Furnace Blower RPM


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Old 03-12-06, 11:15 AM
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Unhappy Furnace Blower RPM

The contractor that added my central air didn't put a 2 speed motor on. He said he could size the sheve so it would work for heat and air. But the motor runs too faster for the furnace and it takes 2 times for the air to get warm enough to run. How do I determine what size sheves I need to put a 2 speed motor on?
 
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Old 03-12-06, 01:39 PM
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Single speed motor

You would have to change the pulley twice a year. Once in the spring when you went from heating to cooling & again in the fall when you go back to heating. Pain in the tail to say the least. The pulley change would have nothing to do with the temperature at which the fan comes on.
 
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Old 03-14-06, 11:04 AM
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Why can't I just put a 2 speed motor and use the same sheve all the time? I just need calculate the cfm I need and size accordingly, but I don't know how to calculate cfm based on blower size and motor rpm.
 
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Old 03-14-06, 05:12 PM
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2 speed motor

Two speed belted blower motors are hard to come by & expensive. You may be able to use a variable pitch pulley on the existing motor to reduce some of the hassle.
 
 

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