Correction: noise is quite *loud* on all stations.
I should add that the American Standard AUY (also known as the Trane XV90) furnace
series is a natural gas furnace with a variable DC brushless blower fan motor. The
inducer motor is variable too, but it may be a brush type motor, causing the
noise. It must be quite a bit because it causes interference on the radio in my
car as I approach the house.
If you've read one of my earlier posts you'll see that replacing the wiring
harness between the inducer motor and the control board (with, per Trane, a
shielded harness) made a significant differnece in the RF interference in
the TV picture. Didn't eliminate it though--at least this gives you some
direction with respect to trying to fix the problem.
I'm gonna GUESS that this motor is also brushless but that it is
variable speed and is controlled by some electronic device that uses
Triacs like in a lamp dimmer and it is this "dimming circuit" that is
actually casing the problem. Can you see any brushes sparking going on
inside the motor? If it is indeed a brushless motor and the problem is
the electronics, I'm gonna also GUESS it's a design problem and you may
have to go to Trane to engineer a solution. Got any ham radio
operators near you. They would be very happy to help you as your
furnace is probably causing them grief.
Because there has been a number of comments/speculation about the inducer
motor I dug out the Installer's guide. Listed under Service facts is the
specs for all of the major components. In the wiring schematic the motor is
identified as a "Vent Motor" and it does not indicate whether or not it is
an AC or DC motor.
The schematic does not indicate that the wiring harness between the motor
and the control board is a shielded harness. Could just be a sloppy
representation of the truth or a recent fix that Trane has been using in
response to the RF noise problem. In the Specs the motor is called a
"Combustor Fan", not to be confused with the Blower Motor. Specs are as
Drive-No. Speeds---- Direct - Variable
Motor HP-RPM-------1/50 - 5000
Volts/Ph/Hz------------33 - 110/3/60 - 180
Just some more info.
On Thursday, March 10, 2005 at 4:30:51 PM UTC-6, MLD wrote:
If the furnace cannot be fixed satisfactorily, I would threaten to contact
the FCC. There are many FCC rules about not causing interference to licens
ed radio services, and this sounds like a flagrant violation of those rule
s. The whole general subject is called "electromagnetic compatibility", an
d there are professional organizations like the Institute of Electrical and
Electronic Engineers that have worldwide members who specialize in electro
Using the battery operated portable am radio is the best that you can do wi
thout sophisticated equipment. See if the noise appears to be radiated int
o the house, or is it being conducted onto the power lines at the furnace a
nd then carried by the power lines throughout the house.
Use increasing frequency to better pinpoint. AM. CB vs AM broadcast.
Aircraft vs CB, etc.
I first noticed FM broadcast interference while taking car out. Turn out to
be my LED outside lights running switched curren limiting. Ferrites helped.
replying to MLD, Slowpoke wrote:
i am having the same problem with my ham radio station.....the vent blower runs
4 minutes then the furnance blower starts while the vent blower still runs for
another 4 minutes then it shuts off and my noise disappears from my radio but
the furnance motor still runs with no noise on my radio.....
please help me get rid of this noise......furnance only 1.4 years
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