Good blower for dust collection?

[steven pratt]

Hey guys, new member here. I have a relatively small workshop in my basement and want to setup a dust collection system to run one machine at a time. What I have in mind is a 4" hose from the power tool to the dust separator (maybe 12' total length), then exits the dust separator as 4" duct but immediately increases to 6" diameter, then runs a length of 8' before it exits outdoors. I should be able to limit the 6" ducting to one, or at the most two, 90* elbows.

I've begun searching for just a blower. I've seen Bill Pentz's plans but I really don't want to build one. I've installed a couple Fantech units in my home so these came to mind however the CFM seems to max out around 650 and they require a 10" duct which I don't have room for, so a traditional blower seems like a better choice providing the CFM ratings are accurate. This is all new to me so I was hoping to get some recommendations and feedback on some blowers that might fit my application. A couple quick searches online didn't turn up many results for a la carte dust separator blowers.

Thanks.

[Joseph Tarantino]

check out this set up:

http://lumberjocks.com/topics/44313

that's with a HF blower motor sitting atop a thien separator. those HF DCs are currently available for $150. HFs not the best, but it'll get you started for a reasonable cost.

[David Kumm]

Hopefully Michael will chime in but you need to size the blower correctly. the 12' of flex adds a fair amount of resistance as does the separator- I'm assuming trash can type. The HR is not a good choice if it is a forward curved blade design as some are. Great cfm at low pressure but falls off dramatically at higher resistance. I'm guessing 2 hp 12" minimum. Backward inclined will be more efficient at low pressure, straight blade at higher but at an amp cost. Due the math on the pressure losses with the flex and pipe, add about 2" for the separator and calculate the total pressure drop. Look at some fan curves to see what cfm you can expect at that SP. Dave

[Michael W. Clark]

Welcome Steven,
If you want to spec out a fan for your application, you need to look at the machines and figure out which one requires the most CFM and how much. Depending on the machine, a 4" duct may be too restrictive. Good choice on up-sizing after the collector to save HP.

Also note the usual issues with venting outside if you do not bring in make-up air to the space. Not sure if this is an issue for you.

Mike

[steven pratt]

Thanks for he replies guys.

check out this set up:

http://lumberjocks.com/topics/44313

that's with a HF blower motor sitting atop a thien separator. those HF DCs are currently available for $150. HFs not the best, but it'll get you started for a reasonable cost.

If I had the floor space I'd probably consider something like that. Looks like a well thought out design. I just don't have the real estate though, and I'd rather not have to clean bags.

Hopefully Michael will chime in but you need to size the blower correctly. the 12' of flex adds a fair amount of resistance as does the separator- I'm assuming trash can type. The HR is not a good choice if it is a forward curved blade design as some are. Great cfm at low pressure but falls off dramatically at higher resistance. I'm guessing 2 hp 12" minimum. Backward inclined will be more efficient at low pressure, straight blade at higher but at an amp cost. Due the math on the pressure losses with the flex and pipe, add about 2" for the separator and calculate the total pressure drop. Look at some fan curves to see what cfm you can expect at that SP. Dave

Yep, it's a trash can style. Good info on the impeller design!

Welcome Steven,
If you want to spec out a fan for your application, you need to look at the machines and figure out which one requires the most CFM and how much. Depending on the machine, a 4" duct may be too restrictive. Good choice on up-sizing after the collector to save HP.

Also note the usual issues with venting outside if you do not bring in make-up air to the space. Not sure if this is an issue for you.

Mike

My machines are:
1) CNC Router
2) Shopsmith, used as a table saw and disc sander
3) 4" Jointer
4) 13" thickness planer
5) 14" bandsaw

I've read that a machine typically requires in the neighborhood of 4-500 CFM. I'm only going to run one machine at a time, however; the Shopsmith has a horrible dust collection design so the more CFM at this machine the better.

This blower looks interesting:
http://www.pennstateind.com/store/DC250SEMB.html

I sent them an email asking what type of impeller design it uses (maybe you guys can tell from the picture?).

[David Kumm]

Steven, take a look at ebay for blowers as well. Download a Cincinnati fan cfm table for their PB or PBS,SPB series and see the numbers for the various size blowers and designs. You can then reference the numbers with what you find used or compare to the Penn State blower. The relevant parts of the table will be 6-10" SP. The blower is the hardest working motor in the shop so it also pays to look for a good one. Talk about motor quality to whoever you buy from. Dave

[Michael W. Clark]

Depending on your CNC router setup, it may be the most challenging. A small table top unit may not be too bad, but a 3HP router unit could require more CFM and/or a high SP. You would have a flex going to the head and the hose will get sharp bends in it due to the movement of the head. A flow of 500 CFM will probably work on the planer and bandsaw, but more may be desirable. A typical cabinet saw benefits from about 800 CFM, not sure how the Shopsmith is setup for DC.

Mike