100 Print Reading for HVACR
Copyright Goodheart-Willcox Co., Inc.
5.3.4 Transitions
In an air distribution system, it is often necessary to join two sections
of different-sized ductwork. A transition, Figure 5-26, is a duct fi tting
used to connect duct sections of different sizes. Most often, three sides of
the transition fi tting are parallel to the two sections being connected. In
some cases, especially when the duct system will be exposed, two or more
sides of the transition fi tting are angled, to provide a more symmetric
appearance.
Transition fi ttings can be either diverging or converging, Figure 5-27.
A converging transition is one that has air fl owing through it from the
larger size to the smaller size. A diverging transition is one that has air
fl owing through it from the smaller size to the larger size.
Different information can be pulled from a duct drawing based on
the type of view in the drawing. Figure 5-28 shows a plan view and an
elevation view of a duct run. Upon initial inspection of the plan view,
it appears to be a straight section of the same-sized ductwork. How-
ever, in reality, the actual duct run transitions from one size to another,
Boot Types and Applications
Type Symbol Application
4-V New construction projects
Round duct is left exposed within occupied
space
4-Z Ceiling applications
4-AA Ceiling applications
4-AO Wall applications
Used when occupied space on one side of
wall is supplied with air from particular duct
4-AP Wall applications
Used when both areas on side of wall is
supplied air from duct
Goodheart-Willcox Publisher
Figure 5-25 (continued ).
Goodheart-Willcox Publisher
Figure 5-26. A transition fi tting.
Converging
Diverging
Goodheart-Willcox Publisher
Figure 5-27. A transition fi tting is called
converging or diverging depending on
which side the air enters and travels
through fi rst.
Copyright Goodheart-Willcox Co., Inc.
5.3.4 Transitions
In an air distribution system, it is often necessary to join two sections
of different-sized ductwork. A transition, Figure 5-26, is a duct fi tting
used to connect duct sections of different sizes. Most often, three sides of
the transition fi tting are parallel to the two sections being connected. In
some cases, especially when the duct system will be exposed, two or more
sides of the transition fi tting are angled, to provide a more symmetric
appearance.
Transition fi ttings can be either diverging or converging, Figure 5-27.
A converging transition is one that has air fl owing through it from the
larger size to the smaller size. A diverging transition is one that has air
fl owing through it from the smaller size to the larger size.
Different information can be pulled from a duct drawing based on
the type of view in the drawing. Figure 5-28 shows a plan view and an
elevation view of a duct run. Upon initial inspection of the plan view,
it appears to be a straight section of the same-sized ductwork. How-
ever, in reality, the actual duct run transitions from one size to another,
Boot Types and Applications
Type Symbol Application
4-V New construction projects
Round duct is left exposed within occupied
space
4-Z Ceiling applications
4-AA Ceiling applications
4-AO Wall applications
Used when occupied space on one side of
wall is supplied with air from particular duct
4-AP Wall applications
Used when both areas on side of wall is
supplied air from duct
Goodheart-Willcox Publisher
Figure 5-25 (continued ).
Goodheart-Willcox Publisher
Figure 5-26. A transition fi tting.
Converging
Diverging
Goodheart-Willcox Publisher
Figure 5-27. A transition fi tting is called
converging or diverging depending on
which side the air enters and travels
through fi rst.