Can I run 2 DC's in series

[Ramsey Ramco]

I just recently got the Hf dust collector rated at 2hp which I find very hard to believe, but it does a decent job with short runs and one machine open at a time. I got a coupon in a magazine yesterday for that same dust collector for $139.00 while about a month ago I spent $179.00, so what I'm asking is if there is any way to run the collectors in series or parallel that is if I were to get another one, and would that double the HP so I could run an overhead blade guard with DC and a few other machines as well. In that case I would be interested in 2 open gates at a time and nearly a 30' run so I can go up and over rather than on the ground. Another question is if there are any other ways to increase suction, I use a combination of pvc and flex to make turns, My shop now is about 25'x25' and tools requiring DC are spread throughout, so my plan is to permanently duct most likely with PVC, anything I need to know about grounding? I would think not being plastic but I may be wrong. Does adding a trash can cyclone help in this situation or will that just make it worse. Any info will help but if there is a way to hook 2 DC's together to double the power please include how I'm pretty new to dust collection in general, my old DC was a push broom dust pan and a trash can.:D

[Myk Rian]

I don't think running them in series or parallel is going to help any.

I have a HF DC and use 4" PVC throughout. I wrapped the pipe with wire to keep the hair on my arms from getting stuck to it. Grounded at the DC frame.

Use 45º fittings instead of the sharp bend 90º and 45º Wyes instead of T connectors. There are also large radius 90º connectors available.

Screw and tape the PVC connections instead of gluing the pipe together. That way you can make adjustments to it without sawing it apart.

[Robert Parrish]

Do you have room for two dust collectors? I'm in the process of adding a second DC to my shop and split them between machines. One (Jet 1100) will be used solely for my lathe and bandsaw while the other (Grizzly 2hp) will be for the chip producing machines. The Jet will be outside of the shop in another room.

[Jim O'Dell]

I wouldn't use in series as one fan pushing the other one might create a problem for the motor of the one being pushed. In parallel should be ok, but as alluded to, I'm not sure how much it would help. If they were both 4" input, and you could use 6" pipe for the system and split to the two 4" inputs for the collectors, you should be ok. Maybe you could be the test bed for others and try it??:D Jim.

[Dan Friedrichs]

The length of the runs is almost immaterial - if you're using large enough pipe (6" diameter), the resistance of the pipe is not a significant loss.

A single 2HP DC might do well enough by itself if you plumb everything correctly. That means using 6" pipe, no 90* turns, as little flex duct as possible, and upgrading the filters on the DC for more airflow.

Consider venting your DC outside, if possible - removing the filters from your DC will significantly increase airflow.

When laying out your plumbing, try to imagine that your pipes are designed to transport live hand grenades, rather than sawdust. You want them to get to where they're going quickly, with very little disturbance. Rather that using 90* elbows, use two 45* elbows spaced about a foot apart (this keeps the air from slamming up against the elbow by allowing it to turn gradually, instead). Flex hose of all sorts is bad, because the grenade gets shook up really badly every time it goes over all those ridges. Finally, the grenades are exactly 6" diameter, so you can't have any location in the plumbing that is less than 6" diameter, or they'll get stuck :)

Those may seem like trivial improvements (versus turning on another 2HP motor and blower), but they absolutely are not. I recently removed the piece of flex pipe between my blower and the bag ring (by mounting the blower on a stand in such a way that it directly connects to the bag ring without any pipe in between), and the improvement in airflow was HUGE.

Try disconnecting the inlet and outlet hoses to the blower, turning it on, and feeling how much air that blower (with nothing attached to it) will move. I think you'll see that it moves more than enough air for your needs - it's just a matter of removing the restrictions in your system that are limiting its potential.

[Ramsey Ramco]

Do you have room for two dust collectors? I'm in the process of adding a second DC to my shop and split them between machines. One (Jet 1100) will be used solely for my lathe and bandsaw while the other (Grizzly 2hp) will be for the chip producing machines. The Jet will be outside of the shop in another room.

Yes It will take a little rearranging but i will be able to fit 2 DC's. Most of my tools that would take up the most space are on casters and slide under one of the 3 work benches. Along the North wall I have a steel bench I use for welding and store my planer and router table. To the east I have my 60 gal. compressor and to the west I have my DC. On the south wall I keep 2 airless paint sprayers an HVLP system and my 6" jointer also under a bench. Plenty of wall cabinets for storage and then a combo out feed/assembly table in the center behind the saw and more storage. I might be set on another DC for my removable items, i.e the router table, jointer, planer, I know I need my TS with 2 ports, and my miter saw permanent, other than that I'm OK with pipes to the rough location and blast gates. I will attempt running 6" pipe, I am a contractor so I'll talk to a couple HVAC buddies and see what they can do on spiral pipe, and maybe a case of beer and steaks to help with the install. Any ideas, or pictures would be very much appreciated as well. I'm grateful for the input. A little stubborn though and not sure if I can pass up a $140 DC, now my miter station is hooked up to my shopvac. :D

[James MacArthur]

2? Try 3 :)

http://img.photobucket.com/albums/v621/Chems-/DSC00717.jpg

Works a treat and really does triple the suck.

[Ramsey Ramco]

2? Try 3 :)

http://img.photobucket.com/albums/v621/Chems-/DSC00717.jpg

Works a treat and really does triple the suck.
if its not too much trouble could you let me know how you wired it up and does it really help. also does it change HP rating if i wire to 220v instead of 110v?

[Ramsey Ramco]

to be honest I never thought of running all the blowers as well. I was leaning more toward 2 motors in line. If this works though please let me know

[Dan Friedrichs]

Ramsey,

It does not change the HP rating of the motor to wire it for either 110 or 220 - when you convert a motor to the "other" voltage, you series or parallel the windings within the motor, so the motor will "see" the same thing, for either voltage.

I'm not sure what you mean by "2 motors in line". Induction motors (the type found on typical dust collectors) run at a fixed speed (essentially). If you put WAY too much load on the motor, it will slow down (thus, moving less air), but otherwise, the speed is virtually constant. The fan part moves a fixed amount of air at a given speed. So adding additional horsepower doesn't do anything unless you increase the size of the fan. If you were to take the fan off your DC, and hook it to a 200HP motor, it would move the same amount of air as with the stock motor.

If you want to move more air, you need a bigger fan. In turn, that may require a larger motor to spin it. But without a larger fan, you'll move the same amount of air.

Not to rain on your parade, James, but I bet if you connected a ammeter up to those dust collectors, you'd find that they aren't using a fraction of the power they're supposed to. While they may be 1 or 2HP motors, the size of your main inlet duct limits the amount of air you can move, which limits the amount of work each fan can do, which limits the amount of work the motor does. Thus, your 2HP motor might only be delivering a fraction of a horsepower. You've essentially taken the work that could be done by one dust collector, and distributed it over three.

You may notice increased suction, but what you're really getting is increased static pressure (not increased airflow). A dust collector moves large volumes of air at low pressure (thus, it can move a lot of dust out of an area in a hurry, but can't lift a screw off the floor). A shop vac, for instance, has lots of static lift (it easily picks up rocks and screws), but doesn't move a large volume of air. If you want lots of static lift, you should buy a shop vac. If you want to collect dust, you need a dust collector which moves lots of air.

[Tri Hoang]

I'd have them in parallel config with a large, main input pipe...say 6".

[Alan Lightstone]

I keep thinking about doing the same thing. 2 HF DCs in parallel. I have 6" flexible pipe. Probably going to permanently change to metal piping.

I can't see how two in parallel won't improve airflow, but the wyes will add enough friction so that you won't get double the flow. Maybe 50% more (WAG), but isn't that still pretty significant?

Two DCs in parallel with 4" pipes probably won't do anything except increase the noise level.

[James MacArthur]

It doesn't work in parallel as one DC starves the other of air.

I did a very short video of my hand been sucked in, you can see the increased pressure I'm applying to remove my hand each time. It is very much 3 times the suck and very noticeable at the tablesaw with the amount of dust extracted from below the blade.

http://img.photobucket.com/albums/v621/Chems-/th_MOV00718.jpg (http://smg.photobucket.com/albums/v621/Chems-/?action=view&current=MOV00718.flv)

I'd love to say I came up with this brilliant idea but another guy from the UK forums was the trend setter. He put multi meters on it to check amps and even made a little home made suck measurer that measured doubled the speed. Read the thread here tells you all you need to know:

http://www.ukworkshop.co.uk/forums/dual-extractor-design-cyclone-install-t33161.html?highlight=dual%20extractor


All I can say is that it works, so have a go if you have 2 DC's to try it with.

[Dan Friedrichs]

It doesn't work in parallel as one DC starves the other of air.


Again, I think you are not thinking of "dust collection" in the same way as most people do. If you are "starving" one of your parallel dust collectors for air, that just means you don't have enough inlet area. Multiple dust collectors in parallel will move more air.

The particular type of impeller design used in most dust collectors, coupled with the speed of the motors typically used, results in a certain shape of "fan curve" - a plot that relates the pressure difference created by the fan to the volume of air moved by the fan. When you have maximum pressure, you have minimum volume being moved.

Thus, you might find that you can pick up a 1lb chunk of wood with a single dust collector, and a 2lb chunk of wood with 2 in series, etc - but you're still moving the same amount of air. Even with multiple series dust collectors, the air pressure is not enough to cause the air to compress, so any obstruction will limit the volume of air moved. With 4" ducting, you can move, at max, about 450CFM. Unless you get up to much, much higher pressures, you will always be limited to 450CFM with 4" duct.

What you've created is a 450CFM shop vac. If that's what you want - great. But to capture the fine dust generated by your woodworking tools, you don't want high pressure differences, you want lots of air volume to be moved. A typical recommendation is 800CFM. You absolutely cannot get that with 4" duct (unless you have a ridiculously large motor and blower).

While you feel more "suck" with multiple dust collectors, it's only because the static pressure is being increased. You are still moving the same volume of air. Intuitively, that's not what you want for dust collection - imagine you're trying to air out a smokey kitchen: You could set your air compressor in it, and dangle the open hose outside. It can generate an output that it very high pressure, but will take forever to clear out all the smokey air because it moves very little volume. What you really want is a large fan, which doesn't generate much pressure (you certainly can't inflate a car tire with a household fan, for instance), but DOES move a large volume of air.

A similar example is with water. When you're drinking a beverage with a straw, what size straw do you want? If you find one that's 0.5" diameter, you'll find you can easily move a large volume of liquid into your mouth without sucking on it very hard. If you find a straw that's 1/32" diameter, you'll have to suck very hard, and even sucking as hard as you possibly can (generating lots of pressure), you won't be able to move as much liquid as with the larger straw.

[James MacArthur]

I see what your saying dan, the aim was not to increase the amount of air moved but to increase the amount of dust captured due to a higher "suck" if this makes sense?

For instance, if I lay the end of my 4" hose on the table, and put a few specs of dust and plane shavings down and start up one fan with for example the shavings and what not 5 inches away, it won't suck them in, but turn on the others and it will. Thats what I was aiming for to capture the most amount of dust inside my table saw cabinet to stop it coming out of the front of the saw and such. And it does very much work. Beyond that I can't really say if its what you are aiming for originally.

[Alan Lightstone]

Still having trouble getting my head around this one.

Through the same size pipe, doesn't increased pressure mean increased flow?

And what would happen with the increased pressure if you then increased the size of the pipe from 4"to 6"?

[Dan Friedrichs]

I see what your saying dan, the aim was not to increase the amount of air moved but to increase the amount of dust captured due to a higher "suck" if this makes sense?


Then I think we're just disagreeing on what "dust" is. You're talking about "chips" - most people would use a shop vac to clean those up. While most dust collectors will pick up those chips, chip collection is perhaps of secondary importance to dust collection (ie - collecting very fine dust). The fine dust is a health hazard when you inhale it, so you want to move a very large volume of air through your filters to remove as much as you can from the air that you're breathing. Thus, you want lots of air moved.

Chips of wood are not much of a health hazard, as their size makes them hard to inhale :)

[Dan Friedrichs]

Still having trouble getting my head around this one.

Through the same size pipe, doesn't increased pressure mean increased flow?

And what would happen with the increased pressure if you then increased the size of the pipe from 4"to 6"?

Take a look at a "fan curve" for a typical dust collector - as the pressure increases, the volume decreases. If you put your hand over the end of a shop vac hose, you'll feel lots of suction (ie - a large pressure difference), but no air is being moved. The existance of pressure implies that there is resistance to air flow, which limits volume.

If you increase the duct size from 4" to 6", pressure will go down, but volume will go up (which is what you want for dust collection).

[James MacArthur]

Then I think we're just disagreeing on what "dust" is. You're talking about "chips" - most people would use a shop vac to clean those up. While most dust collectors will pick up those chips, chip collection is perhaps of secondary importance to dust collection (ie - collecting very fine dust). The fine dust is a health hazard when you inhale it, so you want to move a very large volume of air through your filters to remove as much as you can from the air that you're breathing. Thus, you want lots of air moved.

Chips of wood are not much of a health hazard, as their size makes them hard to inhale :)


Yes I see what your saying, I still have the coarse filter bags on my DC unit, been meaning to get a proper metal top filter one. I do want to catch more dust, not chips as at the moment I don't have a Jointer I just want good collection on my TS and any other tools that will take 100mm (4 Inch) connection.

[GLENN THOMAS]

I don't know about dust collectors but the concept works with water pumps on fire engines. When to pumps are connected in a series the pressure increases. When two pumps are connected parallel the volume increases. We have a lot of two stage pumps in the fire service, the pumps have two impellers and a transfer valve. By changing the transfer valve we can go from series to parallel. I don't know for sure but seems like the concept should work for DC as well.


GT

[James MacArthur]

Hey Glen, I'm a firefighter in the UK, we have 2 stages pumps on all appliances but can't think of anything off the top of my head like you said. But we do of course use multiple pumps in series to make a water relay and each pump increases the pressure as it flows along so I guess thats what I'm doing.

On a side note, I was in NY at Christmas and was invited into the Lions Den, somewhere near central park it was, and there pumps looked a lot more complicated than ours but not as new as our kit but by far an away cooler to ride around on!

[Mark Beall]

I don't know about dust collectors but the concept works with water pumps on fire engines. When to pumps are connected in a series the pressure increases. When two pumps are connected parallel the volume increases. We have a lot of two stage pumps in the fire service, the pumps have two impellers and a transfer valve. By changing the transfer valve we can go from series to parallel. I don't know for sure but seems like the concept should work for DC as well.


GT

There is a big difference between pumping a fluid (be it a gas or liquid) and using suction to pull a fluid. Although you can use a pump (or pumps) to get pretty much any pressure difference you want, the most you can get with suction is about 15 psi, since then you have a perfect vacuum.

mark

[GLENN THOMAS]

There is a big difference between pumping a fluid (be it a gas or liquid) and using suction to pull a fluid. Although you can use a pump (or pumps) to get pretty much any pressure difference you want, the most you can get with suction is about 15 psi, since then you have a perfect vacuum.

mark

Mark,

You are 100% correct. Guess I jumped into this without thinking it through all the way. Im thinking in terms of discharge when the issue is intake. DUH !!!

[James MacArthur]

But very similar to lifting water, we can pump water up hundereds of feet in the air but we can only lift water from 8 meters below.