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HVAC-GE/Emerson variable speed RFI
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by K5DBX on July 4, 2008
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After placing a new Goodman 2 stage/variable speed fan unit HVAC in my home, I found myself with horrible RFI from the GE/Emerson fan controller combo. Since the hash varied in frequency when the blower moter would ramp up and ramp down I knew it was coming from the main blower.
I took 3" wide HVAC "SureTape" (foilized tape used in HVAC work) and laid out the harness from the control board to the GE motor out flat on the counter. I then cut 2 sections of the "SureTape" the length of the wire harness and removed the backing to expose the sticky tape side. I carefully rolled one layer around the harness, ensuring the tape overlapped as not to have any of the length of the harness exposed. I then took about 8" of shield from a RG8U cable and placed about 2 inches over the first layer at the control board end, on the foil side as I begin to wrap the second layer of "SureTape" around the harness. I then folded the braid back over the outside of the foil and double zip-tied the braid over the harness, insuring both the inner and outer layer of braid was under the zip-ties. I used yellow crimp end on the other end of the braid and secured it to the control board mounting screw. This effectively created a double Faraday shielded cable which removed nearly all of the hash.
I also used 2 clamp on ferrites, one over the thermostat wiring, and another over the wiring going to the motor in the combustion chamber. Both placed as close to the control board as was possible. This effectively removed the HVAC RFI issue. (rig is less than 10 foot from the unit)
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RE: HVAC-GE/Emerson variable speed RFI
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by N8EKT on July 5, 2008
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Good work!
But I pitty the poor service tech that has to change that module LOL =)
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RE: HVAC-GE/Emerson variable speed RFI
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by K5DBX on July 6, 2008
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Why? No mods are done to the board itself. The harness that is between the motor and the board have plugs on both ends. The 20~25 leads in the harness were simply zip-tied ever 6 inch or so, so the appearence in the blower cabinet is actually cleaner than before.
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