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The following information serves as a guideline only. Ductwork should
be installed in accordance with local codes and restrictions. IT IS
THE RESPONSIBILITY OF THE INSTALLER TO CHECK LOCAL CODES BEFORE RUNNING
DUCT.
- All exhaust ductwork must be installed in the most direct manner possible.
- Exhaust duct must be made of 16 gauge steel or 18 gauge stainless steel.
- Per NFPA-96-Chapter 3, all exhaust duct seams and joints must have a
continuous liquid tight external weld.
- EXHUAST RISERS on the hood have been sized to achieve the velocity of
1500-2200 FPM (NFPA-96) based on the CFM required for the hood. Please be
sure to maintain the area of each riser when connecting duct, offsets
or transitions to it.
- Branches should enter at gradual expansions and at an angle of 30 degrees or
less (preferred) to 45 degrees if necessary. Avoid "T" intersections.
- When a "PANTLEG DUCT" is required to bring two ducts into one exhaust fan,
please observe the following:
- Use ONLY radius back and radius throat elbows. (2 to 2.5 diameter
center line radius is recommended)
- Maintain the distance between the center line of exhaust ducts
at a maximum of 12' apart.
- The main duct going to the exhaust fan must be the sum of the area
of the separate legs.
- MAKE-UP AIR RISERS are sized around 800-1200 FPM. Maintain this area when
installing ducts.
- DO NOT use "flexible" type duct for make-up air duct, as it has higher pressure losses
caused by the friction of the irregular inside duct surface. Only the rigid type
duct installed in accordance with SMACNA/HVAC Duct Construction Standards will
be acceptable.
- 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 make-up air duct by the installer.
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