FloAire Canopy Hood - Manual (Page 15)

15
Guidelines for Ductwork Installation
Ductwork is furnished by supplier only if specified by the customer. The following information is provided
as a guideline only. Ductwork should be installed in accordance with the local codes and restrictions. It
is the responsibility of the installer to check local codes prior to installing the ductwork.
1. All ductwork must be installed in the most direct manner possible.
2. Exhaust duct must be made of 16 gauge carbon steel, 18 gauge stainless steel or must be listed
for use with commercial kitchen hoods and follow the manufacturer’s listing.
3. Per NFPA 96, all exhaust duct seams and joints must have a continuous liquid tight external
weld; exception would be Listed Factory Built Grease Duct.
4. Exhaust risers on the hood have been sized to achieve a velocity of 500-2200 FPM, per NFPA
96, based upon the CFM required for the hood. Maintain the area of each riser when connecting
duct offsets or transitions.
5. Branches should enter at gradual expansions and at a preferred angle of 30 degrees or 45
degrees if necessary.
6. When a “pantleg duct” is required to bring two ducts into one exhaust fan, observe the following in
order to obtain desired performance:
a. Use ONLY radius back and radius throat elbows. 2 to 2.5 diameter center line radius is
recommended.
b. Maintain the distance between the center lines of exhaust ducts at a maximum of 12’
apart.
c. The main duct going to the exhaust fan must be the sum of the area of the separate legs.
7. Supply air risers are sized around a maximum of 600 FPM. Maintain this area when installing
ducts.
8. Do not use “flexible” type duct for supply duct. Only rigid type duct installed in accordance with
SMACNA Low Pressure requirements will be acceptable.
9. Access Doors should be provided at the sides or at the top of the duct, as well as changes of
direction. Please refer to your AHJ if questions on requirements for horizontal and vertical duct
run.
10. IMPORTANT: When a fusible link is installed in the make-up air damper at the hood collar, an
access door must be cut into the supply duct by the installer.
11. Duct sensor may ship loose on hoods with field cut risers. When double wall duct or ductwork
with a diameter smaller than 10” is used, loose duct sensors should be installed in the top of the
plenum near the riser in the path of the exhaust airflow.