mild gloat and question

[david brum]

I decided to upgrade my DC to from a 1.5hp with Thien baffle and Wynn filter to a 3 hp double bag unit with two Thien baffles and two Wynn filters. I found a 3HP DC on Craigslist for $75. It even came with an extra 3hp motor and blower unit, as well as an extra bag ring. It needs paint, but I'm not complaining.

I began to think of all kinds of ways to set up the blower/motor to conserve space and get better separation. I figured that since these 3 hp units are rated around 2000-2300 cfm and around 16" pressure, they must have a huge impeller. I could even rig this into a cyclone at some point in the future.

Well, turns out that these 3hp units have around 12-12 3/4" impellers, roughly the same size as a 2hp DC (according the grizzly site). Given the same size impeller then, how do these nearly double the cfm? They do have double the filter area. If that's the answer, why can't you just double the filter surface area an a 2 hp DC. Would the fan speed burn up the motor? I'm really curious about this.

[Lee Schierer]

Check the motor RPM closely. The 3 Hp is likely a 3450 rpm motor while the 1.5 Hp is a 1750 RPM. Twice the speed twice the air flow, but you need more HP to move it that fast.

[david brum]

That makes more sense Lee. Thanks. I did take a look at the rpm and it is indeed 3450. I also noticed that the individual fan blades seem deeper, so perhaps some volume is gained there as well.

That opens up more possibilities, for sure.

[Mike Cruz]

It has been explained to me that there is no way that a 12 (mine) or even a 12.75 (yours) inch impellor is going to get you 2300 cfm. Ratings are ratings, not made in the real world. That said, I've wondered the same thing about how the 2 hp model at 3450 rpm and 6" inlet creates 1550 cfm, and the 3 hp model with the same impellor and same rpm and 6" inlet creates 2300 cfm. Either way, you got an upgrade...well at least you SAY you got an upgrade. Without pictures, I don't believe it... :rolleyes:

[david brum]

Thanks for the input Mike. I think there's something fishy in dust collector town. I emailed Grizzly to ask how they accomplished so much more cfm with the same size impellers. The response I got was that the 7" inlet allowed much more airflow, thus requiring the bigger motor.

This doesn't make complete sense, since the blowers both have the same outlet size.

You're are right that it should be an upgrade, although I don't know for sure. I took the cover off the blower and measured a 12" impeller. I know that it should give more cfm than my current 11" impeller. I hope it does. I'm hesitant to start on this project because I'm not sure if I'll get much gain for the effort and expense involved.

Right now, the DC is in parts in a corner of the shop. I will certainly post a picture when I get it set up.

Thanks!

[Mike Cruz]

David, I'm sure you will get more cfm out of this unit than your 1.5, a lot more. The question is how much more... Will it be 2300 cfm, doubtful, but you will probably be able to pull high teens. Just my guess. I would definatly hook 'er up. I noticed more with the upgrade from the 2 hp unit to the 3 hp unit. The question there is, did my 2 hp unit really pull the 1550 claimed? So, even if I am at mid to high teens now, I was probably at low teens before...so the upgrade is worth it...to me at least. Now I know I can take advantage of 6" piping.

[david brum]

Thanks Mike, that's reassuring. I'm gonna do it. I'll be very pleased if I get anything over 1500cfm.

Best wishes

[Mike Cruz]

Uh, what was I thinking... It'll never work. You see, where you are there is a difference in pressure, temp and humidity. With the spin of the earth and Pacific winds, you'll need a completely different system. Well, since you won't be needing all that junk you picked up, I'll be happy to take it off your hands. I'll even give you more than you paid! What do you say to $100? I'll even pay for the shipping...

Hey, I thought I had a bit of a gloat on my hands when I picked up the Grizzly G1030 with bags (no canister filters) for $200. I was tickled pink. It is a 1997 model, but had clearly been almost not used. You got a steal!

[david brum]

You should have seen what I had to do to get this thing! I drove out to a guy's farm and hauled it out of his barn. He had it as part of a '90s era Oneida cyclone which used a bank of skinny felt bags coming out of a square plenum. I had to remove about 30 rusty bolts in order to get it into my truck. Luckily, he let me leave the plenum,etc behind. I also left a huge box of metal 4" ducting and fittings.

He also had a cylone body which might have been a great score if it hadn't been hopelessly outdated.

Good fun. I'll post pictures!