Determining CFM (cfm)

After the model is known, the cfm must be determined. Consult local code requirements or the table below for suggested air changes for proper ventilation.

The ranges specified will adequately ventilate the corresponding areas in most cases. However, extreme conditions may require “Minutes per Change” outside of the specified range. To determine the actual number needed within a range, consider the geographic location and average duty level of the area. For hot

climates and heavier than normal area usage, select a lower number in the range to change the air more quickly. For moderate climates with lighter usages, select a higher number in the range.

To determine the cfm required to adequately ventilate an area, divide the room volume by the appropriate “Minutes per Change” value.

Suggested Air Changes for Proper Ventilation

 

cfm = Room Volume

Room Volume = L x W x H (of room)

 

 

 

Min./Chg.

 

 

 

Area

Min./Chg.

Area

Min./Chg.

Area

Min./Chg.

Assembly Hall

3-10

Dance Hall

3-7

Machine Shop

3-6

Attic

2-4

Dining Room

4-8

Mill

3-8

Auditorium

3-10

Dry Cleaner

2-5

Office

2-8

Bakery

2-3

Engine Room

1-3

Packing House

2-5

Bar

2-4

Factory

2-7

Projection Room

1-2

Barn

12-18

Foundry

1-5

Recreation Room

2-8

Boiler Room

1-3

Garage

2-10

Residence

2-6

Bowling Alley

3-7

Generator Room 2-5

Restaurant

5-10

Cafeteria

3-5

Gymnasium

3-8

Rest Room

5-7

Church

4-10

Kitchen

1-5

Store

3-7

Classroom

4-6

Laboratory

2-5

Transfer Room

1-5

Club Room

3-7

Laundry

2-4

Warehouse

3-10

Sample problem:

A building requires an exhaust fan to ventilate a general office (see diagram below) which measures 30 ft. x 40 ft. x 8 ft. The office is often crowded.

Solution:

The total room volume is 30 ft. x 40 ft. x 8 ft. = 9600 cubic feet. From the chart, the range for general offices is 2-8 minutes per change. Since the office has heavier than normal usage, 4 minutes per change is recommended. Therefore, the required exhaust is:

9600 ft3 = 2400 cfm

4 min.

Since the air to be exhausted is relatively clean, this is an ideal application for a model GB fan.

Note: In this example, make-up air was provided through a set of louvers at the wall farthest from the exhaust fan. If there were no provisions for make-up air in this room, a supply fan would also have to be sized. The supply cfm should equal the exhaust cfm. Supply fan location should be as far as possible from the exhaust fan.

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Greenheck Fan 240XP-CUb manual Determining CFM cfm, Suggested Air Changes for Proper Ventilation
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240XP-CUb specifications

The Greenheck Fan 240XP-CUb is a premium addition to the commercial and industrial ventilation market, delivering exceptional performance and reliability. Designed for a variety of applications, the 240XP-CUb combines cutting-edge technology with robust construction to ensure efficient airflow management.

One of the standout features of the 240XP-CUb is its energy efficiency. This model is engineered to minimize energy consumption while maximizing airflow, thanks to advanced motor technology and aerodynamically optimized fan blades. The fan operates with a sound level that is comfortably low, making it an ideal choice for environments where noise reduction is critical, such as schools, hospitals, and office buildings.

The 240XP-CUb is equipped with a high-efficiency, permanent split capacitor (PSC) motor that enhances its overall performance. This type of motor reduces energy costs while providing consistent operation, ensuring longevity and durability. With variable speed options, the fan can be tailored to suit specific application requirements, allowing for better control over airflow and energy use.

In terms of construction, the Greenheck Fan 240XP-CUb is built to last. It features a heavy-duty galvanized steel housing that is resistant to corrosion and can withstand the rigors of commercial use. This ensures that the fan remains reliable in various environments, from manufacturing facilities to food processing plants. The design also includes an easy-access panel for maintenance, further enhancing the unit's user-friendly nature.

Another significant aspect of the 240XP-CUb is its versatility. It can be installed in a range of configurations, including horizontal and vertical orientations, making it suitable for different spaces and applications. Furthermore, it supports a variety of accessories and options that allow for customization, such as inlet guards, dampers, and different mounting configurations.

The Greenheck Fan 240XP-CUb adheres to the latest regulatory standards for efficiency and emissions, making it an environmentally friendly choice for businesses looking to reduce their carbon footprint. With its combination of performance, efficiency, and durability, the 240XP-CUb stands out as a top-tier solution for anyone in need of reliable ventilation solutions. Whether for new installations or retrofits, this fan is designed to meet the demands of modern HVAC systems, ensuring a comfortable and healthy environment.
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