Hello PICList,

I have jigged up a small (200W, 3600RPM, 10" blade) AC induction
blower unit salvaged from a high efficiency furnace in my basement in
order to "pump out" radon gas. I intend to run the system continuously
for one week while monitoring the levels of radon with a meter.

I have found that the blower motor is not rated for continuous
operation (the internal fan blades for cooling the motor are too
small). While running the motor gets so hot that I cannot touch it
without burning myself regardless of how the fan is loaded.

I would like to know if reducing the RMS voltage to the motor would be
an effective way to reduce the heat generated?

As it stands currently the blower moves more than enough air. If I
understand correctly reducing the applied voltage via triac basised
light dimmer (since I don't own a variac) will cause the motors slip
to increase and the overall efficency to decrease. But since the
applied power is lower and the frequency is the same the overall heat
generated (and work done) should decrease.

I have entertained the notion of adding a second cooling fan to the
motor, or redirecting some of the airflow over the motor, or reducing
the fan blade size, or using a VFD to reduce the speed, or even just
replacing the whole blower unit/motor. I would like to avoid those
particular solutions for the moment unless the current method turns
out to be impractical.

Comments and suggestions are welcome.

--=20
Jason White
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.