"Wen-King Su" wrote in message
...
In a previous article "Steve@carolinabreezehvac"
writes:
:
;Afraid not..and it can be proven with a remote tach.

http://www.engin.umich.edu/labs/csdl.../ac/induction/

As you can see, the speed of an induction motor does not vary much
around its full-load speed over its useful load range. If you increase
load on it, it slows down a bit and then stalls. If you take away all
load, it doesn't go faster than the syncronous speed, which is only
slightly faster than the full-load speed.

If you didn't understand what I meant before, I said this fact
contradicts your claim by implication that the motor will not last long
because it will spin itself into destruction when the input is
blocked:

I know what you said, and I say you are still wrong...and I gave you a
method to prove it...its one of those tools that a good professional will
invest in to make sure your furnace is fully, and correctly
operational...but....I doubt you want to go buy one just to prove
it...so...believe what you will.
Got news for you...block the filter, and the possibility exists you will be
putting a motor and a cage in the unit...

h

"Blue" wrote in message
...
It is counterintuitive but "pulling a vaccuum" is easier on the fan
than
moving air. To see that in action try holding your palm against
the
intake
of a hair dryer. The motor speeds up.

Your reply:
And do that to a CAH and you get a motor that does not last long..

As any speed up from reducing the load will be quite minimal.

Certainly if the motor is completely enclosed and there is no air
circulation, the motor can overheat no mater what load was placed
on it. If that is the case, that should have been your answer to "blue".


No...it should not have been.

Care to post YOUR credentials in this line of work? You can post **** off a
website all day long, that wont make it right.


As it is, with the input blocked, and somehow I can get the normal
amount of cooling to the motor iself by whatever mean, the motor will
run continuously for its designed service life -- because it is not
putting out more heat than it is designed to and not running faster
than it is designed to.

You are right I am just surfing the web for information, and I have
came across several cases where the motor is outside of the conditioned
air stream without seeing one that does it differently. You are
welcome to post your own link.


Go to www.trane.com, www.yorkupg.com, www.carrier.com,
www.goodman.com....the list goes on and on...
EVERY single unit made today has the blower motor IN THE AIRSTREAM.
God are you that dense? What do you do for a living anyway? I own a
sucessful HVAC company...one that purposely trains its techs NOT to do the
normal hit and run **** you people are used to...one that does not have to
post anything in here and can and should prob leave you to the likes of
Dave, and Stormy...since they tell you what you want to hear, not the actual
facts.



If they are in the conditioned air path, I would have to wonder why it
was done that way. Certainly the motors themselves are quite rugged and
can operate at a temperature far exceeding that expected in the air
handler. They have small internal fans and have no problem at all
dumping heat into the air even in a hot attic. Why cut down the
cooling efficiency of the whole system by, in effect, using the
evaportor to cool the motor.

Lemmie guess....you are simply trolling at this point....and you are not in
the trade....bah...believe what you want. You have one (by your admission)
ancient pos furnace that has a thermocouple..you know...stone age units.
Todays units are nothing like that, and if you dont have a clue, and so far,
you dont, dont bother a reply.