Discharging dust outside

[rattletrap]

I plan on discharging dust outside my shop thru the wall.  I want to build the seperator.  I do not want to burn my blower motor up due to the fact I will not be going thru a filter.  Will the Thein seperator provide enought resistance to AMP down the motor so it won't burn up.  Also if I am successful in building the seperator can you use a plastic bag in the seperator to collect the heavies?

[retired2]

I plan on discharging dust outside my shop thru the wall.  I want to build the seperator.  I do not want to burn my blower motor up due to the fact I will not be going thru a filter.  Will the Thein seperator provide enought resistance to AMP down the motor so it won't burn up.  Also if I am successful in building the seperator can you use a plastic bag in the seperator to collect the heavies?

Amps go down as the load decreases, not up.  Amps reflect the amount of work peformed, so as load or cfm's increase, the amps will go up, not down.

[Bulldog8]

It sounds like the OP understands that running without a filter will increase the amps his motor is pulling.

Will the Thien Baffle provide enough resistance to bring your amp draw down to an acceptable level even though you are not running a filter? I has for many, but I feel that there are too many variables to give an answer. The size of your duct, leaks, 90's, number of blast gates open, will all change the amp draw. An amp meter is a handy thing to have; I'd suggest getting a clamp on meter and test "your" set up under real working conditions.

[retired2]

It sounds like the OP understands that running without a filter will increase the amps his motor is pulling.

Yes, that is what he believes, but as I said that is incorrect.  All other things being equal, removing the filter will lower the amps, not raise them.  In fact, the lowest amp reading will occur when the blower and motor are running with no piping or filter is attached. So, adding a separator does not "amp down" the motor, it causes amps to go up.

[phil (admin)]

It sounds like the OP understands that running without a filter will increase the amps his motor is pulling.

Yes, that is what he believes, but as I said that is incorrect.  All other things being equal, removing the filter will lower the amps, not raise them.  In fact, the lowest amp reading will occur when the blower and motor are running with no piping or filter is attached. So, adding a separator does not "amp down" the motor, it causes amps to go up.

No, it is the other way around.  The more air the unit is moving, the more work it is performing, the more amps it is using.  Adding resistance anywhere (ductwork, filter, separator, etc.) means the unit is moving less air, so doing less work, so using fewer amps.

BTW, I know you know this.  Were you having a minor brain aneurism as you typed that?  :)

[retired2]

It sounds like the OP understands that running without a filter will increase the amps his motor is pulling.

Yes, that is what he believes, but as I said that is incorrect.  All other things being equal, removing the filter will lower the amps, not raise them.  In fact, the lowest amp reading will occur when the blower and motor are running with no piping or filter is attached. So, adding a separator does not "amp down" the motor, it causes amps to go up.

No, it is the other way around.  The more air the unit is moving, the more work it is performing, the more amps it is using.  Adding resistance anywhere (ductwork, filter, separator, etc.) means the unit is moving less air, so doing less work, so using fewer amps.

BTW, I know you know this.  Were you having a minor brain aneurism as you typed that?  :)

Sorry guys for giving you such backwards info - talk about feeling stupid!  And especially after I took so many amp readings during testing of my build.

I'm going to blame my senior moment on being out of my element.  I spent the last four days getting into the Christmas spirit in New York City.  I think the cold wind in those canyons blew my brains out and left only the sawdust for me to think with!

[tvman44]

Adding a slight restriction to the discharge will bring down the amps if needed.: )

[John]

Amp draw is proportional to the work. Generally restricting the output raises amp draw as the fan does more work to create a higher discharge static pressure. And, restricting the input lowers the amp draw as the intake pressure drops.

[jdon]

FWIW, my simple minded picture of what's going on is that the work the impeller is doing is spinning blades against air resistance.

If the intake is restricted (or esp. closed off), there is a partial vacuum, so less air, less resistance to the blades, so less work- and lower amps. [In a total vacuum, the only work the impeller would have is due to bearing friction.]

If the outlet is restricted, pressure builds up in the impeller, so the air is denser, so more resistance, harder for the blades to turn, so more work, and more amps.

[retired2]

Sorry guys, but if you block off the air, whether it is inlet or outlet, the amps will drop.  It is because the impeller is not being fully "loaded".  Work is only being performed if air is being moved.  Reduce the airflow, and you've reduced the work being done and therefore the amps drawn.  Conversely, the best way to overheat a fan motor is to remove all inlet piping, outlet piping, and filters, then just let it run!

[jdon]

Thanks for the clarification!  :)