Wiring a single speed furnace motor for blower use

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  #1  
Old 07-18-13, 08:06 PM
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Wiring a single speed furnace motor for blower use

Hello,

I'd like to wire a Marathon B207 single speed reversible motor to a wall plug for a garage blower set up. The motor is currently wired to run counter clock wise, I'm fine with the direction I'm just not sure how to wire a wall plug to the unit. It appears to draw around 6 amps so it shouldn't be a problem.

Is it as simple as connecting the white and black cord leads to the blue and yellow terminals and the ground to the case? Please see the attached pictures. Thanks for your help.
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Old 07-18-13, 08:45 PM
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Welcome to the forums!

Pick up a three wire appliance cord.
Connect the green wire to the ground screw. (You might need to put a ring terminal on the wire.)
Get some spade terminals and put them onto the black and white wires.
Following the diagram on the motor, place the black wire on terminal #4, put the white on terminal #1
 
  #3  
Old 07-19-13, 10:32 AM
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I plan on using an appliance cord as I have a couple of them laying around.

So the blue and yellow wires pictured are only used to determine which way the motor spins? So if I were to reverse them it would spin counter clockwise correct? If line 1 and line 2 represent the power terminals and I'm running AC, does it matter which of the terminals the black and white connect to? Is line 1 typically hot and line 2 typically neutral?

Thanks for the help
 
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Old 07-19-13, 11:15 AM
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Following the wiring diagram on the label on the motor, you must connect the white neutral conductor to terminal #1, which is the terminal with the empty male spade connector to the right of where the yellow wire is connected.

Connect the ground wire in your cord to the green ground screw.

If you want the motor to spin clockwise, follow the right side of the diagram and connect the black wire in your cord and the yellow motor wire to terminal #4, and the blue motor wire to terminal #5. If you want the motor to spin counterclockwise, follow the left side of the diagram and connect the black wire in your cord and the blue motor wire to terminal #4, and the yellow motor wire to terminal #5.
 
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Old 07-19-13, 11:25 AM
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A furnace blower will pull too much amperage when not connected to a furnace and duct-work, the motor will overheat and burnout, you need to unload the motor partly by blocking off some of the air flow, use a amp-meter and block off airflow and read the amps if its over 6 amps the motor will overheat.
 
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Old 07-19-13, 02:12 PM
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Originally Posted by Flow566
If line 1 and line 2 represent the power terminals and I'm running AC, does it matter which of the terminals the black and white connect to?
As you would guess, there is no polarity with A/C and it simply does not matter in operation, however, there can be a "design polarity" that specifies the hot side to one terminal or the other. In appliances, it is favorable to have the neutral of the appliance switched, while the hot is placed behind the appliance's load.

Originally Posted by braether3
A furnace blower will pull too much amperage when not connected to a furnace and duct-work, the motor will overheat and burnout
Don't let this confuse you. If you are simply using the motor, and not the blower assembly that was originally paired with the motor, this does not apply to you. The blowers in furnaces are matched to a motor under the consideration of a higher static pressure.
 
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Old 07-19-13, 03:36 PM
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Hey Nick,

I am just using the motor to power an aftermarket blower assembly (essentially a caged fan with a drive pulley). The motor will only have a light load on it from spinning a belt between the two assemblies.

I believe the motor was originally cooled by airflow within the system. My HVAC knowledge isn't extensive so I'm just speculating on that idea.

I did stop by a local motor shop today to purchase hold down clamps, the gentleman's opinion, I'd be lucky to get 30 minutes of run time before the unit overheated.

Any chance you can elaborate on "higher static pressure" in layman terms?
 
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Old 07-19-13, 04:23 PM
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Originally Posted by Flow566
I believe the motor was originally cooled by airflow within the system.
Maybe, maybe not. At any rate, the motor itself gives no indication of an air-over rating. This might be literally "AIR OVER" or an acronym like TEAO, Totally Enclosed Air Over. (Your motor is not Totally Enclosed)


Originally Posted by Flow566
the gentleman's opinion, I'd be lucky to get 30 minutes of run time before the unit overheated
Did he elaborate? Did he fully understand the situation?

Your motor is rated for 6.1 Full Load Amps and 6.9 Service Factor Amps, which is taken from the Service Factor. You want to be simple, just consider 6.1A your maximum permissible amp draw.


Originally Posted by Flow566
Any chance you can elaborate on "higher static pressure" in layman terms?
Basically, you're dealing with the flow constriction factor of the ductwork, synonymous to a straw in a drink. Squirrel cage blowers (as opposed to traditional radial fan blades) are loaded less by a higher intake flow pressure. Block the intake on a blower and you'll hear the fan speed up.
 
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Old 07-19-13, 07:29 PM
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Squirrel cage blowers (as opposed to traditional radial fan blades) are loaded less by a higher intake flow pressure. Block the intake on a blower and you'll hear the fan speed up.
It actually is because of mass air flow and not any pressure changes. By restricting the inlet you reduce the volume of air being pumped just as any other centrifugal fluid pump. Reduce the mass flow and you reduce the amount of power needed. Restrict the discharge and you have a similar reduction in mass flow but in this case it is because of increased back pressure.
 
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Old 07-20-13, 09:02 AM
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"In appliances, it's favorable to have the Neutral of the appliance switched"

Art 404 , Switches , (B) , Grounded Conductors----" Switches --- shall not disconnect the Grounded conductor of a circuit."

Art 422 , Appliances , Disconnecting means ---- " A means shall be provided to simultaneously disconnect the appliance from all Un-Grounded conductors -----"
 
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