[RFI] HVAC - some observations

[EDWARDS, EDDIE J]

Karin, 

Did you report this RFI problem to the FCC?  

Here's there complaint page: 
https://consumercomplaints.fcc.gov/hc/en-us/requests/new?ticket_form_id=38844 

The FCC may do little to respond, but if there are very few complaints, then it's not an issue to them.  

No or few FCC reports = No FCC problems.  

73, 
 de ed –K0iL
 Eddie Edwards
 Omaha, NE

-----Original Message-----
From: RFI <rfi-bounces+eedwards=oppd.com at contesting.com> On Behalf Of David Eckhardt
Sent: Monday, July 25, 2022 12:26 PM

And again and again and again and again,...........WHERE IS THE FCC? ? ? ?
? ?  !  ! !! !! !! !!!

Dave - WØLEV

On Mon, Jul 25, 2022 at 4:40 PM Karin Johnson <karinann at tampabay.rr.com>
wrote:

> Hello Group:
> Given the recent discussion about HVAC systems and RFI, I am writing 
> this to chime in on an issue that I haven't seen on this reflector.  I 
> have had a brief discussion with another ham that has the same type of 
> system, manufactured by the same vendor.  His experience is similar to 
> mine.  He went a step further than I did and placed many type 31 
> toroids on the 240 volt power feeding the compressor, but did not see 
> any decrease in RFI.
> Now to the details.
> About two years ago I had to replace my HVAC system.  I wound up 
> having a Rheem model RP1748AJVCA unit installed. This system uses a 3 
> phase motor in the outside compressor unit.  The 3 phase motor is 
> driven by an inverter that is housed in the outside unit enclosure.  
> It is bonded to the enclosure via its mounting mechanism.  The control 
> interface from the thermostat and air handler is via RS-485 two wire 
> communication which is routed along with the 24VAC power voltage for 
> the outside electronics.  Suffice to say this is an evil system with 
> regard to RFI.  The initial installation did not have the 
> thermostat/control wiring replaced with shielded type.  I had the 
> installer come back and replace the wiring with shielded type wiring. 
> This helped a bit with the RFI.  I also installed type 31 toroids on 
> the control wiring at the compressor and also at the air handler.  
> This simple solution knocked the RFI down about only 6 dB.  Note the 
> RFI is most pronounced from about 4 MHz to 18 MHz. The remaining RFI 
> is caused by the inverter running the 3 phase compressor.  The noise 
> floor increase due to the RFI is about
> 20
> dB, between the compressor being off and the compressor being on.
> Some time ago I believe I had posted a Google Drive link to some 
> documentation I developed showing the spectrum analyzer plots taken 
> with the system off and the system on.  I might note that the power 
> feeding the compressor inverter control board does have some internal 
> filtering, by using toroids of unknown characteristics to me.  Along 
> with a substantial filter board, which appears to be a common mode 
> filter mounted inside the metal enclosure of the outside compressor 
> unit.
>
> My intent of this post is to simply inform folks to be aware of newer 
> HVAC systems that use 3 phase inverters to drive the compressor motor.
> I have done a bit of design work to implement a possible solution to 
> the RFI but its cost is prohibitive at this point in time.  I would 
> also have to dis-assemble the filtering boards and components on the 
> outside compressor unit.  Probably voiding the warranty.
>
> So in conclusion, folks, please do your homework and due diligence to 
> investigate what type of technology the new HVAC system is going to use.
>
> Regards,
> Karin Anne Johnson P.E.  K3UU
> Palm Harbor, Florida
>
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--
*Dave - WØLEV*
*Just Let Darwin Work*
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