[RFI] Trane heat pump RFI

[Wes Stewart]

I haven't been too active lately, so I can't pinpoint when this started but I discovered it on Field Day when I was plagued with an intermittent noise that made me give up.  My local power co-op has been quite good about working these issues, but the intermittent nature didn't bode well for it happening when they were looking.  So I did some sleuthing of my own.  My tribander is about 120 feet from the house and my power line is to the west of it.  The house is NE of the tower.  The noise actually went down when pointed west but peaked when pointed at the house.  I could hear it everywhere from 160 to 6 meters on my Sony ICF-SW7600, even inside the house when it was on.  The problem was it was off more than on.

I had a previous issue with my Internet system causing a problem when the Ethernet cable hooked to the rooftop Wi-Max receiver wasn't plugged in completely by the service guy after an antenna change.  So I went up on the roof (it was 106 deg) with the receiver to sniff around.  Of course the noise was gone by then.

I have a 13-year old, rooftop packaged Trane heat pump model WCZ060F100BD near the Wi-Max system and while I was on the roof, it turned off and the noise erupted.  The heat pump was the source, but not while running.  I could hear an audible buzzing sound inside the box.  I pulled the fuses and all was quiet.  Plug them back in, noise, both audible and RF resumes.  Heat pump turns on to cool and noise is gone.

Investigating inside I determined that the potential relay was chattering when in standby.  When cooling it pulls in, disconnects the starting capacitor and the unit runs normally.  No one but a ham would ever know there was a problem.  Looking at a generic schematic (Potential Starting Relays) I don't see how this can happen.  Clearly, there is more to this.

Unfortunately, Trane (American Standard) guards their schematics like gold in Ft. Knox and I've been unable to find one for further troubleshooting.  I'm open to any and all ideas.  Links to a complete schematic would really be appreciated.

Wes  N7WS