Horsepower or CFM?

[Jim Becker]

WIthout a fan curve...something difficult or impossible to obtain for mass market dust collectors...you're going to have to just try and do the best you can....higher horsepower/larger blower size (both required) is going to move more air, regardless of the actual potential CFM, than something with a smaller motor/impeller. Dust collection is all about air flow...the more air you move, the better the dust collection performance. Beyond that, most bag systems have bag filters that are not the best...you will very often be better service by immediately replacing them with something from a company like American Fabric Filter or similar.

[Bill Dufour]

Makers lie about horsepower and airflow all the time. I think the best idea is to compare amps. Most motors are similar efficiency so more amps means more power. If you have fan curves that will mean something if it is a honest maker. If the curve is from a unknown Harbor freight unit I would not believe the paper it is written on.
Bill D

[Curt Harms]

As others have said, horsepower is, in my opinion, about worthless as a measure of dust collector capacity. CFM is better but in most cases that is the absolutely best performance the system is capable of - probably no hoses, no filters or any other performance robbing necessities when measured. The other number I would look at would be blower diameter. If two blower wheels are of the same design, a larger diameter blower will move more air regardless of the motor turning it. A 10" blower with a 10 hp motor turning it will move less air than a 12" blower with a 2 hp motor turning it. This assumes the same RPM in both cases.

[Jim Becker]

I'm with Curt...hp and amps are not deciding factors...the impeller is where the chips meet the road. But obviously, a motor capable of spinning that impeller is important.

[james manutes]

I'm on my third shop built cyclone , only because I'm a "horse trader" . But one other thing to mention is the weight of your impeller if you change it . Newer ones could be cast aluminum , potentially lighter than steel , it varies . I would avoid putting a much heavier impeller on a 1.5 HP unit , compared to what came off it . 2 - 3 HP will be less risky , I'd say . My last build I upgraded from a small steel of 7.75 lbs. to a larger aluminum impeller a little less than 9 lbs . I was a little worried that may be too heavy , but its been fine . The DC I used was a 2HP Grizzly , no issues going on 3 years of almost daily use .

[roger wiegand]

I don't understand why CFM is not the right measure. Of course I would not believe the manufacturers claims (nor are they particularly relevant, vs all the variables in an installed system), but it doesn't seem as though it would be difficult to use an anemometer to measure fpm through the collector in the first place (if you know that and the duct size cfm is an easy calculation) and then see how it is affected by variables like different layouts and pipe types.

I use a much cruder measure myself, that is do the chips get picked up and dropped in the collector bin without clogging. I've reconfigured a couple times to make that happen as new machines are added or moved around.

[Jim Becker]

I don't understand why CFM is not the right measure.

It actually is the right measure. The problem is determining what it actually is for a given system because mass-market folks tend to publish misleading information and don't provide fan curves. So about the best way for someone to "generally" determine what a system can do is to look at impeller size. The majority of folks don't have measuring devices to determine air flow and even if they do, it means actually buying the system first so you can test it. It's kinda a shame that the industry is the way it is where you can only get "real information" from a few specialty manufacturers that can be trusted...because they do provide fan curves.

[Larry Frank]

CFM is a good measure but as mentioned difficult to get properly. Fan type anemometers are not a good way to measure and lead to wildly inaccurate results.