Small Shop DC - 2hp vs. 3hp for piped system?

[Steve Hepditch]

Title says it all
(but here's more)

I'm in a 16x24 shop and planning to run 6" PVC to stationary tools. Blast gates, only one tool in use at a time. Longest run is approx. 30' with minimal flex and bends. Using the Pentz calculator I've got 8" (ish) SP loss over my longest run - 4x 90-degree bends, 18" flex hose, 6" pipe the whole run. Will upgrade hoods and ports no matter what DC I get.

I'm putting the DC unit in a shed attached to the shop and I'm venting directly outside (so my SP should be slightly higher than expected). I'm also building a Thien separator to put out there which will do my chip separation but add somewhere around 4.5" SP loss to my system.

I'm looking at the two popular Grizzly DC's - the 2hp G1029Z2 - http://www.grizzly.com/products/G1029Z2

and the 3hp G1030Z2 - http://www.grizzly.com/products/G1030Z2

Both seem like quality units that get good reviews. I think what I'm looking at will be solid chip collection with the 2hp unit (rated 1550 CFM with 11" SP) but an upgrade to "medical dust collection" with the 3hp blower (rated 2300 CFM with 16.7" SP).

In the grand scheme of things, the $126 difference in price is probably trivial - I'm going to spend more on ducting than on the DC itself - but I'm wondering if I have the concept correct with the 2hp vs. 3hp. Is the 2hp all I need or should I just go ahead and get the 3hp so I don't want to upgrade in the future?

As I write this it seems silly that I'm over-thinking a $125 upgrade, but I wanted some opinions as to the necessity of upgrading to the 3hp. I'm sure I can find another place to "invest" the savings if the 2hp unit will be plenty to ensure I'm getting quality (fine) dust collection...

Thanks,
Steve

[Philip Rodriquez]

I think you already know the answer... but I'll give it to you. Get the 3HP. DC can always use more HP. For reference, I have an oneida 3hp cyclone.

[Rod Sheridan]

Hi Steve, I have a few comments

1) If you are venting outside you don't need improved filtration, and it will add to your static pressure loss.

2) If you have an 8" SP loss and you add 4.5" for a separator, you're going to be at 12.5" plus another 1 to 2 inches depending upon your make up air design. Since you don't have a fan curve for either machine, how do you know that they will be able to deliver the air flow you need?

You have very high SP figures.

To put it in perspective I have an Oneida cyclone which has a fan curve that shows 700 CFM at 4" SP, 261 CFM at 8" SP which is as far as the curve goes.

In my shop my duct design actually decreases the CFM to 600 at 4" SP. (I have very short duct runs, under 10 feet).

3) For a 3HP motor, it has high input current (18 amperes). This indicates a low efficiency, low power factor motor. A premium motor would be under 13 amperes for 3 HP. I don't expect however that this is any different than any other motor at that price point.

If I were you, I'd be re-checking my SP calculations, and looking for a fan curve.............regards, Rod.

[Prashun Patel]

"In the grand scheme of things, the $126 difference in price is probably trivial... "

There is no necessity - only nice-to-have. Since the financial dif is trivial, go with nice-to-have. It might also allow you to be a little more creative about yr ducting.

I've never regretted going bigger and better with any of the tools in my shop.

The DC will be used in virtually EVERY power operation, so it's not like you'll see it sitting on yr shelf and kick yrself for getting that really odd (but cool) plane.

[Neil Brooks]

I tend to agree: the easy answer is the bigger DC.

But Rod's -- IMHO -- MUCH closer to the *right* answer.

There's some science to this, and ... for MY money ... that's where I'd start.

Like this:

http://www.airhand.com/designing.aspx

Why guess, when you can know ?

Good luck !

[Michael N Taylor]

I purchased the shop fox 1808 2 hp from Grizzly when they had them on sale and it does and excellent job. The unit is well made witha 14.5" impeller, no vibration and has plenty of suction. I have a shop very similar to yours.

[Steve Hepditch]

Rod,
My ~8" SP loss calculation already factored in the 4.5" for the separator. I think I just needed someone to jump in and tell me to man up and get the 3hp. It was my leaning anyway, just wanted to make sure it wasn't going to be more money for no better collection...

Steve

[Van Huskey]

Get the 3hp, it is a NO BRAINER. Since you are venting outside sell off the bags, yeah they are only 2.5 micron but someone will want them and with 4 bags you should be able to get a little of your money back.