Dust Collector trunk and branch questions

[Zane Harris]

Pondering questions, building up to the eventual install of a dust collection system in a small (VERY small) one man shop, weekend warrior type...

#1) Can the Harbor Freight 2HP collector (97869)be modified to have a 6" rather than a 4" inlet?

#2) My logic center tells me that if I am running two ports simultaneously off of a machine, such as an overhead blade guard and an under machine port on a table saw, that the sum of the cross-sectional area of the two branches should be as close as possible to the cross-sectional area of the main trunk. Such as, if I have a main trunk of 6", with a cross-section area 28.27 square inches, that my best bet combination for the two branches would be 5" for the main saw port, and 3" for the overhead blade guard, (19.63 + 7.07 sq. in., putting me within 1.57 sq. in. of the same as the trunk). Am I right in this logic?

#3) Again, my logic center is telling me that in the scenario described in #2 above, that I should reduce my branch diameters at the wye, and not try to run full trunk diameter as far as possible, in order to keep the particulate in air suspension while they are approaching the main duct. Again, is my logic correct?

#4) Regarding blast gates, it seems that most blast gates are installed conveniently close to the tool they are servicing. While this may be convenient, would the dust collection system work more efficiently if the blast gate were installed as close as possible to the wye branching off to that tool, so that the dust collector does not have the added burden of maintaining suction in an air space that is not being used?

If these are stupid questions, please be kind...

[Art Mann]

I don't see any benefit to modifying the dust collector so it uses 6 inch pipe. At that diameter, the velocity of the air will be too low to keep the waste suspended and you will have to deal with material settling in the pipe.

If there are no leaks in your branch pipe, then it doesn't make any difference where the blast gate is located. The only time additional energy is used in the larger volume of a longer pipe is during the first seconds of startup when the collector is pulling a vacuum in the whole system. No work is being done (energy consumed) unless the air is moving.

[Ryan Mooney]

Pondering questions, building up to the eventual install of a dust collection system in a small (VERY small) one man shop, weekend warrior type...

#1) Can the Harbor Freight 2HP collector (97869)be modified to have a 6" rather than a 4" inlet?
[/QUOTE}

Yes but I wouldn't. In my experiments trying to increase the pipe size past 5" dropped the airflow low enough that it started leaving chunks in the pipe.. of course that was with flex pipe and I had some other restrictions in the flow so YMMV. At 5" (the size at the inlet before the stock Y) it was pretty happy.. but I also realize that 5" is a hard size to find.

[QUOTE=Zane Harris;2167457]
#2) My logic center tells me that if I am running two ports simultaneously off of a machine, such as an overhead blade guard and an under machine port on a table saw, that the sum of the cross-sectional area of the two branches should be as close as possible to the cross-sectional area of the main trunk. Such as, if I have a main trunk of 6", with a cross-section area 28.27 square inches, that my best bet combination for the two branches would be 5" for the main saw port, and 3" for the overhead blade guard, (19.63 + 7.07 sq. in., putting me within 1.57 sq. in. of the same as the trunk). Am I right in this logic?


Yep. You can get away with a bit of fudge around that as long as there is adequate airflow...



#3) Again, my logic center is telling me that in the scenario described in #2 above, that I should reduce my branch diameters at the wye, and not try to run full trunk diameter as far as possible, in order to keep the particulate in air suspension while they are approaching the main duct. Again, is my logic correct?


Nope. There is more friction on a smaller pipe so you're better off keeping the pipe as large as possible as long as possible (given adequate airflow, optimizing for fewest bends, etc...). Assuming the larger pipe isn't TO much larger then the airflow should stay high enough..



#4) Regarding blast gates, it seems that most blast gates are installed conveniently close to the tool they are servicing. While this may be convenient, would the dust collection system work more efficiently if the blast gate were installed as close as possible to the wye branching off to that tool, so that the dust collector does not have the added burden of maintaining suction in an air space that is not being used?


Well assuming that there are no leaks.. the cost of the suction on the extra pipe ends up being effectively nothing in theory.. In practice pipe joins often have some leaks, so it might well make sense.

[Wade Lippman]

You are seriously over-analyzing this.
It doesn't make any difference where the blast gates are. I put them where they are most convenient.
Running 4" to your saw and then 4" to the cabinet and the guard is fine. May not be optimal, but it is unlikely to be the worse problem you have.
"Maintaining suction" is not an issue. This is not a vacuum cleaner, it is a dust collector; air movement is all that matters.
If HF put a 4" port on it, it is an admission that the machine will not support anything bigger. At least that is what it is supposed to mean.

[Robert Delhommer Sr]

The HF 2HP DC actually has a 5" inlet, take the "Y" off and you have a 5" inlet. I don't see why you could not adapt to a 6' if you wanted. :)

[Jim Andrew]

Has anyone actually tested the capacity of the HF dust collector? Be nice to know if you are installing a system.

[David L Morse]

Has anyone actually tested the capacity of the HF dust collector? Be nice to know if you are installing a system.
Here's what I measured:
273075

[Ole Anderson]

5" to the bottom of your TS and 3" to the blade guard is a common solution and in fact mentioned by Pentz. As to when to change pipe sizes, it depends if the run is horizontal or vertical. In the case of your 3" drop to the saw, I have no problem going to 4" or even 5" once the run becomes horizontal. You really need to keep your velocity up in the vertical runs. I run a 5" out of the bottom of my TS, then it wyes into a 6" (coming from my MS) and goes vertical. Once in a great while I need to open up the vertical bend and remove an offcut, or the container of pencils that got sucked up when they spilled into my MS hood. And keep in mind that you need about 800 cfm to your TS, and figure about 8" of suction losses. If you look at the fan curve in the previous post, you will see that the HF 2 hp unit (actually less than 2 hp as it is really difficult to get a 2 hp motor to run on 115 volts) will be less than marginal in providing proper fine dust collection at your TS. But it is certainly better than a shop vac or nothing. Some true cyclones will get 800 cfm at 8" sp with 2 hp. Mine does.

[Zane Harris]

Is it possible to rewire the HF DC for 230-V?

[Michael W. Clark]

Zane,
I would say you are on the right track for all 4 points above.

Stay 5" or less according to David's curves. Metal snap lock duct is commonly available in 5" diameter.
Mike

[Art Mann]

Is it possible to rewire the HF DC for 230-V?

It may be possible but will not typically do much good. The horsepower rating of a motor does not change with voltage. The only benefit to running a motor at 240V rather than 120V is that it requires half the current to run at maximum power. There are voltage drops (and power losses) associated with the current passing through the resistance in the wiring feeding the dust collector. If this resistance is large enough to be a significant factor in the dust collector power output, then you have a wiring problem, not a voltage problem.

[Ryan Mooney]

Is it possible to rewire the HF DC for 230-V?

No, its a 110v only motor.

[Jeff Duncan]

If your planning on buying additional equipment, (or already have it but haven't mentioned it), I recommend going with a 6" main. Of course you can always make do with less, but for the few extra dollars for a slightly larger dust collector, you'll leave yourself some room to grow. A Grizzly 2 HP collector comes with a 6" intake and has a good amount of air flow for the price. If your going to stick to smaller tools then I'd stick with the 5" size to match the port. Running ducting larger than the DC port doesn't make much sense to me as your not likely going to move enough air. Running smaller like 4" doesn't make sense either as your choking the system and basically wasting some of your collectors capacity.

I also agree on positioning of the blast gates, put them where they are most easily accessed, there's no gain moving them farther away. And run your main duct as far as you can before branching out.

good luck,
JeffD

[Zane Harris]

Okay, now I am looking at the Grizzly G0548ZP, which is a nice compromise between the price of the Harbor Freight unit, and the features of the Jet DC1200.


If your planning on buying additional equipment, (or already have it but haven't mentioned it), I recommend going with a 6" main. Of course you can always make do with less, but for the few extra dollars for a slightly larger dust collector, you'll leave yourself some room to grow. A Grizzly 2 HP collector comes with a 6" intake and has a good amount of air flow for the price. If your going to stick to smaller tools then I'd stick with the 5" size to match the port. Running ducting larger than the DC port doesn't make much sense to me as your not likely going to move enough air. Running smaller like 4" doesn't make sense either as your choking the system and basically wasting some of your collectors capacity.

I also agree on positioning of the blast gates, put them where they are most easily accessed, there's no gain moving them farther away. And run your main duct as far as you can before branching out.

good luck,
JeffD

[Allen Holz]

I believe the Grizzly is a better bet. You won't be disappointed with the few extra dollars you spent.

Allen

[james glenn]

I have this dust collector installed, modified to 6" mains and branches where possible (in the event I ever upgrade, but doubtful), then branch to 4" mostly and a few even smaller depending on the machine it hooks to (I have a drop for the router and such). I have more bends and runs than you can think, as I have a basement shop, and with the Thein separator it still pulls the dust and solids to the canister. Granted I may not get every last bit of fine dust, but then again I don't' even turn it on for a one time cut. I also use a box fan with furnace filter to collect fine dust and any non wood dust I kick up down there.