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Centrifugal Downblast Exhaust Fans
Suitable for general, clean air exhaust applications.
Direct drive, spun aluminum fans, designed for roof mounting on a curb for general, clean air exhaust applications.
Belt drive centrifugal roof exhaust fans, designed for clean air applications where the air discharge is downward, toward the roof surface.
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Performance Filter
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Calculate Air Exchange (CFM)
Use the calculator to determine the Air Exchange (CFM) required to adequately ventilate an area.Enter information into the fields below in order to calculate the CFM (per fan).
To calculate the CFM required to adequately ventilate an area, we divide the room volume by the appropriate "Minutes per Change" value.
[CFM] = [Room Volume] / [Min./Chg.]
Airflow (CFM) per Fan
*
Starred items represent required fields.
Calculate Static Pressure (SP)
Use the calculator to determine the amount of static pressure the fan must overcome.The pressure generated by fans in ductwork is typically very small. An accurate measurement of static presure is critical to proper fan selection however. Static pressure in fan systems is typically less than 2" SP, or 0.072 Psi.
The amount of static pressure that the fan must overcome depends on the air velocity in the ductwork, the number of duct turns (and other resistive elements), and the duct length. For properly designed systems with sufficient make-up air, the guidelines in the table below can be used for estimating static pressure.
Static pressure
* Starred items represent required fields.
Static Pressure Guidelines
Non-Ducted 0.05" to 0.20"
Ducted 0.20" to 0.40" per 100 feet of duct (assuming duct air velocity falls within 1,000 to 1,800 feet per minute)
Fittings 0.08" per fitting (elbow, register, grill, damper, louver, duct turn, etc.)
Kitchen Hood Exhaust 0.625" to 1.50"
Important: Static pressure requirements are significantly affected by the amount of make-up air supplied to an area. Insufficient make-up air will increase static pressure and reduce the amount of air that will be exhausted. Remember, for each cubic foot of air exhausted, one cubic foot of air must be supplied.
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Shop Greenheck Centrifugal Downblast Exhaust Fans
Roof mounted centrifugal downblast exhaust fans include direct- and belt-driven fans. These models have backward-inclined centrifugal wheels and are suitable for applications exhausting relatively clean air.Find by Performance
Our performance filter tool can help you choose the right product based on your performance requirements.
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Applications/uses for a particular fan or ventilator.
Refers to the location where a fan or ventilator can be mounted.
Square base dimension on power roof ventilators. Square fan panel dimension on sidewall propeller fans.
Transmission type of the ventilator (belt drive or direct drive).
Indicates the space relationships of windings and changing values of the recurring cycles of AC voltages and currents. The most common power supplies are either single- or three-phase.
The force that causes a current to flow in an electrical circuit. The voltage of a motor is usually determined by the supply to which it is attached. NEMA requires that motor be able to carry its rated horsepower at nameplate voltage plus or minus 1% al
The power required to drive an air moving device. Horsepower required varies with system conditions.
The "ACTUAL" damper width and height. Dampers are undersized to allow them to be mounted into the duct work/wall opening.
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Version 1.0, April 2019
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