I found recently that my furnace was creating terrible RFI on 40m (and 20m
too). I could only hear the strongest stations and could barely see them on my
panadapter.
After much reading I started investigating to see ways to mitigate it. I tried
ferrites at first on the likeliest culprits and even tried a line filter on the
incoming line. Some more investigating and emails to the various component
manufacturers led me to discover the culprit.
It turns out that my Rheem contour high efficiency furnace has a 3-phase draft
inducer motor. Rheem has a control board that creates a pseudo 3-phase signal
from the 110VAC single phase feed.
Now how to fix it? Well it turns out the simplest solution was the best. I
Replaced the four wires that went from the controller board to the motor with a
single 4-conductor shielded wire. The shield was connected to ground on both
ends (this worked best) I'm happy to say my RFI is completely gone. I do have a
3-phase line filter just in case.
Good engineering practices were followed.
I left the factory wires abandoned in place, should I need to plug them back in
for some reason. I also ensured that the wire I used met the same rating as the
original with regards to voltage, AWG, temperature, etc. I also made sure to
use a cable gland so as to both prevent cable strain and to maintain the
integrity of the isolation between the combustion and blower.
73
AC2EV - Don
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|