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HF 2hp DC - permanent ductwork

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Forum topic by live4ever posted 1344 days ago 2450 views 1 time favorited 21 replies Add to Favorites Watch
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live4ever

983 posts in 1647 days


1344 days ago

Topic tags/keywords: question dust collection harbor freight duct

My plan has been to permanently plumb my HF 2HP DC with 4” PVC. This way I won’t have to drag the DC around my shop and will be able to put the DC in a place where it will generate the least amount of noise for my neighbors (attached houses).

I finally read Bill Pentz’ site, which I had resisted for a long time because I knew I wouldn’t like what he had to say.

His take on the HF 2HP DC is that the impeller is too small, and that one shouldn’t even bother hooking it to permanent ductwork because it won’t be able to overcome the static pressure loss of such a ducting system.

So my question to you guys who are using this DC to power your permanent dust collection:

1) What diameter ductwork are you using?
2) What is your longest ducting run, and do you get adequate collection at the tool?
3) Do you have any problems with clogged ducts/inadequate airflow?

After reading all the info on Pentz’ site, I’m wondering if I should even bother with the effort of permanently ducting this DC…

-- Optimists are usually disappointed. Pessimists are either right or pleasantly surprised. I tend to be a disappointed pessimist.


21 replies so far

View crank49's profile

crank49

3380 posts in 1608 days


#1 posted 1344 days ago

The HF DC comes with a 5” x 4” x 4” wye fitting on the fan inlet. I connected a 4” pipe to one side of this wye with a balancing damper and this handles the dust from either my table saw or jointer. I reduced the other side to a 2-1/2” size and connect this side to my belt/disk sander or to my little 10” band saw. I am very happy with this set-up and it works just fine. I do intend to put a homemade LE cyclone or dropout box in the 4” line to reduce the amount of debris that passes through the fan impeller, but that is a wear and tear issue, not a collection issue. My longest run is about 28 ft with 4” pipe with three 90 degree sweep ells and one 45 degree.

By the way, I have read Bill Pentz’s site as well. He makes some sense, but i can’t say I agree with every thing he says. I have been an engineer in a foundry environment for over 30 years. I have designed and built bag and cartridge dust collection systems that handle 1000 CFM to over 300,000 CFM and have multiple 250hp fans. For what it costs and for what it’s designed for there is nothing wrong with the HF collector. It has plenty of static pressure and CFM to handle the duty of a small wood shop. I would not put it into an industrial system because it is not industrial duty, but for home use it is perfect. By the way, a true industrial duty 600 CFM collector would cost about $4 per CFM, or $2400, so I would not put any of the HF competitors in this class either.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

View live4ever's profile

live4ever

983 posts in 1647 days


#2 posted 1344 days ago

Thanks, Crank & Charlie. Crank, your longest run is almost the length of my longest run, so that gives me hope. I figure I’ll get the goods to set up the long branch and see how it goes.

Charlie, I probably should be running 6” line all the way around, if I am to do things as Pentz suggests. However, using 4” PVC makes my life a lot easier and makes this endeavor a bit cheaper. When I have the space and money one day to have a large shop that is only a shop, I’ll be running larger ductwork.

As for the separator, Pentz does incorporate a separator into his static pressure calculations – a trashcan separator adds 4.5” of static pressure drop. Here’s where I have trouble understanding the calculations though. What do you do with the static pressure number? For instance, if the calculated static pressure drop for my longest branch is 7”, how do I know if that’s ok or too much for this particular DC??

-- Optimists are usually disappointed. Pessimists are either right or pleasantly surprised. I tend to be a disappointed pessimist.

View Raymond's profile

Raymond

675 posts in 2364 days


#3 posted 1344 days ago

I think my longest run is about 15 to 20 ft. I have not noticed a problem with my HF collecter keeping up. I do have my jointer and thickness planner close to the DC within about 6 feet. The one the at the end of the long run is my table saw.

-- Ray

View Canadian Woodworks's profile

Canadian Woodworks

609 posts in 1707 days


#4 posted 1344 days ago

I used a similar but 3hp from busy bee, I added a cyclone from oneide and now don’t even use the bag filters but I blow my air outside.

I use 6’’ ducting that you would use for home heating, I had my buddy hvac guy put it all up, it was cheap, quick and I pump lot’s of dust through it every day. I’m glad I went with the 6’’ over 4’’!

The dust collector had a thing that went to 3 4’’ hoses when I bought it, but that did not last long.

Outside the window is where the motor/fan is so it’s nice and quiet in my shop, the loudest noise from the dust collection is the dust swirling around in the barrel. To give you an example we empty the 30gal pail a fwe times a week easy. So we put a lot of dust through this.


-- Paul Lemiski, Ontario Canada, Custom Wooden Rocking chairs and tables http://www.canadianwoodworks.com

View George M's profile

George M

117 posts in 1401 days


#5 posted 1344 days ago

I have mine set up with permanent 4” lines. The longest run is about 25 feet and contains no 90’s – used all double 45s.
Also I use the Thien cyclone seperator and vent it directly to the exterior rather than to the filter. I find it does an OK job. When I built the system I was unsure if it would have enough power to do a great job, so I built the mounting to accomidate two of them with the intentions of adding another blower assembly to it (still have another coupon for $139 good until 2/12/11). Not sure yet if I need to or not.

-- George, Parker Colorado

View live4ever's profile

live4ever

983 posts in 1647 days


#6 posted 1344 days ago

Hi George,

Thanks for the info!

What tool is at the end of your longest run? Do you feel you’re getting enough cfm at that tool?

-- Optimists are usually disappointed. Pessimists are either right or pleasantly surprised. I tend to be a disappointed pessimist.

View Lee Barker's profile

Lee Barker

2163 posts in 1487 days


#7 posted 1344 days ago

I scanned the posts and didn’t see any mention of a copper ground wire if you’re using PVC. Absolutely a must. Put it in the planning.

Also, a great way to seal joints is with 3” cold shrink wrap. No duct tape residue, easy to undo if you need to unplug the line, easy to reseal.

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View brtech's profile

brtech

664 posts in 1559 days


#8 posted 1344 days ago

Ya know, there is a difference of opinion out there on the necessity of grounding PVC. Lots of folks don’t bother and report no static problems. Also there are several knowledgeable folks who say that running a ground wire inside the pipe won’t actually drain the static charge, and what would be needed is a conductive surface and not a wire.

View Lee Barker's profile

Lee Barker

2163 posts in 1487 days


#9 posted 1344 days ago

Thanks for that info, brtech. I am going by my experience here, which may not be good or universal science. I had had PVC in a prior location, and when I moved into my 1800 sq. ft. shop I had more runs and lengths. Not a lot, but more. I became aware of a snapping sound periodically as I was running the system, and it was a visible spark. Grounding the system stopped that. Hence my vehemence, but this could be an isolated instance and I accept that there could be other systems that function fine without grounding.

-- "...in his brain, which is as dry as the remainder biscuit after a voyage, he hath strange places cramm'd with observation, the which he vents in mangled forms." --Shakespeare, "As You Like It"

View live4ever's profile

live4ever

983 posts in 1647 days


#10 posted 1344 days ago

Thanks for the little tangent, fellas. :) Now and again I do hear some stories like Lee’s that make me think it can’t hurt to do the grounding, even if in most cases it’s unnecessary.

Now back to the question at hand, can anyone tell me at what static pressure drop for my branches will the HF DC fail me?

-- Optimists are usually disappointed. Pessimists are either right or pleasantly surprised. I tend to be a disappointed pessimist.

View dbhost's profile

dbhost

5378 posts in 1869 days


#11 posted 1344 days ago

FWIW, I am using a 5” main, to 2 4” branch lines. Top and bottom, so I end up with a 4” line to the top and a 4” line to the bottom of the machine. Probably not Pentz approved, but it is working out for me as far as I can tell. I really wish I had a Dylos meter to figure out what my changes do to my air quality…

I do fear though, if I had a Dylos meter, I might find myself wanting to seriously upgrade my DC to a 3HP or better cyclone, and I can not afford one yet… Key word there… Yet….

-- My workshop blog can be found at http://daves-workshop.blogspot.com

View DonH's profile

DonH

483 posts in 1454 days


#12 posted 1343 days ago

I have the 2hp collector with 5 inch main lines and 4 inch hook ups to machines. I am not happy with it and find one run of about 16 feet does not draw as well as a shop vac. I supplement the DC system at the band saw with a shop vac hose stuffed under the table next to the blade. That triples my dust collection and eliminates debris around the saw.

I am looking into changing the system

-- DonH Orleans Ontario

View crank49's profile

crank49

3380 posts in 1608 days


#13 posted 1343 days ago

It’s all relative. The HF DC can produce about 500-600 CFM at 12” static, but the higher the static, the lower the CFM. The system will find its own balance and will run at that. If you have a cyclone with a 4.5” static drop and a duct drop of 7” you are right up against the limit of this machine. I would suggest you don’t need a cyclone with a 4.5” drop to catch the big heavy stuff and for me, that’s the main reason for having a cyclone. A simple dropout box is adequate. You just want a container, trash can, with enough cross sectional area to drop the velocity of the air stream below 150 FPM, 4sq.ft., and change the direction of the flow by at least 90 degrees, 180 degrees is better, and send the air on its way..leaving the big saw dust and chips in the can and the fine dust and air continue on to the fan and filter. This system will not catch as much fine dust as a true cyclone, but it will only cost you about 1” to 2” of static loss.

A larger pipe will only find a balance at a higher CFM up to the limit of the fan and motor. There is no need to use a 6” pipe for the HF collector as you will not gain any significant capacity and only reduce the velocity of the air flow within the pipe. The cost of 6” pipe will not be justified for the minor capacity gain. Also, 5” pipe, while ideal for maximum flow is hard to find and can be expensive. As I said earlier I used a 2.5” and a 4” pipe on my system and they are both open at the same time. A 3” and a 4” would be even better, but I just used what I had available.

CFM is = the square ft. area of the pipe times the velocity of the air flow.
3” dia. = 0.04908sq.ft. X 4500 FPM = 220 CFM
4” dia. = 0.08727sq.ft. X 4500 FPM = 392 CFM (note 220 + 392 = 612 CFM, ~ the limit of the HF DC)
5” dia. = 0.13635sq.ft. X 4500 FPM = 613 CFM (also the limit of the HF DC, the size of the fan inlet)
6” dia. = 0.19635sq.ft. X 3150 FPM = 618 CFM (CFM won’t increase, the velocity will decrease)
If air flow velocity gets much below 3000 FPM you will start to have plugging problems.

By the way, the flow of a DC is in no way the same as a shop vac. A typical shop vac might produce about 120 CFM at a static pressure of over 60”. Think high pressure, low volume. This is what you need to generate high velocity to capture fast moving dust, therefore a shop vac is good for most portable tool applications where you might be working with small pipes.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

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live4ever

983 posts in 1647 days


#14 posted 1343 days ago

Thank you crank. That was very helpful. I am calculating that my longest branch will result in somewhere between 7-8” of static pressure drop. Theoretically this should be within the capabilities of the HF…according to what you’ve said, I should still be able to get 500-600 CFM at the tool on that branch.

It seems like you and Bill Pentz disagree on the pressure drop of a trashcan separator. In his calculator he figures 4.5” for a simple trashcan separator, which would probably put my system over the limit. But if a trashcan separator only results in about 1-2” of static loss, I should be ok.

As for using a 5” main, do you think it’s worth the cost/effort of finding it vs. the CFM gain? I don’t know how much 5” pipe costs, but it seems like it might be worth the hassle given the numbers you posted. I’d like to make it work with 4” since it’s easy to get and cheap but maybe that’s not a good way to go. Guess I need to figure out the cost of 5” to make a determination there.

-- Optimists are usually disappointed. Pessimists are either right or pleasantly surprised. I tend to be a disappointed pessimist.

View crank49's profile

crank49

3380 posts in 1608 days


#15 posted 1343 days ago

A sheet metal shop (HVAC folks) can make you any size pipe you want and probably no more than PVC. The expense comes in when you start making elbows, reducers, and especially wyes. I have considered using 5” diameter between my dropout box and the fan inlet and then having two inlets into the box, a 3” and a 4”. That would balance nicely and I would not have to pay for custom fabricated wyes.

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

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