[R-390] High Electrical hash noise level

Wed Mar 30 11:18:46 EDT 2011

Good Luck, You're never going to eliminate the RFI from the PWM motor and drive circuitry. The layout of the contol board and the exhaust motor was accomplished with no concern for ground loops, shielding, etc. If you have metal duct work in your HVAC system it serves as a fantastic radiator for all of that noise being generated from the furnance. As for me 160 and 80 are useless when the furnace is running,40 and up is OK. One amateur suggested I install a remote kill switch for the furnance in the radio room :-).

,
PS. I built my own shielded harness, no effect,ferrites, no effect, lifting safety ground from motor, some reduction but the motor housing is now not NEC compliant!

--- On Wed, 3/30/11, Robert Moses <rhmoses at earthlink.net> wrote:

From: Robert Moses <rhmoses at earthlink.net>
Subject: Re: [R-390] High Electrical hash noise level
To: R-390 at mailman.qth.net
Date: Wednesday, March 30, 2011, 1:16 AM

Small disk ceramic caps across the motor, etc may also be helpful since 
these look like a short at RF .

Steve Toth wrote:

>Bob et al,
>Here's the latest:  I did some digging on the internet.  Turns out this problem has been around since 2006 with Trane and American Standard Hi-Efficiency furnaces.  The source is the fan inducer motor - they went to a new design of the motor they used.  It generates strong RFI (S9 levels) from the broadcast band all the way up through VHF and UHF - wipes out AM radios, TVs, routers, etc.
> 
>Trane is apparently aware of the problem.  They have a shielded cabling kit that can replace the inducer motor wiring harness which acts like an antenna.  
> 
>I called the servicing dealer and the "technical expert" phone rep I talked to was clueless.  After I told her the exact problem, the source of the problem and the factory fix for the problem (with part numbers) - with her taking notes - she put me on hold.  She came back online after talking to someone to tell me "yes, there was a wiring kit that they could install but it may or may not eliminate the problem."  
> 
>>From what I researched, it appears that the shielded harness sometimes solves the problem and sometimes does not.  But from what I could tell from the posts I read, it looks like it really depends on what kind of RF ground is installed on the shielded harness and furnace and how complete the shielding is on the inducer harness that determines how effective the fix is.  If the installation of the shielded harness works the noise level has been reported to drop to minimal levels.  Right now the furnace has an electrical ground but no RF ground, so it appears I'm going to have to install one.
> 
>The dealer service manager is supposed to call me back and let me know what they can do for me.
> 
> 
>
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>
>-- Steve, K7PZN 
>"Think Quickly, Speak Slowly, Work Diligently, Live Simply"
>
>--- On Mon, 3/28/11, rbethman <rbethman at comcast.net> wrote:
>
>
>From: rbethman <rbethman at comcast.net>
>Subject: Re: [R-390] High Electrical hash noise level
>To: "Steve Toth" <stoth47 at yahoo.com>
>Date: Monday, March 28, 2011, 12:21 PM
>
>
>Holy crap!  Just like the GE J-79 in the F-4 Phantom!
>
>I'd start with the tech support through the dealer, and hint strongly about ferrite beads and the like.
>
>There HAS to be a method to get rid of it.  Perhaps an isolation transformer that feeds the burner?
>
>Thinking out loud.....
>
>Bob
>
>On 3/28/2011 3:13 PM, Steve Toth wrote: 
>
>
>
>
>
>Bob
>Just pulled out my battery operated WWV/weather receiver and turned up the thermostat on the furnace.  As soon as the burner/igniter kicked in it totally drowned out WWV on 5, 10 and 15Mhz and quit when the burner turned off.  So it looks like HF RF interference with the igniter acting like a broadband spark gap using the wiring as an antenna.
>
>
>
>
>
>
>
>
>-- Steve 
>"Think Quickly, Speak Slowly, Work Diligently, Live Simply"
>
>--- On Mon, 3/28/11, rbethman <rbethman at comcast.net> wrote:
>
>
>From: rbethman <rbethman at comcast.net>
>Subject: Re: [R-390] High Electrical hash noise level
>To: "Steve Toth" <stoth47 at yahoo.com>
>Date: Monday, March 28, 2011, 11:53 AM
>
>
>Steve,
>
>Damn shame that you are in WA and I'm here in VA.  I've got an HP-312 
>sitting here.  Works darn good too!
>
>One other idea.  Try a separate ground from the Trane furnace chassis to 
>the direct outside power ground.
>
>Also, pour water on the ground rod for the service entrance.
>
>Bob - N0DGN
>
>On 3/28/2011 2:39 PM, Steve Toth wrote:
>  
>
>>Bob
>>I'll have to find out if anyone (like maybe the Trane servicing dealer whom I think Trane is going to end up referring me to) has something equivalent to an HP-312.  The noise seems to be very broadband in nature though - no matter what frequency I have the R-390A tuned to, the hash just drowns out any signals, so I'm thinking it is electrical. 
>>   
>>At least with the suggestions so far I'll be able to determine if the noise is electrical in nature and just traveling through the wiring, or it's RF using the house wiring for an antenna.
>>   
>>If it turns out to be very broad band RF(which is possible since it has to do with the igniter in the furnace and could be acting like an old spark gap transmitter with no tuned circuit), I was looking around on the web this weekend and came across the Timewave ACN-4 Noise Canceller - it picks up noise on it's own antenna, shifts it 180 degrees out of phase, then combines it with the original noise to eliminate it.  The article I read by a ham who installed one was favorable.  It's one possible idea if it turns out filtering won't work.
>>
>>
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>>-- Steve
>>"Think Quickly, Speak Slowly, Work Diligently, Live Simply"
>>
>>--- On Mon, 3/28/11, rbethman<rbethman at comcast.net>  wrote:
>>
>>
>>From: rbethman<rbethman at comcast.net>
>>Subject: Re: [R-390] High Electrical hash noise level
>>To: r-390 at mailman.qth.net
>>Cc: "Steve Toth"<stoth47 at yahoo.com>
>>Date: Monday, March 28, 2011, 11:21 AM
>>
>>
>>Steve,
>>
>>The reason for suggesting something like an HP-312, is you "may" be able to locate a "high concentration" of the hash in a "band" of frequencies.
>>
>>That would at "least" give you a chance to build a blocking filter.
>>
>>It comes down to "Been there, done that.  No T-shirt!".
>>
>>All I managed was a WHOLE stack of dirty words!  LOL!
>>
>>Bob - N0DGN
>>
>>On 3/28/2011 2:15 PM, Steve Toth wrote:
>>    
>>
>>>Bob
>>>Step one completed - emailed Trane via their website.  We'll see what they come back with.
>>>     I'll pull out my Radio Snack WWV radio and sniff around the furnace and electrical Panel.
>>>I'll also try the short piece of wire on the antenna connection; and check the line with the oscope to see what I've got.  Good ideas, thanks.
>>>
>>>-- Steve
>>>      
>>>
>>
>>
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>>
>
>  
>
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