News Industry News Tips for Choosing CFMAir Flow
Tips for Choosing CFMAir Flow
TIME:2014/3/23 12:47:38
Cubic Feet per Minute (cfm) is a measure of the volume of air being exhausted through your range hood. This measurement is always based on when the hood is running at full speed and at zero pressure, i.e. without the resistance of any ducting. Depending on its distance to the outside, the type and number of bends, and the resistance of the blow-back damper and wall plate, this output may be considerably reduced. There are 100-300 CFM/300-600CFM/600-900 CFM/900-1200CFM/1200CFM and up.

The cfm requirement for your kitchen therefore will depend on the type and output of your range top, the size of the hood, the positioning of the hood, plus the length and configuration of your ductwork. Every situation is different so I can only make average suggestions for the cfm required; but I can say with confidence that it is better to have too much than not enough.

Suggested CFM requirements for Cooktops:
Generally speaking an electric cook top is low powered and should only need a range hood output between 150cfm - 300cfm. If you have an electric deep fat fryer you will need to treat it as if it was a gas stove top.
"Regular" gas cook tops have outputs of up to around 40,000btu [British Thermal Units] and, since they are almost always used in an "against the wall" situation, you can use this simple formula to help make your choice. Calculate your cook top's btu rating by adding the power of each burner and then divide the total by 100, e.g. a 30,000btu top will require a 300cfm fan.
High Output ["Professional"]:
Professional style range tops can reach outputs akin to a small stove in a restaurant and they can generate enormous amounts of heat. The simple calculation of Total BTUs/100 = CFM (e.g. a 60,000 BTU top will need 600cfm blower) is fine in many situations, but you may need to consider more CFM:
if you have an extra long run of ducting (especially with 90degree bends).
if the range hood is positioned extra high over the range top;
if you cannot provide a bigger catchment area by choosing a width and depth greater that the range top - especially in an island or peninsula situation;
if you want to keep the noise level down by choosing an extra powerful hood but running it at a lower setting.
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