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November 10th 06, 08:47 PM
posted to alt.home.repair,rec.radio.amateur.misc,rec.radio.amateur.antenna,rec.radio.amateur.policy,alt.hvac
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Trane furnace radio/TV interference
Dave wrote: Mark wrote: modelman wrote: Several months ago I had a high efficiency Trane XV90 natural gas furnace and heat pump installed. Since the weather has recently been cold enough for the gas furnace to provide heat, I have been experiencing severe radio interference. The interference wipes out AM broadcast reception throughout my house. I also see snow on a TV connected to an external antenna. The radio noise occurs as soon as the draft inducer motor starts up; the pitch of the interference is related to the motor speed. The draft inducer motor is a dc motor driven by a PWM controller on the main circuit board. ... SNIPPED ... DC motors are notorious noise generators. Those of us who used to be mobile when 6 VDC was the value of a car battery, and alternators did not exist, will attest to the facts of generator [DC motor] noise. A DC motor uses brushes to contact windings within the motor. As the motor turns the brushes continually make and break current in the rotating armature [inductance]. This making and breaking creates a very wide HF and lower VHF noise spectrum. [Lots of sparks]. The solution, in the olden days, was a coaxial capacitor mounted directly to the frame of the motor with the DC power running through the capacitor. I recall the capacitor was about 1 inch in diameter and 2 inches long. Sprague made such a critter. Hope this history helps. /s/ DD, W1MCE I'm pretty sure these motors don't have brushes and are electronically commutated and the electronics are causing the EMI... Mark |
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