Is gravity a negligible force in dust collection?

[Zach England]

Sorry for such a pedestrian question, but I can't find much in a search. I have a 1.5 HP dust collector that I am trying to use with some long runs and I am just not getting the power I need. I am in the process of replacing all the spiral-type hose with rigid ABS drain pipe (yes, I know about grounding) and I am wondering if there will be a negative effect from running the pipe on the ceiling. Right now I just have a zillion hoses snaked all over the place, but what I'd like to do is run the ABS to two central locations in the ceiling, then connect my blast gates there and have short runs to the machines I need. Before I had the hose running along the ceiling, then I dropped it down to machine level (along the outer walls of a "shelf" basement) and got better suction, but this might be because I reduced the number of sharp turns.

So, will I sacrifice power by running the pipe on the ceiling, as opposed to three feet off the ground?

[Rod Sheridan]

Yes, but only if the pipe run has higher frictional losses.

If your new piping system has lower frictional losses than those awful flex hoses, you'll actually improve the performance.

Regards, Rod.

[Robert Parrish]

Have you sealed your system? I have mine mounted to the ceiling and didn't have as much suction as I thought I should. I then sealed the entire system with aluminum duct tape and it made a big difference. I'm using spiral steel also with 1 1/2 HP.

[Greg Peterson]

You may be asking your DC unit operate outside its design parameters. 1.5 hp is a pretty small unit to hook up to a duct system. Replacing the flex hose with smooth walled ducting will certainly increase the performance. Reducing the number of bends will also yield better results.

In the end however, you may find your DC unit too small to run a ducting network. DC is about moving high volumes of air. Even on a good day, all themselves, 1.5 hp DC units don't move a lot of air. Hooking up a network of ducting or spiral hoses further reduces their performance.

[Chris Friesen]

Gravity is *not* a negligible force. According to Bill Pentz's website, you need about 2800FPM in horizontal ducts to keep the dust entrained, but 4000FPM in vertical ducts (and even more for heavy compact chips).

I agree though, 1.5HP (even the Delta 50-760) is pretty marginal for any significant amount of ducting.

[Zach England]

Unfortunately I am pretty limited with what I can do now. I am not ready to tear into the electrical and I don't think it makes sense to upgrade the DC without having an available 220v.
I would love to move the DC unit between machines, but it is absolutely impossible. I was barely able to wedge it into the corner it is in and the ceiling is so low that the top bag cannot inflate fully. If I ever want to move it out of its current location I have to move my jointer and band saw. I cannot emphasize enough how tight the space is.

The runs are relatively short--none longer than 15 linear feet. I think I'll abandon the idea of running pipe along the ceiling because it sounds like that 9.8 m^2/second is more loss than I can afford. I can't run along the floor because I can't spare the room the pipe takes up (yes, that tight). I can run them along the shelf of the basement, which seems like the only thing I can do. I'll come back with more dumb questions soon.

[Greg Peterson]

You may want to consider installing a Wynn Environment cartridge filter on your DC unit. It'll give you better performance all the way around (less back pressure and capture finer particles). I think the cartridge is shorter than a bag, too. If your bag isn't able to fully inflate without hitting the ceiling then your bag is further restricting the amount of air it can flow. Whatever portion is pressed against the ceiling is blocking air from flowing out.

[Rod Sheridan]

Zach, there aren't any dumb questions, however I suggest you design your ducting and then check the fan curves for your dust collector to see if it will work.

There's not much point in investing all that time and money only to find that your collector can't deliver the airflow.

Regards, Rod.

[Steve Peterson]

Gravity will have no affect on the air moving through the pipes. Air pressure is essentially the same at ground level and 10 feet up. It takes an insignificant amount of energy to lift air 10 feet.

Small dust particles are easily suspended and can be considered to be the same density as air. Only large particles should be affected by lift. They may travel slower on the way up, but then give that energy back on the way down.

Therefore, the only loss should be if your pipe is in the basement and the DC is upstairs. The loss would be equivalent to the total mass of the sawdust lifted times the height difference between the source and the destination. The mass of any normal amount of sawdust is insignificant relative to the power of a 1.5HP motor.

So yes, I believe that gravity is a negligible force in dust collection.

Steve

[Zach England]

Zach, there aren't any dumb questions, however I suggest you design your ducting and then check the fan curves for your dust collector to see if it will work.

There's not much point in investing all that time and money only to find that your collector can't deliver the airflow.

Regards, Rod.

If nothing else it will FORCE me to run my 220 and upgrade the unit.

[Rod Sheridan]

If nothing else it will FORCE me to run my 220 and upgrade the unit.

Very good:D

Regards, Rod.

[Kent A Bathurst]

More than gravity, I'd think the rise up to the ceiling and then back down would have a bigger effect - just cumulative LF of the run - you are paying for the same real estate twice, rather than zero.

FWIW - I have one main stretch that runs across the floor. I haven't tripped over it in nearly 5 years. Quick connect on one end, so when I'm not going to use it for a while, I pull it out of the way. Doesn't bother me - but I lose every 1-1 tie vote around these parts.:D

1 foot flex = 2 feet to 3 feet of rigid (depending on which wizard you're reading). Sharp turns bad.

I do have a dumb question - don't hit me - do you have a blast gate on each machine? In other words - only one open air path at any given time?

Also - I used to be in the "PVC = static electric build up = KA-BOOM" camp, but everything I've been reading for a while says that's nuts. I don't have any PVC, so I don't have any skin in the game, just sayin.........

[Curt Harms]

I have a "2 h.p." Penn State D.C. 12" blower hooked up to a small ducting system. I agree with get rid of as much corrugated hose as possible. I'm not sure of the exact ratio but recall something like 10' flexible hose=30' of smooth ducting. If your flexible hose is 4", that's a double whammy. Avoid Ts if you can; I used 2 45 elbows with about 1' straight in between. I probably have 2 20' runs of 6" PVC (no, hasn't blown up even once yet;)) and blast gates all around. Each of the branches has 10' of 6" hose, I couldn't figure out a way to avoid it because everything is on wheels. I had room enough to run my ducting along the walls and put the D.C. in the corner. I had to get a little creative on how the two lines join but it has worked out well. The upshot is, I have a fixed D.C. setup that I'm happy with. Oh--I strongly recommend a Thien baffle and a good filter, either cartridge or high capacity fine filtration fabric filter. You can search under my name and Thien as a keyword should bring up my posts if you're interested.

[Zach England]

Thanks for the suggestions. Please keep them coming. Here is a little bit of an idea of the space I am dealing with. You can see the DC behind the band saw and jointer. The table saw is in the middle and one "trunk" runs to the table saw and to a cleanup hose by the bench and the other runs to the jointer, planer, and other small tools around the "shelf". The ceiling is about 6.5 feet tall at the bottom of the joists and the beam (above the DC) is about .5.5 feet off the floor. The total space, sans the "shelf", is about 10x10. I am kind of embarrassed to post the pictures, truthfully, but I thought it might help people suggest ways to improve the DC. You guys with garages or decent sized basements must think this is absurd.

Thanks again.

[Kent A Bathurst]

[QUOTE=Zach England;1366855.....You guys with garages or decent sized basements must think this is absurd.....[/QUOTE]

Heck NO!!. I'm in awe - you're playing the hand you were dealt. I'm gonna have to start calling you "Sir". Press on regardless - I love your attitude.

Throw el-cheapo plastic blast gates on everything and run just one open line at a time. Organize/straighten lines if + where you can. Hunks of rigid if + where you can - but I wouldn't spend a lot of $$ on that - JMHO - it is not physically possible for the dust source to be very far from the DC.

[Zach England]

Heck NO!!. I'm in awe - you're playing the hand you were dealt. I'm gonna have to start calling you "Sir". Press on regardless - I love your attitude.

Throw el-cheapo plastic blast gates on everything and run just one open line at a time. Organize/straighten lines if + where you can. Hunks of rigid if + where you can - but I wouldn't spend a lot of $$ on that - JMHO - it is not physically possible for the dust source to be very far from the DC.

Problem is I wasn't into woodworking when I bought the house. I also once raised chickens in the same space, so that might indicate a further measure of insanity.