Dust collector electrical testing (redux)

[John Lanciani]

OK, after helping to derail a thread the other day (sorry Randy), I decided to do some further testing of my dust collector to get a better handle on the relation between static pressure, airflow, and motor power output. My day job is for an electric utility and about 50% of my time is spent dealing with power quality issues so all or the test equipment needed was close at hand.

My dust collector is an Oneida V3000, and it is fitted with a US made Leeson 3hp motor. The pertinent specs off of the motor are as follows;

Full load amps – 13
Full load power factor - .91
Efficiency – 81.5%
Output – 3hp / 2.25 kW
Capacitor start / capacitor run

I used the following test equipment; UEI EM151 digital manometer, Fluke 41B power harmonics analyzer, Fluke 33 true RMS clamp on ammeter, Fluke 189 digital multimeter.

The CFM numbers are extracted from an Oneida published fan curve for the V3000. SP measurements were taken from a pitot tube at the cyclone inlet.

Horsepower was calculated using this formula; voltage (238) x current x pf x eff. / 746

The results were as follows;

SP ______CFM___ Amps___ PF___ HP
12.4 (max)_<100____7.3 ____.71 ___1.34
12 _______200_____7.5____ .73____1.42
11 _______400_____8.7 ____.81____1.87
10 _______525_____9.6 ____.83____2.07
9 ________650____10.1 ____.86____2.26
8 ________775____10.3____.86____ 2.3
7 ________900____10.6____.86____2.37
6 _______1000____10.9____.87____2.47
5 _______1100____11.1____.89____2.57
4 _______1200____11.3____.89____2.61
3.7(min) __1250____11.4____.89____2.63 (1.97kW)

One other interesting piece of information, the locked rotor / inrush peak current was 159 amps.

I’m not really sure that this information has too much value other than to illustrate the relationship between SP, CFM, and HP for a typical small shop dust collector. It did reassure me that my system as installed is working as advertised. There is a little bit of headroom on the motor so it should live a long and happy life.

[james glenn]

So if I am reading this correctly, it confirms what was was said before by some.

The less air (cfm) the fan is moving (therefore the highest static pressure), the less work it is doing as well because it is using less amps and less HP?

Thanks for doing this and confirming what I thought. Good to know I was right on at least one thing
yesterday (haha).

[Neil Brooks]

I think it's great and useful info, John, and appreciate you taking the time to ... do your day job, on your time off

It sure paints a clear picture of why ... the "right way" to design a DC system starts backward, from the machines and their CFM needs, then moves to properly sized ductwork, then figures total SP for a given duct layout, and THEN chooses the DC that will deliver that CFM at that SP.

And it puts it in black and white.

Very cool !

[Neil Brooks]

James: yup. You and Dan had it right, all along.

[james glenn]

James: yup. You and Dan had it right, all along.

Neil, I was just reciting something I learned someplace else. But sure am glad John ran the tests and
backed me up. I would hate to have passed out bad info.

Makes me think about how I calculated mine and if I should do it again to be sure. haha

[Neil Brooks]

Makes me think about how I calculated mine and if I should do it again to be sure. haha

That's what I DO think is really useful about this sort of info

By the way ... and straying only SLIGHTLY off-topic, this time

I was surfing ClearVue's site, the other day, and see where THEY recommend that -- no matter HOW good your DC is -- you wear a respirator, all the time, while woodworking.

That said a lot to me. I really like my 3M 7500, but ... I do NOT wear it all the time.

I'm thinking about starting, though. Luckily, it's NOT uncomfortable.