Duct Run Calculation - Crown PRO-INS24N1 Instruction Manual

Ducting (not provided)
NEVER exhaust air or terminate
duct work into spaces between
walls, crawl spaces, ceiling,
attics or garages.
All exhaust must be ducted to
the outside.
Use Metal duct work only.
Fasten all connections with
sheet metal screws and tape all
joints with certified Silver Tape
or Duct Tape.

Duct Run Calculation:

Maximum run 6" or 3-1/4"
x 10" duct
Deduct:
Each 90 Elbow used
Each 45 Elbow used
Each 6" to 3-1/4" x 10"
transition used
Each 3-1/4" x 10" to 6"
transition used
Side Wall Cap w/ damper
Roof Cap
e.g. – 1 roof cap, 2x90 elbows,
1x45 elbow = 30" + 30" + 9"=69"
used, 31" available for straight
duct runs
DUCT SIZE
A minimum of 6" round duct must be used
to maintain maximum airflow efficiency.
Flexible ducts are provided for convenience,
100FT
always use rigid type metal ducts if available
to maximizing airflow.
Also use calculation (on left) to compute
15FT
total available duct run when using elbows,
15FT
transitions and caps.
1FT
ALWAYS, when possible, reduce the
number or transitions and turns. If a long
5FT
duct required, increase duct size from
6" to 7 or 8".
30FT
If a reducer is used, install a long reducer
30FT
instead of pancake reducer. Reduce duct
size as far away from opening as possible.
If turns or transitions are required:
Install as far away from opening and
as far apart, between 2, as possible.
5