Anon wrote:
"Deodiaus" wrote in message
...
I found one for $65 shipped at:
http://boatandrvaccessories.com/43587.htm

Does anyone know where I can buy one for $30?

ps1. I am interested in the start capacitance, (the motor makes the
humming sound trying to start up).
ps2. my friend the electrician is not the same as the AC repairman
and not the same as the earlier guy who put in the 7.5 MFD cap (which
seems to be the one that the sites sell with it [A.O. Smith recommends
10 MFD]).
ps3. The reason I was looking for the calculations is that I can see
how sensitive they are to a change in capacitors.

The motor you referred to is not a cheap motor, it's just not an
exessively
inflated priced motor.
New surplus blower motors can be found at numerous surplus dealers for
about
$30 or less, plus shipping.
snip

Induction motors
are greatly affected by the load upon them. If the load is less than the
maximum, a smaller capacitor value is used to keep the rotation speed within
reasonable parameters. An induction motor run without any load will run too
fast and the windings will overheat and break down the lacquer insulation
causing an internal short.


Not even close. Induction motor speeds vary little from no-load to
full-load (slip from no-load to full-load of typical induction motor
[not some ceiling fan junk] is 1 to 3 % of synchronous speed). Running
completely unloaded is perfectly fine and the windings of an induction
motor will *not* overheat in that situation. (hint, the motor draws less
current when it's unloaded)

If the motor just hums and does not rotate - there is something else wrong.
A failed capacitor results in this same symptom and is the easiest solution
to try, hence the reason it was replaced. Even a 4µF or 5µF capacitor
should turn the motor. Check the bearings by rotating the unloaded motor
shaft - it should rotate fairly easily. Usually sealed ball bearing sets
are used in these motors, pressed onto the shaft - replacement will require
a bearing puller.

If the blower is directly attached to the shaft, the only bearings to check
are in the motor. If it is a belt driven set-up (older), the bearings on
the squirrel cage will be suspect.

If the motor spins freely, but still only hums on start up, either a bad
connection to the capacitor (or other component) or a short or break in the
motor windings, not to mention another capacitor failure. These motors tend
to have very fine and compact winding wraps and then take a lacquer bath,
making service difficult if not impossible. If there is a short in the
motor, the first place to check is the bundle where the insulated wires are
soldered to the winding wires, if that is the connection method.


These are good troubleshooting points. But your statement earlier about
motor speed/load is off.

daestrom