Attaching Objects with a Reference Anchor	128
Rotating Objects Attached with Curve Anchors	128
Releasing Anchored Objects	129
Part Anchors	129
Using the Compass	130
Customizing the Compass Display	132
Designing with Dynamic Input and Grips	132
Dynamic Input	133
Grip Tooltips	134
Grip Constraints	134
Trigger Grips	134
Grip Editing Modes	135
Drafting with Flow Direction	136
Selecting Similar Objects	137
Selecting MEP Objects	138
Regenerating an AutoCAD MEP Model	138
Viewing Part Properties	139
Basic Part Information	139
System Assignments for Parts and Connectors	140
Part Styles	142
Part Property Details	143
Part Location	145
Working with Projects	147
Working with Drawing Management Projects	147
Establishing Project Standards	148
AutoCAD MEP Layer Standards	150
Layer Standards Overview	150
Layer Standards	150
Layer Key Styles and Layer Keys	151
Layer Standards Drawing	151
Layer Properties Manager	151
Specifying a Layer Standard and a Layer Key Style	152
Accessing Layer Key Styles and Layer Keys	152
AutoCAD MEP Displays	152
Display System Structure	153
Display Representations	155
Display Sets	157
Display Configurations	157
Hierarchy of Display Control	159
Managing Display Settings During Project Setup	159
Specifying Default Display Settings	160
Applying System-Level Overrides	161
Applying Style-Level Overrides	161
Configuring Display Settings During Design	161
Display of Objects Based on Elevation	162
Workflow for Displaying Objects Based on Elevation	164
Enabling the Elevation-Based Display Components	165
Specifying the Cut Plane and Display Range for a Display Configuration	165
Configuring Elevation-Based Display Components	167
Modifying Elevation-Based Display Components on the Properties Palette	167
Overriding the Cut Plane	168
Display of Crossing Objects in 2-Line Plan Views	169
Configuring the Display of a Gap Between Crossing Objects	169
Modifying Hidden Lines for Objects	170
Display of Center Lines on Ducts	170
Display of Objects by Classification	172
Adding Custom Graphics as a Display Component	173
Troubleshooting Object Display	173
AutoCAD MEP Templates	174
Default Drawing Templates	174
Creating a Custom Template from a Template or Drawing	175
Creating a Custom Template	176
Working with Referenced Drawings	176
Attaching or Overlaying Xrefs	177
Reloading Xrefs	178
Clipping Xrefs	178
Changing the Display Configurations of Xrefs	179
Drawing HVAC Systems	181
HVAC System Workflow	181
Mechanical System Workflow	182
Duct System Workflow	182
Flow Annotation	183
Duct	184
Flexible Duct Runs	185
Auto-layout	186
HVAC System Settings	186
Duct Fitting Vanes	186
Takeoff Position	187
Duct Sizing Methods and Tools	187
Duct Sizing Using Third Party Tools	190
Duct System Snaps	190
Grips	190
Configuring Duct System Settings	192
Configuring Duct Layout Preferences	192
Configuring Justification for Duct Insertion	192
Configuring Sloped Duct	193
Breaking Duct at Even Intervals	194
Adding Lining or Insulation	194
Adding Labels or Flow Arrows to Ducts	195
Configuring the Display of Turning Vanes and Flanges	196
Configuring Flexible Duct Preferences	197
Specifying Default Parts for Layout	198
Configuring Duct Connections	198
Configuring Duct System Definitions	199
Creating a Duct System Definition	199
Specifying a Calculation Method for Duct Sizing	200
Configuring the Display of Ducts and Fittings	201
Using Spaces for Load Analysis	201
Configuring Space Styles	201
Viewing Classification Settings	203
Configuring Zone Styles	203
Adding Spaces to a Floor Plan	203
Adding Engineering Data to Spaces	205
Attaching Property Sets to Zones	207
Attaching Spaces to Zones	207
Exporting Zones for Load Analysis	208
Reviewing Spaces and Zones	209
Importing Load Analysis Results	210
Using Space and Zone Calculated Data	211
Creating a Duct System	212
Adding HVAC Equipment	212
Adding HVAC Equipment	213
Adding Parts In-Line to Ducts	213
Configuring Mechanical Parts for Analysis	214
Adding Duct	214
Drawing a Duct Run	214
Starting a Run From Existing Duct	217
Connecting a Duct Run to Equipment	218
Adding Duct Using Grips	218
Drawing a Vertical Duct Run	219
Drawing 1-Line Duct	219
Calculating Duct Sizes for a Duct System	221
Adding a Duct Fitting Manually	223
Drawing Flexible Duct	224
Adding a Parallel Duct Run	225
Offsetting Duct from Existing Geometry	226
Drawing Sloped Duct	226
Using the Elevation Lock	226
Connecting Ducts Through Referenced Drawings	227
Adding a Takeoff to a Duct	229
Converting a Line to Duct	231
Converting a Polyline to Flexible Duct	231
Adding Turning Vanes to Fittings	232
Creating a Custom Duct Fitting	233
Using the Part Size Not Found Dialog	235
Annotating a Duct System	236
Adding a Label to a Duct	236
Adding a Hatching Pattern to Identify a Duct System	237
Modifying a Duct System	237
About Associative Movement	237
Selecting Components	237
Modifying Components Using Grips	238
Moving Duct Components	239
Modifying the Elevation of HVAC Parts and Ducts	240
Modifying the Length of Ducts	243
Rotating Duct Components	246
Modifying HVAC Equipment	248
Modifying HVAC MvPart Location	248
Modifying HVAC Parts	249
Changing a Part to Match Another Part	250
Modifying the Flow Value Assigned to a Part	250
Modifying the System Assigned to a Part Connection	250
Modifying Duct	250
Modifying the Size or Shape of a Duct	251
Modifying Duct Using AutoCAD Commands	252
Breaking or Merging Duct	252
Breaking a Duct Segment	252
Breaking and Merging Duct Segments	252
Locking the Size of a Duct or Fitting	253
Modifying the System Assigned to a Duct	253
Modifying a Duct Fitting	253
Modifying the Layout of Flexible Duct	254
Moving an Off-Center Takeoff	255
Modifying a Custom Fitting	255
Modifying Turning Vanes	256
Modifying Insulation or Lining	256
Checking Connectivity in a Duct System	257
Modifying Annotation	257
Modifying a Label	257
Calculating Duct Sizes Using External Tools	259
Specifying ASHRAE Fitting Types	260
Exporting Duct System Data	260
Importing Optimized System Data	262
Resizing a System	262
Creating Duct System Construction Documents	263
Drawing Piping Systems	265
Pipe Systems Overview	265
Workflow for Designing a Pipe System	265
Associative Movement	266
Movement of a Pipe Segment	266
Movement of a Pipe MvPart	267
Routing Preferences	268
Auto Layout	270
Routing Solutions	272
Sloped Piping	274
Pipe System Definitions	275
Pipe System Displays	276
Display Configurations in AutoCAD MEP	276
1-Line Display	277
Graphical 1-Line Display	278
2-Line Display	278
Straight Centerline Display of Elbows	279
Placeholder Parts	279
Pipe Parts Catalog	280
Pipe Connections	282
Pipe Connectors	282
Connector Assignments	283
Connection Types for Pipe and Pipe Fittings	284
Male-Female Fittings	285
Connector Engagement Length	285
Angle of Deflection (Fitting Tolerance)	285
Pipe Joints	286
Pipe Length	286
Pipe Snaps	288
Pipe Elevation Lock	288
Pipe Grips	289
Grips for Adding to a Pipe Run	290
Grips for Modifying a Pipe Run	291
Location Grips	291
Elevation Grips	292
Flip and Rotate Grips	293
Lengthen Grips	294
Configuring Pipe System Settings	297
Configuring Routing Preferences	297
Creating or Copying a Routing Preference	297
Configuring Properties for a Routing Preference	298
Configuring Size Ranges	298
Deleting a Routing Preference	299
Configuring System Definitions	299
Creating a System Definition	299
Configuring System Definitions for 1-Line, 2-Line, or Single Line Graphics	300
Configuring Graphics for Single Line Pipe Display	301
Configuring the Straight Centerline Display of Elbows	302
Creating a Piping System	303
Adding Pipe Equipment	303
Placing a Pipe MvPart in a Drawing	303
Adding Parts In-Line to Pipe	304
Adding Pipe	304
Pipe Properties Palette (Add Mode)	304
Basic Properties	305
Advanced Properties	307
Adding Pipe Using the Tool Palette	309
Configuring Basic Properties for Pipe	311
Configuring Pipe Layout Preferences	311
General Preferences	312
Connection Assignments	314
Configuring Justification for Pipe Insertion	315
Specifying Cut Length	315
Drawing a Pipe Run	316
Connecting to Existing Pipe	316
Connecting a Pipe Run to an MvPart	318
Adding a Vertical Segment to a Pipe Run	319
Adding Pipe Using Grips	320
Manually Specifying Parts During Layout	321
Choosing a Part	321
Overriding a Fitting	323
Multiple Parts Found	323
Using Routing Solutions to Connect Objects	324
Adding a Pipe Fitting Manually	324
Creating a Custom Pipe Fitting	325
Drawing Sloped Piping	326
Drawing a Flexible Pipe Run	328
Viewing Connection Details	329
Adding a Parallel Pipe Run Using Offsets	331
Offsetting Pipe from Existing Geometry	332
Locking Pipe Elevation During Drawing	333
Adding a Takeoff to a Pipe	333
Adding Insulation to Pipe	335
Adding Labels or Flow Arrows to Pipe	335
Converting a Polyline to Flexible Pipe	336
Modifying a Piping System	336
Selecting or Filtering Objects	336
Filtering Pipe Objects with Quick Select	337
Filtering by Pipe Part Type	337
Modifying Components Using Grips	338
Moving Pipe Components Using Location Grips	338
Modifying the Elevation of Pipe Components	338
Rotating Pipe Components	339
Modifying the Length of a Pipe Segment	340
Modifying Pipe Equipment	340
Modifying the Location or Elevation of an MvPart	340
Modifying the Size or Elevation of an MvPart	341
Matching an MvPart of One Type to Another	342
Modifying the K-Factor	342
Modifying the System for an MvPart Connector	342
Modifying Pipe	342
Pipe Properties Palette (Modify Mode)	343
Basic Properties	343
Advanced Properties	344
Modifying the Routing Preference and Nominal Size	346
Modifying the Pipe or Fitting Location	346
Modifying Connected Objects Along a Pipe Run	347
Breaking or Merging Pipe Segments	347
Locking the Size of a Pipe or Fitting	348
Modifying the System Assigned to a Pipe	349
Modifying a Pipe Fitting	349
Modifying the Layout of a Flexible Pipe	349
Modifying Insulation on a Pipe or Fitting	350
Checking Connectivity in a Pipe System	350
Modifying a Label or Flow Arrow	350
Drawing Radiant Heating Systems	353
Radiant Heating Systems Overview	353
Creating Radiator Parts	354
Using a Calculation Program to Add Radiators	355
Adding Radiators Using Calculated Data	356
Rules About Updating Existing Radiators	357
Exporting Drawing Information for Analysis	358
Designing Radiant Heating Systems	358
Adding a Radiator MvPart	359
Modifying a Radiator MvPart	361
Radiator Valves	361
Adding a Radiator Valve	361
Modifying a Radiator Valve	362
Moving a Radiator Valve	362
Connecting MvParts Using Alignment Grips	363
Creating Pipe Runs for Radiators	364
Adding Parallel Pipes to a Radiant Heating System	365
Correcting a Parallel Pipe Routing Conflict	368
Connecting Multiple Radiators to Parallel Pipes	368
Correcting a Radiator Connection Failure	369

Match case Limit results 1 per page

Duct Sizing Methods

Duct sizes are calculated using either the equal friction method or constant velocity method. For more

information, see

Specifying a Calculation Method for Duct Sizing

on page 182.

The calculations for duct friction losses are based on the Darcy and Altshul-Tsal equations described in the

2001 ASHRAE Fundamentals Handbook, Chapter 34, as follows:

■

Duct friction loss for round, rectangular, and oval ducts is calculated using equation 19.

■

Duct friction factor for round, rectangular, and oval ducts is calculated using equation 21.

■

Reynolds Number is calculated using equation 23.

■

Equivalent round duct diameter for a rectangular duct is calculated using equation 25.

■

Equivalent round duct diameter for a flat oval duct is calculated using equations 26, 27, and 28.

■

To size friction for the rectangular or oval duct, the calculations use the equivalent round duct diameter

and its velocity.

■

The dialogs for Add Ducts and Modify Duct list the actual velocity for the selected CFM and duct size,

not the velocity used in the duct friction calculations. The actual velocity is displayed for duct fitting

and acoustical analysis.

■

When a CFM is not displayed in the dialogs for Add Ducts or Modify Duct, the friction or velocity values

shown are the values specified in the Design Parameters for the Duct System Definition. To specify design

parameters for the Duct System Definition, see

Specifying a Calculation Method for Duct Sizing

on page

182.

The Add Ducts dialog shows an asterisk next to the Velocity field to

indicate that the constant velocity method was used to calculate duct size.

The Modify Duct dialog shows the fixed parameter value for velocity that was

used to calculate duct size.

Duct sizes are calculated based on the flow values assigned to all outlet devices detected in the system. For

more information on assigning flow values, see

Configuring Mechanical Parts for Analysis

on page 196.

170

| Chapter 6

Drawing HVAC Systems