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Author Topic: Rheem A/C system rfi  (Read 9639 times)

Posts: 3

« Reply #15 on: July 05, 2017, 07:52:31 AM »

Has there been a resolution to this issue?  I installed a new Rheem home a/c system about 6 years ago, noticed the RFI near a 20M freq. I frequent but never gave it much thought.  Recently I've expanded my ham activities and noticed the RFI across several bands.  As a diagnostic procedure, I decided to use my battery powered Elecraft KX3 with only a short length of wire as the antenna.  What a surprise as I found that RFI to be present using this test methodology, albeit the signal strength (understandably) was diminished compared to reception on an efficient antenna.  I noted also that the signal level diminished proportionatly with the distance from the compressor unit on one end of the house.  My ham shack is on the same end of the house as the a/c unit, so it stands to reason the signal strength is greatest there.

The main point of my commentary however, is to suggest that the RFI is being radiated through the air and not conducted via power lines in the house.  I don't know if I saw any other similar test results posted here, nor have I seen if there is a known fix available, and if so, how does one go about implementing the fix.?

Hope this helps.

Posts: 1980

« Reply #16 on: July 05, 2017, 08:16:59 AM »

first I'd check ground to the cabinet. if not there, it's a code violation, ground the bugger to house ground. bad form to zap the a/c repairman on a hot day.

if a few ferrites common-mode across all the wiring to control board and power don't do it, I'd leave 'em in and install a corcom-type filter inside a safety box inside the cabinet.

your a/c guy can probably find a factory interference kit if he looks for one, or call Rheem application engineering.

Posts: 591

« Reply #17 on: July 05, 2017, 08:25:05 AM »

Looking here may help:

Posts: 5

« Reply #18 on: July 07, 2017, 07:36:10 AM »

I had a similar problem with a Carrier Infinity system. The GE ECM 3.0 blower motor in the air handler took a 5A Corcom 240V line filter (and four female spade lugs) to quiet the line hash. The RS422 data link between the wall thermostat, air handler, and the outside heat pump was also leaking 20M RFI at an annoying level on 14.076. I was finally successful at eliminating most of it by winding common mode chokes on #43 Fairrite toroids with the idea of balancing the RFI current. Had to add the toroids at both ends of the outside heat pump to air handler as the outside heat pump case appears to be RF "grounded".

The Corcom was bought for $5 off ebay and has 60 db suppression from 50 mhz to just below AM BC band. I used a pair of self drilling sheet metal screws to make sure that the Corcom was "grounded" to the furnace case.

I don't know why the outside heat pump variable speed fan did not also require a filter.

Posts: 2331

« Reply #19 on: July 07, 2017, 08:53:16 AM »

Aug 2016 - QST (Pg. 30)
A Tale of Two Air Conditioners
Author: Lee, Robert C., W0GXA
A membership benefit is access to online issues of QST from 2012 to the present.

Posts: 1788


« Reply #20 on: July 07, 2017, 09:19:03 AM »

If you want to get a feel for your ENTIRE RFI environment, see:

I use an SDR as a site survey tool.  I will be moving in April to a new location, and I intend on running this for several days prior to purchasing a home.  It will show you most of the RFI and how it relates to other RFI sources in one view.  The spectrogram takes a day or so to generate, but once generated you see all RFI over a given several mhz spectrum.

Should the need arise, you can use the spectrogram to document a before and after RFI environment image.  Here is my 80 Meter spectrogram from a few months ago:

This covers 24 hours on 80 meters.  You can click the images on the web page to get expanded views...  In fact look at the 40 meter image and you can see a CW contest in play...  Anyway, this will get you a visualization of yor RFI environment, and a way of keeping track of changes over time.
« Last Edit: July 07, 2017, 09:27:19 AM by NK7Z » Logged

For reviews and setups see:
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