92 Print Reading for HVACR
Copyright Goodheart-Willcox Co., Inc.
Supply ducts and return ducts can be distinguished from each other
by the lines within the symbol, Figure 5-8. Supply ductwork is often
indicated by an X marking in the section, while return ductwork is
often identifi ed by a single diagonal line. Drawings may also indicate
the cross-sectional dimensions of the duct preceded by an S for supply
or an R for return. Systems with exhaust ducts use a symbol that is a
cross between the supply duct and return duct symbols, and are often
identifi ed by the letter E.
Although air enters an air distribution system at the return grille,
moves to the air handler, and then to the conditioned space, it is often
diffi cult to identify the direction of airfl ow through these components in
a print. The direction of airfl ow through a duct is usually indicated on
plans using arrows, Figure 5-9. A straight-shafted arrow indicates the
direction of supply airfl ow, while an arrow with a break mark on the
shaft indicates the direction of return airfl ow.
Dashed lines and parentheses are commonly used on duct section
drawings to represent hidden objects, Figure 5-10. When a duct is fabri-
cated with acoustical lining for sound dampening, dashed lines are drawn
within the duct drawing. When a duct run, or a portion of it, is hidden
from view, the duct section is drawn with dashed lines and the duct’s
dimensions are drawn in parentheses.
5.3 Fittings
Fittings are sections of ductwork used to change the direction or size
of a duct run. They can also be used to split an airstream into two or
more airstreams or connect a duct to another air-side system compo-
nent. A number and letter combination used to label the fi tting is the
construction number. Each fi tting has a distinct construction number.
5.3.1 Supply Air Fittings
Depending on the system confi guration, the primary supply trunk may
extend in a direction that is in-line with the direction of the discharge air-
stream from the air handler, Figure 5-11. Other times, the primary supply
trunk needs to be redirected using fi ttings. Most often, this is due to space
constraints, obstructions, or other design considerations. One of the most
commonly used methods of redirecting the primary supply airstream is to
connect a straight section of ductwork to the supply plenum, Figure 5-12.
Break mark
Return
Supply
Goodheart-Willcox Publisher
Figure 5-9. The direction of airfl ow
through supply and return ducts.
14 × 10
(14 × 10)
A
B
Goodheart-Willcox Publisher
Figure 5-10. A—Dashed lines indicate
that the duct section has acoustical
lining. B—Dashed lines indicate that the
duct section is hidden. Hidden ducts
also have their measurements shown in
parentheses.
Return Exhaust
R 20 × 14
Supply
S 24 × 14 E 20 × 14
Goodheart-Willcox Publisher
Figure 5-8. Representations of various duct systems.
Copyright Goodheart-Willcox Co., Inc.
Supply ducts and return ducts can be distinguished from each other
by the lines within the symbol, Figure 5-8. Supply ductwork is often
indicated by an X marking in the section, while return ductwork is
often identifi ed by a single diagonal line. Drawings may also indicate
the cross-sectional dimensions of the duct preceded by an S for supply
or an R for return. Systems with exhaust ducts use a symbol that is a
cross between the supply duct and return duct symbols, and are often
identifi ed by the letter E.
Although air enters an air distribution system at the return grille,
moves to the air handler, and then to the conditioned space, it is often
diffi cult to identify the direction of airfl ow through these components in
a print. The direction of airfl ow through a duct is usually indicated on
plans using arrows, Figure 5-9. A straight-shafted arrow indicates the
direction of supply airfl ow, while an arrow with a break mark on the
shaft indicates the direction of return airfl ow.
Dashed lines and parentheses are commonly used on duct section
drawings to represent hidden objects, Figure 5-10. When a duct is fabri-
cated with acoustical lining for sound dampening, dashed lines are drawn
within the duct drawing. When a duct run, or a portion of it, is hidden
from view, the duct section is drawn with dashed lines and the duct’s
dimensions are drawn in parentheses.
5.3 Fittings
Fittings are sections of ductwork used to change the direction or size
of a duct run. They can also be used to split an airstream into two or
more airstreams or connect a duct to another air-side system compo-
nent. A number and letter combination used to label the fi tting is the
construction number. Each fi tting has a distinct construction number.
5.3.1 Supply Air Fittings
Depending on the system confi guration, the primary supply trunk may
extend in a direction that is in-line with the direction of the discharge air-
stream from the air handler, Figure 5-11. Other times, the primary supply
trunk needs to be redirected using fi ttings. Most often, this is due to space
constraints, obstructions, or other design considerations. One of the most
commonly used methods of redirecting the primary supply airstream is to
connect a straight section of ductwork to the supply plenum, Figure 5-12.
Break mark
Return
Supply
Goodheart-Willcox Publisher
Figure 5-9. The direction of airfl ow
through supply and return ducts.
14 × 10
(14 × 10)
A
B
Goodheart-Willcox Publisher
Figure 5-10. A—Dashed lines indicate
that the duct section has acoustical
lining. B—Dashed lines indicate that the
duct section is hidden. Hidden ducts
also have their measurements shown in
parentheses.
Return Exhaust
R 20 × 14
Supply
S 24 × 14 E 20 × 14
Goodheart-Willcox Publisher
Figure 5-8. Representations of various duct systems.