[RFI] RFI from furnace/air conditioning

[Randy Standke]

I don't know about Lennox in particular, but I was getting RFI from a Carrier furnace.  It had a variable speed motor.  I could see the RFI change as the motor ramped up to speed.  The first thing I did was add a power line filter inside the unit.  This only helped a little.  What eliminated the remaining RFI was running the thermostat cable through some Type 31 ferrite right at the unit.  That cable was about 20 feet long and made a good antenna for the conducted RFI on it.  In summary, suspect filtering may be needed on all wires connected to the HVAC unit.

73,

Randy KQ6RS

-----Original Message-----
From: RFI <rfi-bounces at contesting.com> On Behalf Of D C _Mac_ Macdonald
Sent: Friday, November 2, 2018 4:05 PM
To: RFI Group <rfi at contesting.com>
Subject: [RFI] RFI from furnace/air conditioning

I have fairly recently gotten back on the air after a few years off.  This is AFTER I had to have our HVAC replaced.  It is a Lennox SL280UH090V48B-03 which is a variable BTU and variable speed fan system.  Lots of trash, especially on 20 meter band.  Does anyone here have experience with Lennox systems in general or my specific unit ?

73 de Mac, K2GKK/5​
(Since 30 Nov '53)​
Oklahoma City, OK​
USAF Retired 61-81​
FAA Retired 94-10

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