dust collection hp and duct size?

[keith ouellette]

As many now know I need a new dc. I think I am now going to get a 2hp 1500cfm dc from penn state.

My question is:

Seeing I only have 4" duct is the extra cfm going to be waisted due to the 4" pipe or will it help?

MY motor/fan/shroud is on a shelf at the top of an outside room at the back of the shop and the 4" duct runs at the ceiling and down to the machines. The longest a run could be is about 20' with the drop to a machine.

[David Freed]

As many now know I need a new dc. I think I am now going to get a 2hp 1500cfm dc from penn state.

My question is:

Seeing I only have 4" duct is the extra cfm going to be wasted due to the 4" pipe or will it help?

Running a single 4" duct will restrict, but not damage the collector. Can you run either a second 4" or switch to a 6" duct into your shop?

[keith ouellette]

Running a single 4" duct will restrict, but not damage the collector. Can you run either a second 4" or switch to a 6" duct into your shop?

Funny you mentioned running a second 4". I used 4" thin wall pvc for the duct and have about 40 or 50 ft lying out back. Of course I would love to upgrade to 6" but I don't really even have the money for the new dc (believe it or not my wife told me to use he valentines day present money for my dust collector. she's one in a million)

with the 2hp dust collector could I run 2 4" pipe to things like the table saw and the planer and get the same result as if I used 6" pipe?

[Jason Beam]

Kinda .. not quite, though. 6" pipe is more than double the area of two 4" pipes, but you'll certainly do better than a single 4" ... There was a thread on here once discussing something very similar to this. The conclusion was it wasn't a great solution but it was undoubtedly an improvement over a single 4" line.

[keith ouellette]

but back to my origional question.

if I do nothing else other than increase the hp from 1 1/2 to 2 will there be an improvement?

[Jason Beam]

it's hard to answer that question ...

Yes - IF your previous dust collector was not able to move all the air it possibly could through that 4" duct. If the impeller design was poor and it suffered from a lot of drag, increasing just the HP will help. But you're replacing the whole thing, so this doesn't really apply.

Yes - IF your previous dust collector had trouble pulling full flow through the 4" pipe and your new one does not. It should be noted that you can't trust what the company says it will pull - A 2hp is not likely to be able to pull 1500cfm, not under any kind of SP anyway, I don't think.

No - If your previous dust collector had no problem pulling maximum flow through 4" pipe.

No - If the new one has a poorly designed impeller that isn't as efficient as your old one.

It can be tricky to judge improvement, too, once you factor in that your old DC likely had a good cake of dust in the filter media (bags, canister, what have you) that reduced it's flow. The new one will look like it's miles above the last one, but will gradually build up that same cake and slowly degrade as well.

There are just too many variables to say one way or the other. I would venture to guess you won't see an improvement - or much of one, anyway, with the added half horse. But there are WAY too many variables to be certain.

[David Freed]

With the 2hp dust collector could I run 2 4" pipe to things like the table saw and the planer and get the same result as if I used 6" pipe?

Kinda .. not quite, though. 6" pipe is more than double the area of two 4" pipes, but you'll certainly do better than a single 4" ... There was a thread on here once discussing something very similar to this. The conclusion was it wasn't a great solution but it was undoubtedly an improvement over a single 4" line.

I agree. A 6" pipe has 13% more capacity with 25% less surface area to create resistance.

[keith ouellette]

it's hard to answer that question ...

Yes - IF your previous dust collector was not able to move all the air it possibly could through that 4" duct. If the impeller design was poor and it suffered from a lot of drag, increasing just the HP will help. But you're replacing the whole thing, so this doesn't really apply.

Yes - IF your previous dust collector had trouble pulling full flow through the 4" pipe and your new one does not. It should be noted that you can't trust what the company says it will pull - A 2hp is not likely to be able to pull 1500cfm, not under any kind of SP anyway, I don't think.

No - If your previous dust collector had no problem pulling maximum flow through 4" pipe.

No - If the new one has a poorly designed impeller that isn't as efficient as your old one.

It can be tricky to judge improvement, too, once you factor in that your old DC likely had a good cake of dust in the filter media (bags, canister, what have you) that reduced it's flow. The new one will look like it's miles above the last one, but will gradually build up that same cake and slowly degrade as well.

There are just too many variables to say one way or the other. I would venture to guess you won't see an improvement - or much of one, anyway, with the added half horse. But there are WAY too many variables to be certain.

well that makes sense. there are a lot of un known variables.

If I extrapolate from what you have said if I stay with a 1 1/2 horse collector (rated at 1100cfm) and it is not designed as well as my last one it will be weaker. if I go with a 2hp (1500cfm) and it has a design flaw then I will probably end up with the same as what I had before. If the 2 hp has no design flaw I will still be the same. If I make an upgrade to the duct then the 2hp will help

Just in case I make an upgrade to the duct system I guess I will get the 2 hp.

[Jim Becker]

Keith, just be aware that you'll not get anything close to "1500CFM" from that DC. With 6" duct, you'll be able to get in the neighborhood of 800CFM; maybe a little more, depending on "things". (4" duct tops out at about 350CFM...that's all that can fit in the pipe at the typical velocity of the moving air) The 1500 number is not a "real life" thing and is marketing oriented.