Introduction to FAN SELECTION

Determining 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

Restroom

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.

Exhaust fan to be sized

30 ft.

Louvers to supply

Makeup air

8 ft.

40 ft.

F A N F U N D A M E N T A L S

131

 

 

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Greenheck Fan 129 manual Determining CFM, Sample problem, Area Min./Chg

129 specifications

Greenheck Fan 129 is a notable addition to the HVAC industry, recognized for its advanced technology and efficient performance. Designed primarily for ventilation, exhaust, and supply applications, the Greenheck Fan 129 excels in various commercial and industrial settings.

One of its key features is its robust construction. The fan casing is made of high-quality, corrosion-resistant materials, ensuring long-term reliability even in challenging environments. This durability is complemented by precision-engineered components, such as the impeller, which is constructed with advanced aerodynamics to optimize airflow and reduce noise levels. This focus on sound performance is particularly important in settings like schools and hospitals where acoustics are crucial.

The Greenheck Fan 129 also stands out due to its energy efficiency. It employs high-efficiency motors that meet or exceed the latest EPA and ASHRAE guidelines. This feature not only reduces operational costs but also supports sustainability efforts in organizations aiming to minimize their environmental footprint. With variable speed drive options, users can further enhance energy savings by matching fan speeds to the specific requirements of their application.

Safety and ease of maintenance are other significant considerations in the design of the Greenheck Fan 129. The fan includes access points that simplify inspections and repairs, reducing downtime and maintenance costs. Automated monitoring systems can also be integrated, providing real-time feedback on fan performance and system health to ensure that it operates at peak efficiency.

Moreover, the Greenheck Fan 129 is versatile in installation options. It can be mounted in various configurations, making it suitable for roof-mounted, wall-mounted, or inline applications. This adaptability makes it a favorite among engineers and contractors looking for reliable and flexible solutions for HVAC systems.

In summary, the Greenheck Fan 129 represents a blend of high performance, energy efficiency, and ease of use. Its durable construction, advanced aerodynamics, and safety features make it an ideal choice for a wide range of ventilation requirements. Whether for commercial buildings or industrial facilities, the Greenheck Fan 129 stands out as a top-of-the-line option for reliable and efficient airflow management.