| Electrical & Lighting Expert
Join Date: Jan 2005
Posts: 4,555
| The proper method of choosing a fan is based on the amount of air that should be changed in an hour.
Once the proper size fan is chosen, then electrical calculations would then be considered.
A popular brand of various fans is Nutone.
The following link is to their Fan Catalog, on page 44 begins the complete specs for bath fans.
http://www.nutone.com/PDF/catalogs/NuFans-10_05.pdf[/url]
As you can see the amp draw varies as to the CFM, Cubic Feet per Minute, the rating of the amount of air the fan can move. This is the important value that needs to be calculated to size a fan for the room it will serve. Certain rooms, as suggested by The Home Ventilating Institute, need to have the air changes so many times per hour, which will produce a constant to calculate the CFM.
By using the information on Page 7, a sample bathroom with 8 ft high ceiling and is 10ft x 8ft floor space is calculated by:
8x8x10 x .13= 83.2 minimum CFM recommended for this room.
You will find one 50 CFM drawing .75 amps,and another 50 CFM drawing .15 Amps. The reason that two 50 CFM fans draw different amps is due to other factors, one being Sones, a measurement of noise, or how quiet the fan will operate, and if the fan motor is energy efficient.
Other fans listed:
70 CFM 1.2 amps
80 CFM .75 amps
90 CFM .5 amps
100 CFM .22 amps
110 CFM .85 amps
And many others, several with the same CFM and different amp draw.
As you can see there is many fans, I suppose without counting and calculating, a 1 Amp draw is a good compromise for an average.
You ask for wattage, wattage is calculated by multiplying voltage x amps, 120 x 1= 120 watts.
I wonder how many people, knowing that they need a fan in a certain room, but want to spend the least amount of money, stick a 50 CFM fan that costs $20, instead of buying the proper size fan , say a 100 CFM that costs $80. They saved $60, and then, two years later they spend $200.00, CHEERFULLY, to paint/wallpaper the bathroom again, all because the original fan they got was too small. Oh by the way, notice they did not install the correct size fan during this remodel, and they will paint/wallpaper again in a couple of years, and then need to live with poor ventilation, paint peeling, mold growing, etc.
Contractors that build subdivisions ,5,10,50,200 homes are real good at using the wrong size fan. They can save huge amounts of money, and a few years later, the owners need to deal with the damage and inconvenience of the wrong fan.
I bet you did not expect this much information for your simple question. Since many people review these answers, I took this opportunity to help educate those who may benefit from this information.
I hope I have answered your question, if not please get back with your questions. |
Linear Mode
