too much for the motor?

[David Miller]

Hi all,

I'm am nearing the completion of my Bill Pentz design cyclone. I am using the Sheldon Eng. 14" impeller and a 2hp Delta motor. I fired the thing up tonight and I am pulling 11.7 amps on both legs of the 220 circuit. The motor is rated at 10 amps on the label. I reduced the inlet size by half but it had no effect.

So how conservative are the motor specs? Do you think I can get by running it at 11.7 amps? I don't have any ductwork attached so I think this will be the most it will ever pull.

Thanks,
Dave

[David Miller]

Well, I went over to Bill's website and found that I shouldn't be pulling more than 95% of the motor's rated amperage. So I guess I need to do some work.

Anyone have any idea why the draw by the motor didn't seem to decrease when I stopped down the inlet? I'd like to use this motor for now. I plan to hook it to each machine as I need it so I won't have long duct runs.

Thanks,
Dave

[Stephen Dixon]

I know it is not a good idea to run your motor with a high amp load, but I would be very surprised if the amp load didn't come down as you put your system together. Like you said, the no piping test represents the most air your fan will ever see, and once the system is together it will be much lower. I would be happy with 10% overamps in that situation knowing that once the system is complete my air flow will still be up near full load. BTW I have worked with many dust collectors, and amps is almost directly related to air flow
Steve

[Jim Becker]

Any chance that's too small a motor for the blower? I believe that Bill specs 3-5hp for the system design...

[David Miller]

Thanks for the replies. Actually, there is a section on Bill's site that lists a budget cyclone that utilizes the sheldon impeller and 2hp motor, although he does recommend the 5hp Leeson. I've ordered 10' of 6" flex hose and will test the system with it connected. I may also piece together some 6" PVC to see how it works with some ductwork attached.

In the end, if I can't get the amps down I'll go ahead and get the Leeson.

-Dave

[Norman Hitt]

Well, I went over to Bill's website and found that I shouldn't be pulling more than 95% of the motor's rated amperage. So I guess I need to do some work.

Anyone have any idea why the draw by the motor didn't seem to decrease when I stopped down the inlet?

Thanks,
Dave

One of Two Possibilities, in my mind.

First, is the Question Jim Asked about motor sizing for That 14" impeller.
Second, is the possibility of a leak in the cyclone/blower itself.

"For curiosity", try closing up the inlet completely and measure each leg's amps, which should be the LOWEST amp readings you will ever get. If this reading is not significantly below the 9.5 amps/leg (95% of max amperage rating), then the motor is definitely too small for that unit, and you WILL burn out the motor.

Let us know the results, please.

[Scott Parks]

Sheldon's has three different impellers available. Their "airfoil" impeller is specifically designed for a 2 hp motor. Their 14" material movement impeller needs a minimum of 3hp, thus the more expensive 5hp rated (really 3hp) Leeson motor.... $$$

[David Miller]

I also forgot to mention that I do not have the filter package installed yet so there is no backflow resistance. I'm sure this will reduce the strain on the motor. I'll post the results of my tests tonight.

Here is where I saw the info for the 2HP + 14" impeller:
http://billpentz.com/woodworking/cyclone/BudgetDC.cfm

Please note that Bill does recommend the 5HP Leeson motor over the 2HP, but says one 'might' be able to get by with the 2HP.

Also, I want to make it clear that I am in no way unhappy with Bill's site or information. The cyclone has turned out great because of Bill's attention to detail and his commitment to the woodworking community. Thanks Bill!

-Dave

[Bob Johnson2]

Would not reducing the air flow, either on the input or by backpressure give you more of an amperage draw? seems like it would work harder if the flow is restricted and run easier if it has no resistance.

[Jim Becker]

Would not reducing the air flow, either on the input or by backpressure give you more of an amperage draw? seems like it would work harder if the flow is restricted and run easier if it has no resistance.
Actually just the opposite, Bob. The motor is working the least when the gates are closed! Strangely enough...

[Allan Johanson]

Depending on your filters, testing them when new may not drop your airflow much at all. I tried an experiment with stuffing the 8" blower outlet into a single Farr filter and sealed the connection. I only saw a drop of 14 cfm. Yes, 14. You can't measure that with an ammeter.

Add on more ducting before you run the motor again. Running it over 11 amps for more than a few seconds will damage the motor a little bit each time you do it.

Be sure to check for leaks too. Make sure your dust bin has been sealed 100%. This may explain your lack of amp draw changes when you covered the inlet. You *did* have a dust bin in place, right? Leaving the cone completely open is a great source of air for the cyclone.

Good luck!

Allan

[Rob Russell]

Would not reducing the air flow, either on the input or by backpressure give you more of an amperage draw? seems like it would work harder if the flow is restricted and run easier if it has no resistance.

The amperage of a squirrel cage blower such as these goes up as it moves more air. Throttling back the amount of air moved, either by restricting the intake or creating back pressure on the output side, will effectively reduce the current draw. There is a high startup demand as the impeller is spinning up (the motor is overcoming the inertia of the impeller mass), but once at speed - air volume regulates current.

[David Miller]

I closed up the inlet and checked that I had the bottom of the cone closed (I did) and I fired it up. The was still some air movement out the outlet but I assume that it was just air being stirred up by the impeller (it was way too much for any of the small leaks that I have). The draw dropped to 9.2 amps. :( Not low enough to prevent the motor from going 'poof!'. So I guess I'm going to have to invest in a new motor.

Anything I could be missing? If not, anyone need a 2HP Delta motor? :)

Also, I noticed the the impeller doesn't spin 'flat'. It seems to wobble. Can I adjust this out with the three cap screws that compress the impeller onto the motor shaft?

-Dave

[Bill Turpin]

The amp draw of most water pumps and fans is reduced by restricting the outlet, not the inlet. This is contrary to home brewed engineering but it is true. There are special impellers that can make this statement un-true, but it is generally correct.

Bill in WNC mountains

[Terre Hooks]

I fired the thing up tonight and I am pulling 11.7 amps on both legs of the 220 circuit.



Exactly how did you measure this?

[David Miller]

Hi Terre,

I'm using a clamp amp meter to check the draw. Both legs are reading the same amperage.

-Dave

[Terre Hooks]

If this 'test' was without duct connected, the motor was working as hard as it will ever work.

Amperage draw will go down as static pressure is increased on a vacuum system.