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Condenser fan motor? (14 Posts)
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Condenser fan motor?
1075 RPM motor,has 2 speed taps,hi and low. What is the hi and lo RPM?
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RPM
Look on the data plate of the motor. The low is usually about 70% of the high. It is actually a horsepower tap more than a speed tap. With no load, the motor would run at the same speed on either tap. With a load attached (the fan), the motor slows down on the lower horsepower tap. This is why you should not increase the horsepower when replacing a multi speed motor.
Bob
You can choose to do what you want, but you cannot choose the consequences.
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SPEED
HI Robert, usually it's 850 rpm w/ 1075 as the hi
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Right On!
Lo speed will typically be between 750 and 850 on that motor. When in doubt, use a tachometer on the shaft to measure accurately, as all motors will vary somewhat.
Eugene
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Thanks!!
Long story short,had a job yesterday with a bad condenser fan motor. All I had was a 1075 rescue motor,existing was 1/3 horse 825 RPM. At high speed,the new motor goes into overload fairly quickly. I assumed the fan was overloading the motor at the higher RPM,at set it to low speed with same result. Coil is clean and voltage good out of contactor.
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Motor
Is the rotation of the motorcorrect and the cond fan blade?What HP is the new motor at 825 rpm?
This post was edited by an admin on July 3, 2011 5:51 PM.
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Over load
I dont see how the new motor could go into over load just bc u change the hp.Sound more like a bad run capacitor to me.
Is this a three or four wire motor?
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Right
Right rotation,new cap. Can a fan designed for 825 overload a 1075 motor?
This post was edited by an admin on July 4, 2011 11:40 AM.
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RPM
The new 1075 rpm motor is still running at 1075 rpm even on the lower hp tap,so the fan blade will overload the new motor. Plus the cap size changes 208v vs. 230v You need the Rescue motor #5464 @ 825rpm
This post was edited by an admin on July 4, 2011 12:40 PM.
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Rescue motors
How does one motor do it all? At pretty much the same speed [ hi 3/4 hp = 1110 rpm ,lo 1/5 hp= 1140 rpm ] Why not just use a 3/4 hp in all lower hp applications ?
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Inverse Porportionality
is the words the Emerson Motor Engineer used to describe what would happen to a 3/4 hp motor used in a 1/5 or 1/4 hp application.My motor repair shop guy said "The damn thing will overheat on you " The Rescue condensor motor line has a "special" winding w/ two taps ,both @ 1075rpm ,but different HP's
This post was edited by an admin on July 6, 2011 7:57 PM.
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just a little read
from Fasco Motor Facts
FACT Modern multi-speed motors are really not multi-speed,
but multi-horsepower. The speeds are simply taps at different
points in the coil. The higher speeds are tapped at a point with
fewer turns as compared to where the subsequent speeds are
tapped in the same coil. The more turns that are wound before a
tap is brought out, the lower the horsepower will be each time.
Obviously, the lowest speed lead is connected to the end of the
last turn on the coil. These added turns weaken the motor. This
field weakening allows the load to slow the motor down each
time a slower speed is selected. With no load mounted on the
shaft, as with a bench test, no difference between speeds will be
seen. If too strong a replacement motor is used on a unit, there
may be no appreciable difference when the speed is changed in
the unit. Remember, the motor relies on the load to slow it down
between the speeds. As an example, if a 1/2 HP three speed
motor is used instead of a 1/4 HP three speed, there might not be
any noticeable difference between Hi, Med, and Low.
NOTE: A motor nameplate showing 1350 RPM is a special design
and must be replaced with an OEM direct replacement. This is a
high slip 4 pole motor, which is not generally available in a general
line of motors. If one is available, it would be marketed as an OEM
direct replacement motor for a specific piece of equipment. These
motors are specially designed for a very specific load.
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The correct motor
solved the issue,the 1075 was pulling over 5 amps at low speed,the motor is rated at 2.1 amps. I didn't realize a prop fan could be that different?
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The correct motor
solved the issue,the 1075 was pulling over 5 amps at low speed,the motor is rated at 2.1 amps. I didn't realize a prop fan could be that different?
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