Question - Squirrel Cage Fan

Re: Question - Squirrel Cage Fan

Bill Howatt

>Blocking may or may not be necessary. Have you noticed the noise a vacuum cleaner makes when it gets plugged? It revs up because the fan inside doesn't have as much air to move so the motor can rev up due to the reduced load. Blocking has the same effect for your fan.

IMO the best way is to put a clamp-on ammeter on one motor supply lead and measure the current draw. It should be equal or less than the rating on the motor. If it is too high, partially block the inlet until the current falls to a safe range.

Be sure you put your fan in an enclosure with good quality furnace filters as a minimum. The motors are designed for clean air - not dusty air.

HTH,

Bill

They are also great in the back yard

Wayne Cooper Charlotte NC

>Jerry

I can't imagine that you would need to block air from either end. I pickup the squirrel cage blowers from old heating system all the time. I mount them on cheap 'two wheel hand trucks' and use them in the garden and deck to move air in the hot summer. They are much quieter than a regular fan. I wire up two-'three way switches' to control the three speeds on them. I also go to HF and pick up a 25 foot extension cord and wire it in permanently. I have given some to the neighbors and they are big hits at parties. Wayne Cooper Charlotte NC

Re: Question - Squirrel Cage Fan

James Brooks in GA.

>Jerry , the only true way you can tell is with an ampmeter, but having dealt with motors all my life I can almost say for sure by the fan coming from an HVAC that you will need to restrict the exhaust side. The reason is the fan was designed to be used with air duct which creates the same back pressure that you will by closing off the exhaust. You will notice that the fan will actually speed up by doing so. There are fans designed not to be restricted, but this is not one of them.

Re: Question - Squirrel Cage Fan

Lee Weed

>Jerry,

Take a piece of wood or something that you can use to slowly cover the opening. Starting at the bottom cover a small portion and gradually increase the area. you should be able to tell when you reach the proper coverage by listening to the motor.

It will make sense when you do it:)

Lee

Re: Question - Squirrel Cage Fan

Jerry Whitaker

>Since I do not have an ampmeter, I think I will try covering it up and listen for the sound. I got this fan for free so I would like to use if it possible. I was looking in the Grainger catalog and they have some that are belt driven which I think will not have the back-pressure problem but they are larger and very expensive.

Thanks everyone...

Re: Question - Squirrel Cage Fan

EagleS.C.

>Any squirrel cage fan whether it has a belt or not can over heat.

Some have an automatic overload that will shut them down.

The analogy of the shop vac is a good explanation.

It is easier to restrict the intake than the exhaust and from past experience it works better.

A squirrel cage fan will turn and move as much air as you can give it.

The motor however may pull more amps than it is rated for if the intake is left completely open.

I know this seems counter intuitive but trust me.

It's true.

The same issues apply to a Dust collector motor designed to run 4" duct and the opening is enlarged for 6" duct.

You may get away with it for a while but it is not doing the motor any good.

A clip on ampmeter is a good investment for checking out amp loads in the shop when using more than one power tool on the same circuit.

(HVAC sheet metal fabricator for 16 years)

(Your mileage may vary)

Re: Question - Squirrel Cage Fan

Barry Irby

>Ignorance is Bliss. I have a squirrel Cage blower that I have had for more than twenty five years. I put it in a crude box and installed it in a window in my shop to suck air through and out. I used it with a filter in one side as part of a spray booth. I recently added a window AC to the shop and converted the blower into an air cleaner. I cut the box to pieces and put filters all the way round. I have course ones on three sides inlet cleaner and another finer one on the outlet. So It has run for years without restriction and continues to run with restrictions. I must have been lucky when I picked it up at the dump.

Re: Question - Squirrel Cage Fan

Bill Howatt

>Probably lucky but don't know to what degree. I got a furnace fan from a friend and fired it up on the floor in "free air" and it ran right on the rating.

Just putting it in a box with a filter will add some impedance to air flow.

Bill