Changing blower motor speeds with Capacitor change?


Old 11-16-04, 03:43 PM
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Changing blower motor speeds with Capacitor change?

I have a Rheem Criterion furnace, and lately it has been very noisy, and I have tried replacing the motor (which I had replaced previously which was a quite motor, but the latest motor wasn't the problem) and now replaced the blower wheel. That helped, but much of the noise appears to be that my 3/4 HP motor just runs at too high of a speed - I don't have temperature deviations around the house and there is plenty of air movement in the vents.

The current Run Capacitor is 15 mFd, the design capacity, but if I replace it with a 12.5 mFd capacitor it should run at 1/2 HP and therefore be a bit slower, correct? I've looked all over the web for a description of the affects of changing the capacitor and whether it would negatively impact the motor itself over time.

Any help would be greatly appreciated, or other suggestions for reducing the fan noise.

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Old 11-16-04, 04:50 PM
Ed Imeduc's Avatar
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Dont work that way the cap is to just start the motor like. You have to have the one that came with the motor. That 3/4 hp should have 3 or 4 speeds on it. look there on the blower door should see the wire schematic for the motor.Most of the time we set them at med for the heat and on high for the AC. On some motor that 370V 15 Mfd will work on a 3/4-1/2-1/3. but not change the Hp


Last edited by Ed Imeduc; 11-16-04 at 05:05 PM.
Old 11-17-04, 05:28 PM
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3/4 hp? what is the model of the furnace?
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