Published at 23:12 on 16 November 2011
It never ceases to amaze me how something so simple can be so brutally effective at muzzling the worst radio frequency interference (RFI) sources. The above picture shows the one I installed on the thermostat wires of the new furnace (whose fan motor controller was using those wires as an antenna to spew RFI). It took multiple turns through the core, but I did end up mostly driving the RFI from the new furnace into the local noise floor.
Some Internet searching reveals that some individuals go inside the furnace to install beads on wires. I didn’t want to open it up, because it’s not mine, and I don’t want to void the warranty. I reasoned (correctly) that since it has a grounded metal case, it’s essentially a Faraday cage already and I could address the issue it by dealing with the wires that exit it.
Haven’t gotten around to those two lower yellow wires yet. Was going to put that bead around both sets of wires, but experimentation revealed that the thermostat wires were by far the worst offenders (to the point where I needed to wrap as many turns of them as possible through the bead), and the lower wires (which control the condensate pump) don’t have a very long run outside the furnace anyhow.