6" Duct on Jet DC1100C

[Gary Chester]

Sorry Sonny... but you are incorrect... and I CAN prove it with an ammeter.

My cyclone draws 11 amps with all gates closed. It draws 14 amps with one gate open.

Start up current is scary!! maybe 60 amps for a couple of seconds!!!

[Bill Keehn]

From what I've read, most motors are going to reach a speed of 3450. Sonny is right in that regard. So under heavier load the motor will draw more current in order to maintain speed. Without some form of overload protection the motor will burn out under a constant heavy load. I'm not sure all manufacturers are the same in that regard.

Gary the question I have is what current does your motor draw when it the bag and the impeller cover are removed? Is it enough to burn out the motor and how do you know without burning it out?

[Gary Chester]

Hey Bill, I cant answer the last question as the cyclone doesn't have the "bag and impeller cover" per se... I suppose I could remove the bag under the filter to lessen the resistance to the air flow... but I don't have much interest in doing that... too lazy.

But I used to have the same 1100 that you do, hooked up with 6" S&D everywhere and it worked very well for me. FWIW, all my gates were 6" except for one, and you could see big difference in how fast the dust was spinning in the bag with the 6" gate vs the 4" gate opened. Not a scientific test... but it certainly told me something.

I don't think I'd run that 1100 longer than it takes to take a current reading with nothing connected to either side of the blower. Then I'd compare that reading to the max amp rating on the motor.

Another thought... some folks here run their blowers to just blow the dust thru the wall outside, no bag, no filter, and I don't remember hearing about burned out motors from them. But they have the resistance of the ducting to limit the air flow and current.

I'm pretty sure I didn't answer your question...

[Sonny Edmonds]

Bill, different manufacturers will show different synchronous speeds for their motors because of bearing resistance, magnetic slip, and windage within the motor from the internal cooling blades (fans) on the rotor.
These resistances will drag down the true synchronous speed from 3600 (2 pole), 1800 (4 pole), 1200 (6 pole), or 900 (8 pole) RPM.
So the result can be a wide array of actual RPM when running. (like 1725, instead of 1800, or 3450 instead of 3600)
__________________________________________________ _____

For the pickel heads:
What most of these shade tree shop electricians don't know is the motor can only reach it's design speed minus the forces of it's load. The manufactures don't want to buy everybody motor after motor, so they design their machines to operate within reasonable confines of the motors used. Or they bump up the HP to prevent overloading. A Friend in Texas had Onieda send him a 3 HP cyclone because they were back ordered on the 2 HP he had ordered. Same cyclone, same wheel, just the bigger motor.
Not good for power factor if you were to run a lot of them. But he is a one man shop.

But hey, what do I know? After all I've only been a professional in the electrical field for 40 some odd years. Industrial and utility power installation and maintenance work. Every work day, all day.
All I can say is my junk hasn't burned up. Not my shop vac, nor my dust collectors (any of them), nor my dirty air booster blowers I have or had in the past. In any of the many configurations I have run them in.
But heck, let them eat cake, for all I care. It's not my money they waste.
I bypass most of these threads because of the ignorance I see thrown out as some kind of fact when I know better from actual experiance. Anybody who buys a shop vac that doesn't have a seperate fan to cool the motor is a cheap fool.
And you can not mix shop vacs series wound (Universal) motors, with induction motors intelligently. They are completely different motors.
I have run my shop vac in a manafold system, against closed gates until I needed to open them, for over 10 years. The same shop vac.
So how come it hasn't burned out, Geniuses? How come my dust collection systems haven't failed?
Oh Gee! Maybe I know what I am doing?

[Phil Thien]

I have run my shop vac in a manafold system, against closed gates until I needed to open them, for over 10 years. The same shop vac.
So how come it hasn't burned out, Geniuses? How come my dust collection systems haven't failed?
Oh Gee! Maybe I know what I am doing?

Running a shop vac as described (with all the inlets closed) is easier, not harder on the motor. It sounds like it is working harder because the pitch increases as the motor spins faster. But it is actually drawing less current.

Think of a blower like a table saw. Just like a table saw's motor will be under more load cutting thick stock, the blower's motor is under more load moving lots of air.

DC designers typically assume some plumbing on the inlet (at least a 10' hose) and a filter on the outlet when sizing their motors. It is a fairly safe assumption, as a blower with no filter and no hose is pretty worthless when it comes to collecting dust.

[Sonny Edmonds]

I am fully aware of the unloading, Phil.
But the statement that running a shop vac without air will burn out the motor is false with any reputable vacuum that has a separate fan for the motor, such as rigid and Craftsman 16 gallon shop vacs. The most common ones I know of.
There are a lot of bogus ideas floating around on the Internet about how this will cause that to fail. Have been for well over a decade.
Perpetuated by statements like this:
http://www.sawmillcreek.org/showthre...97619#poststop
And specifically this:
"Dust collectors are almost all cooled by an external cooling fan, unlike a vacuum cleaner that depends upon the air going through the system to keep all cool."
Categorically false. Unless talking about the really cheap ones that are throw aways.
But people grasp onto these falsehoods as some sort of gospel.

Stopping the air flow to either will unload the unit, amperage wise. But an induction motor will only go to it's synchronous speed minus friction loads and stay there.
A Universal type motor can wind to destruction, or at least to it maximum commutation thresh hold. Then the commutator bars will eventually destruct from centrifugal force.
But a dust collector, with it's final filtering media, and being capable of doing it's job, moving air, is not going to go into overload with out some serious design deficiency from the manufacturer.
Straight out of the box, or even with a 6" duct attached, I do not believe it is possible to force it into overload.
I've worked with and experimented with too many configurations to believe that. And that is based on experience, not some frenzy on the web.

[Paul Demetropoulos]

Bill, different manufacturers will show different synchronous speeds for their motors because of bearing resistance, magnetic slip, and windage within the motor from the internal cooling blades (fans) on the rotor.
__________________________________________________ ___

For the pickel heads:
What most of these shade tree shop electricians don't know is the motor can only reach it's design speed minus the forces of it's load.

But hey, what do I know? After all I've only been a professional in the electrical field for 40 some odd years. Industrial and utility power installation and maintenance work. Every work day, all day.
All I can say is my junk hasn't burned up. Not my shop vac, nor my dust collectors (any of them), nor my dirty air booster blowers I have or had in the past. In any of the many configurations I have run them in.
But heck, let them eat cake, for all I care. It's not my money they waste.
I bypass most of these threads because of the ignorance I see thrown out as some kind of fact when I know better from actual experiance. Anybody who buys a shop vac that doesn't have a seperate fan to cool the motor is a cheap fool.
And you can not mix shop vacs series wound (Universal) motors, with induction motors intelligently. They are completely different motors.
I have run my shop vac in a manafold system, against closed gates until I needed to open them, for over 10 years. The same shop vac.
So how come it hasn't burned out, Geniuses? How come my dust collection systems haven't failed?
Oh Gee! Maybe I know what I am doing?

Well maybe, but you're usually a little nicer about it.

And anybody who buys a shop vac and doesn't have a separate fan to cool the motor is a cheap fool? This implies that the fool in question knows he should have it but is too cheap to buy it. More likely they don't know they need it and thus fall into the category of ignoramus, not fool. And I'm not cheap either!

[Sonny Edmonds]

OK, Paul, ignoramus then. That has a more sophisticated ring to it anyway.

One thing for sure is I wish my old (12 years now?) rigid shop vac would die so I could justify getting Keith's vacuum.
Sigh! But it still has a vacuum motor....
I need one of the ones from one of the places I used to work. 10 HP, 3 phase 480V, probably 20 stages in the vacuum pump.
Ran all day. Cyclonic, HEPA, and a 55 gallon drum.
Dream big!

[Bill Keehn]

Sonny,
The funny thing is the Jet DC has no warning in the manual of running it unloaded, but my Rigid shop vac manual actually does warn against running it without the filter/cannister/hoses attached.

The only warning for potential burnout I've seen in dust collector manuals is when the impeller becomes jammed.

[Phil Thien]

Straight out of the box, or even with a 6" duct attached, I do not believe it is possible to force it into overload.

I still don't think we're on the same page.

Perhaps a better way to put that would be, "With a 6" duct attached, or even straight out of the box, I do not believe it is possible to force it into overload."

That is because, adding filtering and adding ducting REDUCES the workload on the motor, and therefor the likelihood over overloading.

I only mention it because it is confusing for many readers new to this topic.

On your point of "not in the real world," I do agree somewhat. I think the risk has been exaggerated. But, ammeters are cheap and handy to have around. So it probably wouldn't be a bad idea for the average shop user to have one and test their system.

[Sonny Edmonds]

Bill, mine has the removable head so it can be used as a leaf blower.
Nothing to slow down the air at all. Unless one length of 2 1/2" wand counts.
I've actually used it like that, too. Kind of handy.
But I eventually needed a chipper/shredder for branches, so I got a Troy lawn vacuum for the yard duties.
To reiterate, 12 years and still working. Darn thing.

[Sonny Edmonds]

Here's a picture of my old Harbor Freight blower in it's last configuration in the old shop before we moved.
If ever a blower was put through paces it was this one.
This "little blower that could" pulled, pushed, cycloned, and even blew leaves on occasion.
Because it was the experimental base blower.
It never failed, never tripped it's overload, and even ate a nasty knot when it was brand new. Scary wasn't the word for that chunk being wanged around before finally passing out of the blower housing.

Who, besides me of course, would go so far as to actually carry around a dust collector blower and blow leaves into a pile from 2 prolific fruitless mulberry trees? And put the little devil into service as a dirty air booster blower?
I finally let the little booger go to a friends helper along with my home made 100 gallon cyclone and some ducting to get him started.
Still ran fine, still never had any overloads counted on it's trip.
You can't get much more free flow than blowing leaves around.
It was a 1 HP, 660 CFM, 120 volt little dude. Came with a side bag when new. Probably about like burlap for filtration specification.
In the picture, it was kicking everything in the system to the cyclone and a 1200 CFM Delta bagger outside the shop. The old shop was a test bed and lab for the new shop.