Dust Collector - One 6" Intake VS Two 4" Intakes

Hi folks. I'm designing a central dust collection system for my one-car garage shop, using the HF 2HP collector. I'm trying to decide between using one 6" main line with 4" branches, or two 4" main lines with 4" branches. My shop is set up such that all the tools that require dust collection occupy the back half of the room. Picture the tool layout forming a "U" along the perimeter of the side and rear walls. My dust collector is in the bottom left corner of the "U". I figure I can either use two 4" main lines, sending one along each side of the "U". Or I could use one 6" main line and run it up the wall and across the middle of the ceiling, sending branches out to each tool. Using two 4" main lines would make the run easier because I'd only be using the perimeter of the room, but I don't want to make a large sacrifice in dust collection efficiency. Any suggestions would be greatly appreciated!

Joe

Others may disagree, but my general rule is to use main line ducting the size of the DC intake. If yours is 6" with an adaptor to two 4's, I would use a 6" main with appropriate drops. Some drops may be larger than 4". My table saw, for example, takes a 5.

As far as the setup in your shop, keep the runs as short as possible. I am assuming you are using one tool at a time.

Welcome aboard, Joe,

Rick Potter.

If it were me, I'd do the 6" main with 4" drops, unless doing so means making the lengths longer and increasing the # of bends to the critical dusty tools than if left to 4"

I would send a 6" main in both directions. You won't run multiple machines and a 4" main with knock the CFM way down due to the pipe resistance. Avoid as much small diameter pipe as you can. Dave

I already bought the dust collector, but haven't opened the box yet. Looking again at the specs online, it appears it has only a 4" intake with a 4x4 wye adaptor, rather than the more typical 6" intake with 4x4 wye adaptor. This, I suppose, makes using a 6" main line less effective since it will only bottleneck up at the DC intake. With this in mind, would there be any benefit to using a 6" main?

That wye is probably removable. There will likely be a 6" inlet behind it.

Go with a 6" main.

So it turns out the HF DC has a 5" intake behind the 4x4 wye adaptor , so it would be a 5" main line rather than a 6".

It seems 5" duct and fittings are not very common. Do most people using the HF DC use a 4" or a 5" main line?

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Originally Posted by Joe Montague

It seems 5" duct and fittings are not very common. Do most people using the HF DC use a 4" or a 5" main line?

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generally you will still be better off with a 6" horizonal and 4 or 5" verticals. The restriction right at the inlet is still better than the restriction of 5" pipe all the way. velocity of the main is your concern but a little slower flow on the horizontal is preferable to reducing velocity at the machine port. Just don't use a 6" vertical. Dave

When I had mine, I replaced the side piece of the DC with a piece of plywood and a 6" inlet. It seemed to work far better and was easier to find 6" parts.

The biggest problem with the HF DC is that it's impeller is too small and it really isn't 2 HP. More like 1.5HP.

The good news is that the price is a steal.

Throw the 2-4 adapter in the trash!

As mentioned, just remove the 5" takeoff from the DC housing and make one that is 6". I used a piece of 1/4" melamine, and a 6" duct takeoff that came from Lowes, I used the adhesive type, and backed up the adhesive with screws. I think I ended up using new bolts to attach it to the DC housing, as I seem to remember the originals being too short using the 1/4" melamine. Just be sure not to use bolts that are too long, they won't hit the impeller, but would likely cause turbulence and impede material flow. A separator is also something you will want to think about. It will removed the chips and the majority of the dust before it gets to filter, there by keeping the filter clean and allowing maximum flow. Also, fine dust smaller than the micron rating of the filter that doesn't reach the filter won't get through it. I built a "top hat" design that sit atop a trash can, and dump it instead of the collection bag. My collection bag barely gets the slightest bit of dust in it.

As Alan stated the impeller is smaller than most, measuring 9.75", but the 12" impeller from a Rikon 60-200 DC is a perfect and easy direct fit replacement. It was $60 + shipping when I got mine.

I ran with the stock Y-branch 4" pipes in 2 directions. My DC is the 1 1/2HP Delta with canister filter on top. The longest run is about 25 feet from the branch feeding the TS. The short side goes straight to the jointer/planer. Blast gates in either direction which can be closed off easily to the branch not in use. I went this way as the Delta is not the most powerful and most info that I have read shows this to be the best arrangement for a unit with limited CFM and not a cyclone.

Joe, I ran two 4" ducts from my 1.5HP Jet (in the interest of time and money) but am planning to upgrade to 6" to get better flow. I would have been better off to have done 6" from the start like you are considering and others are suggesting above. If you can upsize your machine ports, you will realize the full benefit of the 6" duct, otherwise you take a big hit on that restriction.

Adding a pre-separator will help get the heavy dusts out, but it will also cost you on flow at the hood. The separator has a pressure drop associated with it and will therefore reduce the fan volume. You will get less CFM with the separator than you would without it. Since your impellor is small already, I would not opt for the separator to get more CFM at the hoods. A 6" 90 elbow is only about a 1/4" of loss at 750 CFM. If the separator is only 1" of pressure drop (probably more), then it would be like adding (4) 6" 90s to the system. If you have to reduce down to 4" at the separator, then you have even more loss.

Mike

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Originally Posted by Alan Lightstone

When I had mine, I replaced the side piece of the DC with a piece of plywood and a 6" inlet. It seemed to work far better and was easier to find 6" parts.

The biggest problem with the HF DC is that it's impeller is too small and it really isn't 2 HP. More like 1.5HP.

The good news is that the price is a steal.

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I did something similiar on my Grizzly, except I bought a 6" inlet from one of the big box stores and used a metal cutting blade on my saber saw to cut the opening larger. Used foam tape and sheet metal screws to attach the inlet to the plate and then remounted the plate on the DC. I then made sure the impeller didn't hit anything and then powered it up. All my main ductwork now starts at 6 inches and gets reduced from there.

One 6" duct will have lower pressure drop per foot of duct than two 4" ducts. The small part is because the 6" has more cross-sectional area than the two 4" ducts combined but mainly because there's less pipe surface area to develop the friction. Make the Y as close to the tool as is feasible.

Just my opinion.. YMMV.

Jim

Here's a picture of mine (boy, had to dig to find the picture of it):
Attachment 232938

Great ideas, guys! I think I'm going to enlarge the hole on my DC to accomodate a 6" inlet. Does anyone know of a larger impeller that is a drop-in replacement for the stock impeller?

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Originally Posted by Joe Montague

Great ideas, guys! I think I'm going to enlarge the hole on my DC to accomodate a 6" inlet. Does anyone know of a larger impeller that is a drop-in replacement for the stock impeller?

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I guess you missed my ealier post......

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Originally Posted by Kevin W Johnson

As mentioned, just remove the 5" takeoff from the DC housing and make one that is 6". I used a piece of 1/4" melamine, and a 6" duct takeoff that came from Lowes, I used the adhesive type, and backed up the adhesive with screws. I think I ended up using new bolts to attach it to the DC housing, as I seem to remember the originals being too short using the 1/4" melamine. Just be sure not to use bolts that are too long, they won't hit the impeller, but would likely cause turbulence and impede material flow. A separator is also something you will want to think about. It will removed the chips and the majority of the dust before it gets to filter, there by keeping the filter clean and allowing maximum flow. Also, fine dust smaller than the micron rating of the filter that doesn't reach the filter won't get through it. I built a "top hat" design that sit atop a trash can, and dump it instead of the collection bag. My collection bag barely gets the slightest bit of dust in it.

As Alan stated the impeller is smaller than most, measuring 9.75", but the 12" impeller from a Rikon 60-200 DC is a perfect and easy direct fit replacement. It was $60 + shipping when I got mine.

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Originally Posted by Joe Montague

Great ideas, guys! I think I'm going to enlarge the hole on my DC to accomodate a 6" inlet. Does anyone know of a larger impeller that is a drop-in replacement for the stock impeller?

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Joe, I'm not discouraging you from enlarging the inlet because I believe you will receive some benefit but enlarging an inlet or or replacing a fan within an existing housing will not automatically improve your life. There are relationships at play that require lots more knowledge than I posess to ensure increased cfm or efficiency. A fan will be designed for a maximum intake size based on the blade configuration and while a smaller inlet just reduces the cfm a larger opening may reduce efficiency so the cfm delivered comes at a greater relative amp draw if at all. The same thing occurs when changing fan diameter within a housing. The limitation will be the size of the housing plate which is usually not much bigger than the stock fan. Dave

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Originally Posted by David Kumm

Joe, I'm not discouraging you from enlarging the inlet because I believe you will receive some benefit but enlarging an inlet or or replacing a fan within an existing housing will not automatically improve your life. There are relationships at play that require lots more knowledge than I posess to ensure increased cfm or efficiency. A fan will be designed for a maximum intake size based on the blade configuration and while a smaller inlet just reduces the cfm a larger opening may reduce efficiency so the cfm delivered comes at a greater relative amp draw if at all. The same thing occurs when changing fan diameter within a housing. The limitation will be the size of the housing plate which is usually not much bigger than the stock fan. Dave

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Ah, but the only difference between the HF DC and the Rikon 60-200 is the size of the impeller. I've studied the Rikon at Woodcraft, and I have the HF unit personally. For whatever reason, Harbor Freight chooses to use a smaller impeller, heck I guess it saves them $2 in material cost. Otherwise they are the same unit, and the impellers swap perfectly between the two.

I've personally put the Rikon impeller in mine as well. Running amp draw with the 12" Rikon impeller is 13 amps, which might be tenths of an amp different from the stock impeller at most. I checked it before and after, and the difference, if any wasn't note worthy.

Kevin, I agree with you and Joe. Just not wanting others to think they can swap pieces and automatically get a better result. 12" impellers are kind of the norm for a 2 hp motor. I think Oneida may even use a larger one but theirs is BI which limits the amp draw compared to a straight blade. I'm assuming yours is a straight radial? Dave

I tried getting a straight answer from Grizzly as to whether their impellers would work. I think it will, but they never would answer the question.

The drop in Rikon sounds promising along with the 6" inlet from Lowes.

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Originally Posted by Kevin W Johnson

Running amp draw with the 12" Rikon impeller is 13 amps, which might be tenths of an amp different from the stock impeller at most. I checked it before and after, and the difference, if any wasn't note worthy.

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Kevin,
If you are pulling more air with a larger impellor, why didn't the amp draw increase? Or do I misunderstand your post?

The HP (amp draw) varies greatly with CFM change. Granted, you may have a more efficient impellor if they are different design, other there should be a significant increase in HP.

Mike

There is a lot more to impeller performance than just the diameter. Width, angle, curvature and number of blades all affect the performance curve.

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Originally Posted by Michael W. Clark

Kevin,
If you are pulling more air with a larger impellor, why didn't the amp draw increase? Or do I misunderstand your post?

The HP (amp draw) varies greatly with CFM change. Granted, you may have a more efficient impellor if they are different design, other there should be a significant increase in HP.

Mike

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I would have thought that the amp draw would increase also.

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Originally Posted by Kevin W Johnson

I guess you missed my ealier post......

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Kevin, actually I DID read it. The funny part is, I thought I had read it somewhere else, and couldn't remember where I had seen it! I should've reread my own thread first! Thanks for that!

Kevin, did you buy the Rikon 12" impeller directly from Rikon?

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Originally Posted by Michael W. Clark

Kevin,
If you are pulling more air with a larger impellor, why didn't the amp draw increase? Or do I misunderstand your post?

The HP (amp draw) varies greatly with CFM change. Granted, you may have a more efficient impellor if they are different design, other there should be a significant increase in HP.

Mike

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Case of bad memory, and making too many changes to my DC system and not writing down any of my measurements.

So, to solve that I swapped the original impeller back in and took some measurements as measured by a Fluke 337.

On the original HF impeller, inrush = 68.5A running = 10.5A

On the Rikon impeller, inrush = 70.1A running = 12.2A

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Originally Posted by Joe Montague

Kevin, did you buy the Rikon 12" impeller directly from Rikon?

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Yep, Just call Rikon 877-884-5167 7:30am-4:00pm ET, and ask for parts, and you need the impeller for a 60-200 dust collector.

Seeing as how the vanes are reversed on those two impellers, which direction does the motor turn? are the HF and Rikon motors reversed from one another?

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Originally Posted by Kevin W Johnson

Yep, Just call Rikon 877-884-5167 7:30am-4:00pm ET, and ask for parts, and you need the impeller for a 60-200 dust collector.

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I called and tried to order the part, but Rikon requires the dust collector serial number for liability purposes. I suppose they did not ask when you ordered yours?

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Originally Posted by John Baranowski

Seeing as how the vanes are reversed on those two impellers, which direction does the motor turn? are the HF and Rikon motors reversed from one another?

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The blower housing would have to be reversed as well. Most larger ones allow for that. Kevin was that the case with yours? You can run a forward curved fan but not usually done in dust collection and this fan isn't designed for that. Dave

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Originally Posted by Joe Montague

I called and tried to order the part, but Rikon requires the dust collector serial number for liability purposes. I suppose they did not ask when you ordered yours?

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No, I didn't have that problem when I ordered mine.

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Originally Posted by David Kumm

The blower housing would have to be reversed as well. Most larger ones allow for that. Kevin was that the case with yours? You can run a forward curved fan but not usually done in dust collection and this fan isn't designed for that. Dave

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So your saying Rikon is using an impeller that isn't designed for dust collection? I bet that's news to them.

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Originally Posted by John Baranowski

Seeing as how the vanes are reversed on those two impellers, which direction does the motor turn? are the HF and Rikon motors reversed from one another?

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Incidentally, no that are not. The housings, motor, etc., are all excatly the same.

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Originally Posted by Kevin W Johnson

So your saying Rikon is using an impeller that isn't designed for dust collection? I bet that's news to them.

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Kevin, the Rikon unit is designed with a blower that runs the fan in a clockwise direction. Your original fan was designed to run CCW. If you didn't change anything you are running the Rikon backwards from what it is designed for. Dave

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Originally Posted by David Kumm

Kevin, the Rikon unit is designed with a blower that runs the fan in a clockwise direction. Your original fan was designed to run CCW. If you didn't change anything you are running the Rikon backwards from what it is designed for. Dave

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Really? Funny, seeing as the HF unit runs CW.

Both the Rikon and HF units are CW in their rotation (as well as Shop Fox W1685, W1666), as determined by the positioning of the motor on the housing. Units such as the Jet DC-1100, DC-1200, Delta 50-850A, Powermatic PM1300, are CCW units.

Kevin, if your HF blower is a clockwise configuration running a forward inclined blade you really improved it when in effect you changed to the more proper BI configuration. I have never seen a DC run a FI fan and would be surprised if the others you mentioned used FI blades. They will likely run fans made in the same direction as Rikon. FI fans are meant for low rpm, high volume but low pressure applications while BI fans are medium volume at higher pressures which is why the diameter is larger. The HR unit may pull great CFM unrestricted but the flow will drop dramatically when restistance from pipes is added. Turns out you did absolutely the correct thing in swapping the impeller. The original one is not correct for the application IMO. Dave

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Originally Posted by David Kumm

Kevin, if your HF blower is a clockwise configuration running a forward inclined blade you really improved it when in effect you changed to the more proper BI configuration. I have never seen a DC run a FI fan and would be surprised if the others you mentioned used FI blades. They will likely run fans made in the same direction as Rikon. FI fans are meant for low rpm, high volume but low pressure applications while BI fans are medium volume at higher pressures which is why the diameter is larger. The HR unit may pull great CFM unrestricted but the flow will drop dramatically when restistance from pipes is added. Turns out you did absolutely the correct thing in swapping the impeller. The original one is not correct for the application IMO. Dave

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which is what I was getting at. I figured the HF one was wrong.