I just had a new Ox Box by Trane furnace installed in my home after the heat exchanger went on my 40 year old Carrier furnace. The furnace will do its normal "ramp up" process, and at the tail end of the ramp up (as air being pushed out of the furnace) I am getting a whining, high pitched, whistling type of noise that seems to originate inside the furnace, but reverberates through my ducts and can be heard in all of the rooms of my house that have vents. The flat-lining noise seems to go away after about 3-4 minutes of operation, but sometimes lingers longer. My installer asked me to put the system on "heat off" and fan "on" to test the blower motor. The blower motor operated without any noise when doing this test. I find it strange that the noise goes away after a few minutes, as I assume if it was simply a case of a new strong furnace whistling through old, outdated and possibly undersized ductwork, the noise would not go away until the furnace turned off. But the noise does go away after 4 or 5 minutes while the furnace continues to heat my home. Thanks for any help or ideas you can provide.
Did the company who installed it leave an invoice and notes about activating the appliance? A standard checklist would include the temperature rise reading. It's possible the blower fan speed can be reduced. You can adjust dip switches 1-4 ON and OFF to achieve a different heating CFM. See the attached blower guide. This may not be for you exact model. The model number would be listed on the rating plate inside the furnace. The rating plate will also state the temperature rise range, and if the fan speed is lowered the temperature rise will increase, so it's important to verify it's still within range.
It's also possible the noise you hear is coming from the inducer motor. It's the first motor inside the furnace to start on a call for heat and it blows the exhaust outside. On startup it's possible it's ramping up to the high fire stage then lowering to the low fire stage. Assuming this is an upflow install you can take the top door off and start a heating cycle and make sure the noise is not coming from the smaller inducer motor. I would verify the venting is not undersized and order a new motor under warranty to see if replacing it makes the noise goes away.
Either way I would call the installing company to see if they have a tech who can verify the heating speeds and check both motors for abnormal noises.