(12-14-2016, 10:09 PM)Arlin Eastman Wrote: We need two tools very much
One is a dust collector and want to know if this one will work.  Both of them are less they $650

http://www.maxtool.com/shop-fox-w1687-3-h-p-2-800-cfm-dust-collector-w-2-800-cfm-air-suction-capacity?gclid=Cj0KEQiA-MPCBRCZ0q23tPGm6_8BEiQAgw_bAjDqWbDQEw0AS_uOWsUiKt8jMn91UZSZnXjgVdUf0zMaAg5R8P8HAQ

The above is 3hp with a 13.5" impeller in it, OR this one

The '3 hp' figure looks a little iffy, but the impeller is consistent with a 3 hp unit.  It claims 12A at 240V, but without a run capacitor (only has one hump), it's not likely.  Static pressure (full stall, I presume) is typical, though you don't operate at or near zero air flow, so that figure is kind of useless.  What you really need is the flow vs SP curve, which most small DC manufacturers don't like to publish.

https://www.amazon.com/Oasis-Machinery-DC5000-Heavy-Collector/dp/B005LO9WMW/ref=sr_1_fkmr0_1?s=hi&ie=UTF8&qid=1481760074&sr=1-1-fkmr0&keywords=SHOP+FOX+W1687+3-Horsepower+2%2C800+CFM+Dust+Collector

This one has a 5hp 12" smaller.

This one looks like HF-style wishful thinking.  12A at 220V is 5.3 hp before taking into account efficiency (80% or less) and power factor (also 80% or less, unless it has a run capacitor, which it does not, at least in the picture), which would work out to 3.3 hp, or somewhere around there.  Probably a 3 hp motor.  And a small impeller, especially for '5 hp'.  

I am thinking it is not the HP but the size of the impeller which creates the best suction.

You're thinking is on the right track.  All other things being equal, increased diameter will increase the static pressure, and generally have a higher flow vs SP curve, and therefore move more air, and take more input power to do it.  Other things can influence it, strongly sometimes, like impeller vane shape (airfoil is much more efficient, for instance), but as a general rule, high hp units have larger diameter and deeper impellers with higher max SP.  High pressure blowers, for instance, can have thin impellers, but very large diameter.  Like a typical vacuum cleaner, or big industrial blowers designed for low flow at high SP. 

DC's are designed to move a lot of air at a medium SP, so they're narrower and larger dia. than a squirrel cage HVAC blower, but not as narrow and much deeper than a high suction 'vacuum', or high pressure blower.  With few vanes, so allow debris to pass without clogging.

I am thinking for the price both would be a great machine's for us.

I agree with the other posters about the 30 micron bags.  That's a non-starter for me.  There are other DC units with filters or 1 micron bags.  And do use a pre-seperator of some kind.  Emptying bags is a drag.

Any and all advice is most welcome on this.