Product Overview
5
Dryers operate most efficiently when exhaust
velocities between 1200-2200 feet-per-minute
(FPM) are maintained. The number of co-ducted
dryers operating, exhaust fan model selection
and the diameter and length of the common
exhaust duct can dramatically affect exhaust
velocity. Follow the recommendations below to
maximize the efficiency of the Tjernlund exhaust
system and connected dryers.
Total
Dryer CFM
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
Common
Manifold
Minimum
Duct Dia.
6”
7”
8”
8”
9”
9”
10”
10”
10”
10”
12”
12”
Common
Manifold
Maximum
Duct Dia.
8”
9”
10”
10”
10”
12”
12”
12”
14”
14”
14”
14”
Rooftop
Mount
Series
RT750
RT750
RT750
RT750
RT1500
RT1500
RT1500
RT1500
RT1500
RT1500
RT1500
RT1500
Max.
Equivalent
Feet @
Min. Duct
Diameter
50
50
50
NA
150
50
100
75
50
50
75
50
Max
Equivalent
Feet @
Max. Duct
Diameter
200
150
150
50
200
200
200
200
200
200
150
150
Indoor
Mount
CDB8
CDB8
CDB8
CDB8
CDB8
CDB8
CDB8
CDB8
CDB8
NA
NA
NA
NA
Max
Equivalent
Feet @ Min.
Duct
Diameter
120
160
165
100
100
30
15
NA
NA
NA
NA
NA
Max
Equivalent
Feet @ Max.
Duct
Diameter
200
200
200
200
150
125
30
NA
NA
NA
NA
NA
Commercial Dryer Booster Selection and Duct Sizing Table
Selecting the proper commercial Dryer Duct Booster duct size
Important Common Manifold Construction Recommendations
Always install a capped length of straight pipe at least 1 pipe diameter long behind the dryer farthest
from the exhaust termination for a stable place to measure exhaust pressure.
Always connect individual dryers to the common manifold using wye connectors pointed towards the
exhaust termination. Do not use straight tee connections.
Over sizing the exhaust manifold will reduce
velocities and allow more opportunity for lint to
drop out of the exhaust stream. Undersized or ex-
cessively long exhaust manifolds will increase drying
time and operating costs. COP controller set point
adjustments will allow velocities to be fine tuned.
Contact Tjernlund Tech Service for advice on applications outside the boundries of this table.
1. Based on the CFM total for all connected
dryers find the Total Dryer CFM value in the left
column of the table equal to or greater than
that CFM and determine the common manifold
minimum or maximum duct diameter.
2. Trace to the right to select the Dryer Booster
and determine the maximum equivalent length
of common duct based upon your choice of ei-
ther the minimum or maximum duct diameter.
Example: 4 Dryers @ 225 CFM/ea.
4 x 225 = 900 Total Dryer CFM
Minimum duct diameter at 900 CFM is 9 inches
Maximum duct diameter at 900 CFM is 12 inches
Installing a common duct sized between 9” and 12”
is the optimal size range for maintaining a proper
velocity across all operating conditions. Trace to the
right to select the Dryer Booster and maximum
equivalent feet of common duct based on your
duct diameter choice.
Common exhaust manifold sizing and Dryer Booster Fan selection