I have an old motor-blower assembly from a furnace that i am thinking
of using for an air filtration system. I would like to hook it to a
on/off switch, then to a plug so i can plug it into a receptable.

motor ===== on/off switch ===== plug ->receptable

From the motor assembly, i
see only a two uncolored wires. How do i wire this so that i willbe safe?
Can i just wire it without ground to the switch thten to the two prong plug?
Thanks in advance,

 

There's two answers to that - it depends how safe or unsafe you want to be... :shock:

Use a 3-core cord and 3-prong plug (with the earth connected all the way through, of course), and terminate the earth wire somewhere on the motor's chassis (you'll probably need a lug on the end of the earth wire).

The switch must operate in the ACTIVE (hot) lead, not the neutral - unless the switch is a double pole switch, with switches both active AND neutral.

 

Don't you think that polarity would affect the motor's direction of rotation?

 

For a single phase AC motor, no, polarity does not affect it. Even for non-permanent magnet DC motors, polarity reversal will not affect the DOR.

In order to reverse the direction of a single phase motor, it is necessary to reverse EITHER the starting winding, OR the running winding, but not both.

 

Yes, indeed, AC motors aren't affected, or if they were, the vaccum cleaner would start throwing out the dirt, if just you switched the orientation of the plug... But for DC motors, I didn't know that they could not be affected by the input's sign...

 

Reversal of a DC motor is, in a way, similar to reversal of the AC motor - either the rotor winding, or the stator winding must be reversed, but if you reverse both windings, the rotation remains the same.

 

Regarding the switch - make sure the contacts are rated for the application. Usually in the US the switch will have a current rating in amperes as well as a HP (horsepower) rating to address the inductive properties of a motor load. A switch that doesn't have a HP rating probalby shouldn't be used.

__________________
stevez

 

Thanks guys!! This is the first time i posted here...can't believe the quick reponses. Much appreciated guys!!

I just have one followup question. Since i will be using this in a air filtration system, how must is dust a concern since the the motor is not an enclosed one. Would it be sufficient just to put the motor=blower in an enclosed area, with a filter on the intake??

 

I have done air cleaners in the past. The (blower) motors I used had 3 speeds (high,med.,low). I enclosed them in a box that had 2 openings. Where the air went in I put a electrostatic furnace filter on and where the air came out I put a grill on. It seemed to work great until one day I notice a lot of dust coming out. I picked up a handful of saw dust and drop it by the filter. That's when I noticed that it would catch the larger particles put not the fine dust (the ones that plug your lungs). So unless you can find a really super good filter, it won't work well.

I find furnace (blower) motors are great fans. The bigger ones can blow air up to 40-50 feet. Great to have around when you're working outside on a hot summer day.