Fan curve for 3HP DC?

[Lou Stags]

I am investigating purchasing a 3HP DC (not a cyclone). I am struggling to find a fan curve for 3HP'ish "traditional" DCs. For example, here is a unit from Grizzly I wish they had specs for:

http://www.grizzly.com/products/3-HP-Dust-Collector-with-Aluminum-Impeller-Polar-Bear-Series/G1030Z2P

I would like to maintain at least 700 CFMs at 11" SP. Anyone have info on where I can find a machine similar to the one linked above that has a fan curve? I am hoping to buy a cheaper DC, swap it out with Wynn filters, and build a Thien baffle. If I can't find something that meets my CFM requirements, I will just bite the bullet and get the 3.5 Tempest Cyclone from Penn State Industries... But I would rather save some cash and put that towards the ductwork.

Any suggestions?

[Ole Anderson]

Here is one from Oneida for the 3 hp Super Dust Gorilla, (applies if you bite the bullet):

http://www.oneida-air.com/Images/Static/3hp-super-curve.jpg

[David Kumm]

DC curves are notorious for not being real reliable but the Cincinnati fan curves show a 14" BC impeller will deliver over 700 cfm at 11". Their design may be a little more efficient but generally you are in the right size range. Not using a cyclone saves 2-5" so that helps. If you use bags, get good ones and oversize them as much as possible. I'm not a cartridge guy for a straight bagger but the Wynn are probably a good bet since they are very tight pleat so chips have a harder time getting caught. Chips are not good for a cartridge so you want one that allows them to fall off. If Wynn says they are good for that I'll defer to him. If you were collecting dust I'd stay with good bags. Either way keep them clean as the cfm drops quickly on the smaller DC impellers when the SP increases. Dave

[ian maybury]

+1 on the Cincinatti Fan curves (actually tables) being a pretty good and more to the point reliable source for impeller performance data. Go to their website, look of the listing of fan models and click a representative one. (the SPB model is a pretty close to the sort of impeller used routinely on dust systems - choose a BC type though, and go for the table that matches your RPM): http://www.cincinnatifan.com/select.htm

The tables list CFM vs. pressure drop - they in effect are fan curves...

A 3HP fan if it's truly that and uses a typical BC radial impeller should comfortably do the required CFM - provided that is the hoses/ducts are kept short (as in a small shop) and the machine hoods are not restrictive. (don't expect to hang 50 ft duct runs out of it, or run tightly hooded machines and get that) It's possible to extract pressure drop info for your ducting runs using either Bill Pentz's calaculator, or estimating from the information in the Engineering Data manual linked from the same CF page. (but don't forget to add pressure drop for filters, cyclone etc if applicable)

ian

[Lou Stags]

Based on this article:
http://www.portercable.com/uploads/PCD/Documents/News/182DustCollectors.pdf

It looks like Grizzly's 2 HP unit with 6" ducts will perform decently. A few questions:

1. How much better do you think their 3 HP unit will perform compared to the 2HP one in the article above(the 3HP unit is the one I linked to in the first post of this thread)?
2. Do I "have" to use the double bag setup on the 3HP unit? I would be interested in only using 1 bag to save some space (I also plan on building a Thein baffle for this setup). Looking at the pics, looks like I may be able to unbolt the motor from the connector piece, and bolt it directly to one of the bags. This approach would also save me from needing to buy 2 Winn filters.

Thoughts? Help a newbie out! :)

[david brum]

1. How much better do you think their 3 HP unit will perform compared to the 2HP one in the article above(the 3HP unit is the one I linked to in the first post of this thread)?

These are essentially the same DC, except the 3 hp unit has twice as much filter area. One of the big restrictions with dust collectors is how much air they can exhaust. If you can exhaust twice as much air through the filters, you can move a lot more air with your DC. Twice as much surface area implies twice as much air flow. I'm sure it isn't that simple, but you get the idea.

The larger airflow also makes the motor work harder. The larger motor on the 3 hp DC is required to handle the extra work.



2. Do I "have" to use the double bag setup on the 3HP unit? I would be interested in only using 1 bag to save some space (I also plan on building a Thein baffle for this setup). Looking at the pics, looks like I may be able to unbolt the motor from the connector piece, and bolt it directly to one of the bags. This approach would also save me from needing to buy 2 Winn filters.


If you only use one set of bags on the 3 hp unit, you'll cut the filter area in half, effectively converting it to the same capacity as the 2 hp unit. You'll move less air and have unused motor capacity. It will look cool, though.

To further confuse issues, I have personally used a 3 hp DC with Wynn filters and Thien baffles. It didn't really work as well as I'd hoped. My previous experience was with a Jet 1.5 hp DC with Wynn filter and Thien separator. It worked great and i rarely had to clean the filter. The 3 HP units just move too much air for a Thien filter to work, however. Thien separators (brilliant inventions and thanks to Phil for sharing these with us) work by slowing the air enough for the fine dust to fall out. As the air flow increases, I don't think it can slow enough for this to take place. That was my experience, anyway. I had high hopes, but found myself constantly cleaning the filters. I guess I could have decreased the airflow to make it work better, but that defeats the purpose.

Having said all of that, a 2 hp DC with Wynn filter and Thien separator should work fine for you. What would work even better would be a 3 hp DC, vented outside. Since you live in a pretty temperate climate, you could easily pull this off as long as your next door neighbors aren't too close. That would give you an inexpensive DC with stellar performance and no filters to clean. I decided to vent outside a few years ago and have zero regrets.

[Lou Stags]

These are essentially the same DC, except the 3 hp unit has twice as much filter area. One of the big restrictions with dust collectors is how much air they can exhaust. If you can exhaust twice as much air through the filters, you can move a lot more air with your DC. Twice as much surface area implies twice as much air flow. I'm sure it isn't that simple, but you get the idea.

The larger airflow also makes the motor work harder. The larger motor on the 3 hp DC is required to handle the extra work.



If you only use one set of bags on the 3 hp unit, you'll cut the filter area in half, effectively converting it to the same capacity as the 2 hp unit. You'll move less air and have unused motor capacity. It will look cool, though.

To further confuse issues, I have personally used a 3 hp DC with Wynn filters and Thien baffles. It didn't really work as well as I'd hoped. My previous experience was with a Jet 1.5 hp DC with Wynn filter and Thien separator. It worked great and i rarely had to clean the filter. The 3 HP units just move too much air for a Thien filter to work, however. Thien separators (brilliant inventions and thanks to Phil for sharing these with us) work by slowing the air enough for the fine dust to fall out. As the air flow increases, I don't think it can slow enough for this to take place. That was my experience, anyway. I had high hopes, but found myself constantly cleaning the filters. I guess I could have decreased the airflow to make it work better, but that defeats the purpose.

Having said all of that, a 2 hp DC with Wynn filter and Thien separator should work fine for you. What would work even better would be a 3 hp DC, vented outside. Since you live in a pretty temperate climate, you could easily pull this off as long as your next door neighbors aren't too close. That would give you an inexpensive DC with stellar performance and no filters to clean. I decided to vent outside a few years ago and have zero regrets.

Thanks for the response David. Venting outside would be a challenge for me. I would have to cut through brick, and I am sure the boss would frown at that idea. The next concern would be make-up air for all that air that is being pushed out of the house (my shop is in my basement). I don't know enough about the possible depressurization problem without doing some research.

Any thoughts on the make-up air/depressurization concern?

[david brum]

I know that it's a leap of faith. I held my breath when I cut holes in the side of my garage. The benefits are huge though, as is the cost savings when you look at the performance you're getting for the dollar.

As far as makeup air, it depends how tightly insulated your space is. My garage leaks enough air around the garage doors that it's not a problem. In a basement, you might need to partially open a window or design a vent.

[Lou Stags]

I know that it's a leap of faith. I held my breath when I cut holes in the side of my garage. The benefits are huge though, as is the cost savings when you look at the performance you're getting for the dollar.

As far as makeup air, it depends how tightly insulated your space is. My garage leaks enough air around the garage doors that it's not a problem. In a basement, you might need to partially open a window or design a vent.

My wife coming home to see that I drilled a 6 inch hole through the brick for "dust collection" is way more than a leap of faith! That smells like a month of sleeping on the couch to me :)

My house/basement is extremely well insulated and air-tight. My shop also does not have any windows in it - just a 36 inch door to the outside. So I would need to leave my door open - or drill another hole(s) for a vent. Leaving my door open does not sound like the best idea as it gets cold in the winter, and warm in the summer. Not to mention it is relatively humid in East Tennessee and I would be pulling in all that moist air from outside.

Based on your comments regarding the poor performance of the 3HP unit with the Thein baffle, it looks like my choice is the Grizzly 2HP unit (with Wynn filter and Thein Baffle) or a Cyclone. The 2HP option saves me some nice money that I can use on other tools but doesn't get me the performance I would get from a 3.5HP cyclone. If I were to buy a cyclone, it would be the 3.5HP unit from Penn State Industries.

I estimate I would save ~650 dollars going the 2HP/Thein Baffle/Wynn Filter route as compared to the 3.5HP Penn State Cyclone...

Hmmmmmmm..... Thoughts????

[David Kumm]

If not getting a full cyclone I'd get a 3 hp 14" impeller bagger and put oversize bags on it. American Filter or Beane Filters. Extra cloth area and can be swatted with a broom to release the dust inside. I would not put a cartridge on a 3 hp bagger with no cyclone if front of it. If you get enough filter area you can still get good filtration but not with stock bags. Dave

[Lou Stags]

If not getting a full cyclone I'd get a 3 hp 14" impeller bagger and put oversize bags on it. American Filter or Beane Filters. Extra cloth area and can be swatted with a broom to release the dust inside. I would not put a cartridge on a 3 hp bagger with no cyclone if front of it. If you get enough filter area you can still get good filtration but not with stock bags. Dave

Do you happen to know any 3HP units that have 14" impellers? The grizzly 3HP has a 12 3/4" impeller on it.

[david brum]

The big advantage of a larger cyclone is that they can handle long ducting, so can be stationary. To get good performance out of a 2 hp DC, you'd ideally want to wheel the DC to each machine. It pretty much depends on what your needs are.

[joe milana]

Yep, 2hp with 10-20 feet of even 6" ducting gives marginal performance at best, and I agree with Dave's suggestion of bags over cartridges. I "upgraded" to a cartridge from low quality bags, and have been disappointed. I am constantly having to clean out the cartridge. If I would have known of a source for high quality bags, I would have gone that route.

[David Kumm]

Do you happen to know any 3HP units that have 14" impellers? The grizzly 3HP has a 12 3/4" impeller on it.

Check with Grizzly. That unit says radial fan. If it has straight blades it will be smaller diameter. If it is designed to match the motor and impeller putting larger better bags will still work. A straight blade fan will be louder but will deliver cfm at higher SP so it will be smaller than a backward curved blade. Dave

[Lou Stags]

If not getting a full cyclone I'd get a 3 hp 14" impeller bagger and put oversize bags on it. American Filter or Beane Filters. Extra cloth area and can be swatted with a broom to release the dust inside. I would not put a cartridge on a 3 hp bagger with no cyclone if front of it. If you get enough filter area you can still get good filtration but not with stock bags. Dave

I checked out both websites (American Filter and Beane)... Looks like they are both in need of a desperate re-design of their circa 1998 web sites. Couldn't really get detailed info on how well those bags filter. I looked earlier and I think one of the sites indicated they are 1 micron bags. Any ideas on the specs?

Also - would you put a Thien baffle in front of the 3HP unit?

[David Kumm]

I've seen specs but 1 micron is about right. Bag specs change as they season. Keep in mind that sanding with 240 grit creates 2-5 micron and larger so you really have to be into something finer to get to sub micron dust when woodworking. Dave

[Lou Stags]

I've seen specs but 1 micron is about right. Bag specs change as they season. Keep in mind that sanding with 240 grit creates 2-5 micron and larger so you really have to be into something finer to get to sub micron dust when woodworking. Dave

Thanks for the response David. What are your thoughts on putting the Thien baffle in front of the Grizzly 3HP unit. I would put high quality bags on it. Another poster said the 3HP unit was too powerful for the Thien baffle to work effectively.

Does you (or anyone else) have thoughts on the 3HP unit being too powerful for the Thien baffle to work effectively?

[David Kumm]

I hope Phil responds as he knows best. I've got a four bag 7.5 hp Coral I use mainly for a big wide belt but would be interested if it would work as well. I'm running 2400 cfm to the WB. Dave