Sound Levels
In many cases, the sound generated by a fan must be considered. For the fan industry, a common unit for expressing sound pressure level is the sone. In practical terms, the loudness of one sone is equivalent to the sound of a quiet refrigerator heard from five feet away in an acoustically average room.
Sones are a linear measurement of sound pressure levels. For example, a sound level of 10 sones is twice as loud as 5 sones.
Refer to the Suggested Limits for Room Loudness chart to determine the acceptable sone range for the application. As a general guideline, choose a fan that has a sone value within the range specified.
Note: Rooms with a hard construction (concrete block, tile floors, etc.) reflect sound. For these rooms, select fans on the lower end of the range. Rooms with soft construction or those with carpeting and drapes, etc., absorb sound. For these rooms, fans near the higher end of the range may be selected.
Our example describes an exhaust fan for an office. Referring to the “Suggested limits for Room Loudness” chart, offices should have a loudness range from 4 to 12 sones. Of our remaining three selections, only the
Suggested Limits for Room Loudness
Sones | DBA |
|
Private homes (rural and suburban) | ||
Conference rooms | ||
Hotel rooms, libraries, | ||
|
| movie theatres, executive offices |
Schools and classrooms, | ||
|
| hospital wards, and operating rooms |
Court rooms, museums, | ||
|
| apartments, private homes urban) |
Restaurants, lobbies, | ||
|
| general open offices, banks |
Corridors and halls, cocktail lounges, | ||
|
| washrooms and toilets |
Hotel kitchens and | ||
|
| laundries, supermarkets |
Light machinery, assembly lines | ||
Machine shops | ||
Heavy machinery |
From AMCA Publication 302 (Application of Sone Ratings for Non Ducted Air Moving Devices with
Motor Horsepower
The motor horsepower for direct drive fans is always sized by Greenheck and does not require further consideration. For belt drive models, the catalog identifies which horsepower is recommended. However, there are times when it is wise to bump the horsepower one size. For example, the hp recommended for the
Although a 1/3 hp motor is recommended, it is not necessarily a good motor selection for this application. Our static pressure of 0.5 in. was only an estimate. It may actually turn out to be .625 in.
If this is the case, we will need a 1/2 hp motor because our fan will have to run at almost 900 rpm (refer to performance box - 2624 cfm at 0.625 in.Ps). Therefore, choosing a 1/2 hp motor in this case is exercising good judgement.
The complete model designation for this application is
Note: The
(refer to model column in catalog). This means that if the static pressure is less than estimated, say 0.25 in. Ps, the fan can be slowed down to accommodate this condition.
19
