New blower motor on furnace = low air flow


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Old 05-31-13, 11:18 AM
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New blower motor on furnace = low air flow

I have a Payne PG8UUA furnace that had the blower motor go out last night. Went and got a replacement - AO Smith DL1076. So I went from a 1/2 HP 4-speed to a 3/4 HP 3-speed. Installed it, new capacitor too, wired it properly per instructions and everything works fine. I'm getting different speeds for fan, cool, hot.

Only problem is my air flow from my ducts is significantly less than before. Before, at certain vents in the house the vents would blast air like crazy - now just a low whisper. I wouldn't think anything of it at all if it weren't for such a change from previous experience.

Any thoughts? I'm wondering if there is a different way of wiring, or some selection switch to change the fan speed. Alternatively, I'm wondering how sensitive it is to placement of the cage within the housing. The cage is definitely a little closer to motor-side of the housing than the other side. Everything is running and sounds fine. But wondering if I'm going to have decreased performance under high cool/heat loads.

Thanks.
 
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Old 05-31-13, 05:15 PM
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What speeds did you select for the new motor, compared to the old one?
 
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Old 06-02-13, 04:47 PM
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Did you park black on Cool and blue on Heat?
Did you get a new capacitor for the new motor?

 
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Old 06-04-13, 01:06 PM
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Yes, I got a new cap, 15uF because the old motor had a 10uF cap.

Yes, I wired black to cool (hi).

Not sure what is meant by what speeds did I select. I wired as shown below in the diagram. Since I only got a 3 speed motor I lost my yellow wire, but even in cool mode, which should be HI speed for both motors, the difference is appreciable...
 
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Old 06-04-13, 04:12 PM
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Tell us the rated rpm of the hi speed for each of the motors. Motor windings can have different number of poles, which affects rpm. Hi ain't necessarily the same for one motor compared to another.

Upping the horsepower rating of the motor doesn't increase the rpm much if at all.
 
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Old 06-04-13, 04:18 PM
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IS the RPM of the motor different than the previous?
 
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Old 06-04-13, 08:40 PM
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Have you tried switching the white plugs on the motor to reverse the rotation?
 
 

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