Piggy back DC's

[Dave Schmittou]

Hi
This is my first post on this site although I've been lurking and learning for a while now, I hope my first question isn't a flat out dumb one. I need to upgrade my dust collection, I have a 2hp unit from Grizzly that just isn't doing the job (mainly chips from a 18" planer) I just saw Harbor Freight has a 2hp unit thats the same as mine on sale for $140 and the thought hit me that I may be able to put the two together and hopefully solve my problem. I'm not expecting a 200% increase in collection but I think 150% would solve my problem. also in the plans is a cyclone. Bottom line I would save a lot of money if this would work (more tools).
Thanks for any input.
Dave

[Dan Hintz]

I see issues with this as the more powerful blower is going to try and steal some air from the less powerful unit, reducing the efficiency of the larger unit in the process... if it's extreme enough, that can cause clogging in certain tubes, and that's never a good thing. I would suggest using them as separate units and not tying them together.

[david brum]

Hi Dave

Before you buy another DC, it's good to ask what size DC hose you're using. For instance if you're only using 4" hose or ducting, you're only getting half of the available airflow.

If you're already there, this seems like it might work better for you:
http://www.harborfreight.com/3-hp-du...tor-98872.html

It's currently on sale for $299 according to the flyer I got yesterday.

[Dave Schmittou]

Thanks for the quick replies. They both make a lot of sense. I could buy the larger unit, off mine on craigs list and have the same out of pocket. Now for the duct size issue, I just (6 months ago) completed the system and ran 4" duct around the entire shop with a takeoff across the ceiling to the center of the room installed take offs for every stationary power tool that generates dust/shavings, a total of nine drops some of them splitting at the tools with a Y to serve two tools, all with its own 4" shutoff. How much of this new ducting do I need to tear out and replace with 6" ducting? Would it be just the main trunk?
Wish I'd found this site first.
Thanks again - you guys saved me a lot of time, money and frustration.

Dave

[Dan Friedrichs]

How much of this new ducting do I need to tear out and replace with 6" ducting? Would it be just the main trunk?

If you're only using one machine at a time, it's not helpful to up-size the main trunk. Essentially, the smallest diameter anywhere in the run determines (more or less) the total airflow for that run. So a 6" main trunk, reducing to 5" flex duct, reducing to 4" port at the tool, will move about the same amount of air as if you had just run 4" duct all the way.

Have you read Bill Pentz's website? It will take you a good day to read through everything, but once you're done, you'll know everthing you need to know about dust collection.

That said, some people have a tendency to over-design DC systems. If you are happy with the performance you get with your 4" duct system, it is probably not worthwhile to replace it (on the other hand, if you're unhappy that the system performance - ie, too much dust left uncollected - then upgrading the ductwork to 6" would probably make significantly more impact than upgrading the dust collector, itself)

[Alan Lightstone]

We've had this discussion before. I still haven't decided if I'm going to try it.

Here's a link regarding the previous discussion:

http://www.sawmillcreek.org/showthread.php?t=136395

The upshot was series = good, parallel = bad. I was thinking that two piggyback HF DCs would be cheaper than a higher HP DC.