Dacor RV46 - Page 11

Calculating the Maximum Duct Run Length
• Do not use duct work that is smaller in cross-sectional
area than the required duct sizes in the table to the
right.
• For best performance, keep the duct run as short as
possible and never exceed the maximums stated at the
right.
The maximum straight duct length for the raised vent
system depends on the model of blower used with the
vent system and the number of elbows and transitions
used. The Equivalent Number of Feet for each elbow
and transition (see table) must be subtracted from the
maximum straight length to compensate for wind resis-
tance. To determine the maximum allowable length of
the duct work, subtract all of the equivalent lengths of
the elbows and transitions from the Blower Maximum
Duct Straight Length.
For example, for a raised vent system using 3 1/4" X
10" rectangular duct, two (2) 3 1/4" X 10" 90° elbows, a
3 1/4" X 10" rectangular to 10" round transition with a
REMP16 remote blower:
• From the Blower Maximum Duct Straight Length
table, the maximum length without transitions and
elbows is 60 feet.
• The equivalent length of each 90° elbow is 15 feet.
• The equivalent length of 45° elbow is 2 feet.
• The equivalent length of the transition is 4 feet.
• The total equivalent length of the above components is:
15 feet + 15 feet + 4 feet + 2 feet = 36 feet.
• The maximum amount of straight duct that can be used
with a REMP16 and the above components is: 60 feet -
34 feet = 24 feet.
Equivalent Number of Feet -
Duct Elbows and Transitions
45° elbow 3 ¼"X 10
3 feet 7 feet
8 Inch 45° elbow
45° elbow 3 %"X 10
2 feet 15 feet
10 Inch 90° elbow
90° elbow 3 ¼"X 10
7 feet 20 feet
8 Inch 90 ° flat elbow
3 %"X 10
90° elbow
5 feet to 8" round 4 feet
10 Inch
transition
90° 3 %"X 10 3 %"X 10
to 8" round 25 feet to 10" round 4 feet
transition transition
Roof cap* ** Wall cap with **
damper*
Not applicable for REMP series blowers.
** The equivalent lengths of roof and wall caps vary with
model and configuration. For equivalent length, contact the
manufacturer or a qualified HVAC specialist.
Blower Maximum Duct Straight Length
Blower
3 ¼" X 10"
Used 8 Inch Duct 10 Inch Duct
Duct
50 feet 40 feet 40 feet
CABP3
(15.2 meters) (12.2 meters) (12.2 meters)
60 feet 50 feet 50 feet
ILHSF8
(18.3 meters) (15.2 meters) (15.2 meters)
70 feet 80 feet 70 feet
ILHSF10
(21.3 meters) (24.4 meters) (21.3 meters)
60 feet 50 feet 50 feet
REMP3
(18.3 meters) (15.2 meters) (15.2 meters)
70 feet 80 feet 70 feet
REMP16
(21.3 meters) (24.4 meters) (21.3 meters)
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