# Something you don't see too often on dust collector specs...



## Marv (Nov 30, 2008)

Delta is actually listing the unrestricted and restricted CFM numbers of their new portable cyclone dust collector. 

http://www.deltamachinery.com/products/dust-management/item/50-905?category_id=3

Unfortunately they don't list what the "restrictions" are but I'm thinking if all manufacturers showed a restricted number in conjunction with a certain length of a certain size pipe it would at least make it a bit easier for people to compare/decide what will work best for their situation. Then all we would need is for shop vacuum manufacturers to quit posting those ridiculous "peak" HP ratings  and list some "real" specs people could actually use to compare.


----------



## Leo G (Oct 16, 2006)

The unrestricted number is worthless unless you plan on buying a $1200 fan. I would hope the the restricted number is when it was all assembled with the filter in place. I doubt it has anything hooked up to it like ducting.


----------



## Marv (Nov 30, 2008)

Leo G said:


> The unrestricted number is worthless unless you plan on buying a $1200 fan. I would hope the the restricted number is when it was all assembled with the filter in place. I doubt it has anything hooked up to it like ducting.


 That's exactly the problem I see with the way most dust collector specs are listed..they typically show the "worthless" unrestricted number yet all the dust collector sizing charts I've seen online help you arrive at somewhat "real world" numbers needed based on your specific machinery requirements/ducting losses etc. This could and I'm sure has caused some to under-power their dust collection systems since they were comparing a "real world" number with a worthless one (unless they planned to hook the fan directly to the machine with no filter  and even though my "hope" as well is the restricted number in this case meant with the cyclone and filter attached, I still don't know for sure because they didn't specifically state that). In any case the numbers will be very different from the fan inlet to the cyclone inlet with or without the filter and I think it would make things easier if the specs said _something like "actual CFM/SP at the hose inlet with the filter attached"_. 

BTW, one of the reasons I bought the Cincinnati Fan collector I have is because the specs specifically stated _"CFM/SP with a 5" x 5' long hose connected and filter attached"._


----------



## Leo G (Oct 16, 2006)

Gotta look for a machine that shows the fan curve. Oneida does this.


----------



## mveach (Jul 3, 2010)

Some manufactures will state cfm @ sp. This will you everything you need.


----------



## WillemJM (Aug 18, 2011)

Restricted probably should mean with the cyclone, bag and filter in place.

810 CFM is a bit ambitious for a 1 1/2 hp fan.

Once piped up in a standard configuration, think it will be closer to around 550 CFM


----------



## TimPa (Jan 27, 2010)

mveach said:


> Some manufactures will state cfm @ sp. This will you everything you need.


i agree. a cfm number is useless without a static pressure. the 2 numbers are interdependent. it's similar to saying my air compressor can produce 10 cfm - yes, but at what pressure, 150 psi? doubt it.


----------



## BigJoe16 (Feb 20, 2012)

The way i think of it is if every company gives you the same specs, wether there restricted or not, they are comparable. They might not be what your acutally going to get but you have an idea of one machine against another one. I agree that they should guve you the real numbers but they want to trick you so they never will.


----------



## Leo G (Oct 16, 2006)

There are some companies who will outright lie on their specs to make the sale. I have seen 3HP bag collectors claim 3000 CFM with a 12" impeller. Not happening. You need to be able to compare them and if they are based on the same observations then you can compare. If one collector claims 1000 CFM free air and another claims 850CFM at 2.5 SP, which is the better collector. You don't know. If you put 2.5 SP on that 1st collector it might drop down to 500 CFM.


----------



## Marv (Nov 30, 2008)

I "play" with mobile audio as well and find that many amplifier manufacturers do the same thing by showing "peak" power numbers but no mention of how they arrived at that number (I've seen amps advertised at "1000 watts peak power" yet they will have a 20 amp fuse on it! ) The "better" manufacturers will show "real" power ratings at a certain voltage (or different voltages ie 12.5v or 13.8v) which make those amps easier to compare power wise (there is also a CEA rating standard implemented a while back however not all amps adhere to it)


----------



## Leo G (Oct 16, 2006)

Yes, Peak vs RMS. Dealt with that for years. 

Ever look at shop vacs? 5HP yet it plugs into a 15 amp 120vac circuit. Not happening. You can get about 2 HP max out of a 15 amp outlet, and even that is pushing it because it will trip the breaker trying to start it.


----------

