3hp vs. 5hp SDG dust collector

[Alan Bienlein]

That's true. For instance, the 3 hp motor in a table saw pulls three horsepower worth of electricity only if you're cutting really hard wood with a dull blade and a really fast feed rate. Most of the time, it draws lots less power.

But the motor in a cyclone is different. The cyclone is sucking lots of air all the time. In fact, to get high cfm ratings, the cyclone manufacturers run the motor right near the rated horsepower. That is, the 3 hp motor in the cyclone is eating nearly three horsepower of electricity all the time it is running.

I have to disagree with that statement. If you were to put an amp meter on your motor to the cyclone and open all your blast gates you shouldn't be able to draw more amps than the motor is rated for. As you close blast gates the amp reading starts to drop as the motor has less work to do since you are starving it for air. On mine with all blast gates closed it draws about 10 amps. Open one and it goes to about 16 amps and with 2 open about 17.9 amps but i don't exceed the nameplate rating of the motor with all gates open otherwise you would burn up the motor.

[Mark Beall]

That's true. For instance, the 3 hp motor in a table saw pulls three horsepower worth of electricity only if you're cutting really hard wood with a dull blade and a really fast feed rate. Most of the time, it draws lots less power.

But the motor in a cyclone is different. The cyclone is sucking lots of air all the time. In fact, to get high cfm ratings, the cyclone manufacturers run the motor right near the rated horsepower. That is, the 3 hp motor in the cyclone is eating nearly three horsepower of electricity all the time it is running.

Yea, you're right. I wrote that without thinking too much about it.

Thanks for the answers. I'm glad I asked the question since I really hadn't considered the heat issue. Since a good part of this project is to ensure that the workshop area is pretty well sealed off from the house, tapping into the HVAC system to get some AC down there wouldn't be very consistent with that plan.

The 3 hp unit will do what I want and will cook me less quickly

Thanks,
mark

[Mark Beall]

Mark, I noticed this is your first post. Welcome to the Creek

I have a 3HP Oneida, Commercial unit in a 750 sf shop (28 X 28). I have an 8" main line and all 6" runs. The 3 HP unit does a great job. I am a one man shop, so most of the time I only have one gate open at a time. However, sometimes I have several open and does not seem to make a difference.

One thing to think about.. You did not say how much power you have in your shop. I have a 100 amp sub panel in my shop. You need to be able to run several things at a time. I run my 3 HP Oreida, My 5 HP table saw, and my 5 HP air compressor may pop on, and my air conditioner may be running. I have enough power to handle all.

The Oneida 3 HP does a great job, Sam

Thanks for the welcome, Sam

One of the first things I did when I moved in the house was run a 100 amp sub panel to the area I was going to set up my shop, mainly since they only left me 2 open breaker slots in a 200 amp 40-slot main panel

I'm pretty much setting up the DC system as you described, I'm skipping the 8 inch main line since it pretty much has to split into two runs right at the collector. Since the only two combinations of tools I'm likely to run at the same time are either my jointer and either table saw or planer this should work out well since the jointer is on one run and the table saw and planer are on the other (and they are only 8 and 10 feet from the DC anyhow - yes it may be a little noisy that close to the table saw, but there is room to enclose it if I need to).

mark

[Mark Beall]

I have to disagree with that statement. If you were to put an amp meter on your motor to the cyclone and open all your blast gates you shouldn't be able to draw more amps than the motor is rated for. As you close blast gates the amp reading starts to drop as the motor has less work to do since you are starving it for air. On mine with all blast gates closed it draws about 10 amps. Open one and it goes to about 16 amps and with 2 open about 17.9 amps but i don't exceed the nameplate rating of the motor with all gates open otherwise you would burn up the motor.

From what I read, you're both right (did a little searching after his post). A DC will draw minimum power when it's not moving any air (all gates closed) - unfortunately they aren't of much use in that configuration . A well designed system will draw close to it's max power over a good part of the fan curve with that dropping off at the highest static pressures (since it's not moving much air at that point) - note that it's max power might not relate to the hp of the motor, putting in a 5 hp motor in a DC properly designed for a 3 hp one shouldn't really change anything - you need a bigger impeller to move more air. Upshot of it is that, barring a bad design of the DC or having very restrictive duct work, you should be drawing close to rated power in normal use.

Of course someone who knows more than I learned searching on the internet may well correct me

mark

[Bas Pluim]

Let me say that I just purchased it - the duct work arrives today and the cyclone comes tomorrow. I do not know how well it works.

Once you've had a chance to set things up, I'd be interested to hear how you like it.

[Philip Rodriquez]

Once you've had a chance to set things up, I'd be interested to hear how you like it.

I think I will post a review, with pictures, once I get it installed. Because I park two cars in the garage, I only went with 5 drops. 4 drops are for my stationary equipment and the 5th will service my mobile tools. I received the duct work, yesterday, and I'm receiving the cyclone today. I'll have everything up and running by Sunday. I'm upgrading from a Jet 1100 canister unit.

Like I said, I was completely surprised when they recommended the v-3000. The key was that I only run one tool at a time. and that my runs (3 branches) are less than 20 feet. The specs indicate that the cyclone will service one "6, one 5", or two 4" ports at a time.

The V-3000 W/ ductwork was about $1,000 less than the 3 H.P. SDG setup would have been - which I gladly would have purchased if Oneida said it was necessary.

[Sean Nagle]

Phil, I'm surprised they didn't try to upsell you because of our elevation. That's how I ended up with a 2.5HP SDG instead of the 2HP. By the way I live in Colorado too. I'll update my profile.

[Philip Rodriquez]

Phil, I'm surprised they didn't try to upsell you because of our elevation. That's how I ended up with a 2.5HP SDG instead of the 2HP. By the way I live in Colorado too. I'll update my profile.

Me too. I was very specific (since further upgrades can cost thousands more) and Crystal assured me that the V-3000 was all that was necessary. Honestly, I would not have batted-an-eye if she had told me to buy the 3 H.P. model. Heck, who am I to argue.

$2,200 vs $3,500ish... is a great savings! The big test will be to see how well it does with my table saw. My jet does a good job, with the addition of the BG, but I've always wanted to add more cfm for the below-the-cabinet collection.

[Sean Nagle]

Good luck with your new system. Let us know how it works.

[Matt Armstrong]

I bought the 3hp SDG after consulting with Oneida. My duct system is based on Oneida's recommended design for my shop and doesn't require any more than 5" and 4" duct at the machines. Basically, there's an 8-7-7 wye at the intake of the DC with 7" duct only as far as the first drops. Six inch duct goes around the perimeter to other drops that are 5" and 4". Unless you're using industrial sized machines, smaller duct will work great and save some money.

Agree or disagree with Pentz' research, but the math does not work out very well for 4" ducting.