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Author Topic: RFI from gas line?  (Read 3759 times)
KC1BMD
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Posts: 316




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« on: March 21, 2016, 10:49:02 AM »

I have RFI from our Trane XV90 furnace when it switches on. I had their RFI kit installed (TRANE KIT14668) supposedly to cure RFI problem due to the draft inducer motor, but that didn't seem to help. I was sniffing around with a portable AMFM/Shortwave radio (also covers ham bands) trying to identify other possibilities to lower my noise floor and found a lot of hash across the AM band near the natural gas line supplying the furnace. This is with the furnace having power applied but not on. I have no clue if this is causing noise in my iCOM radio or not yet but has anyone ever heard about (or observed this) before?

Also found this post but nothing conclusive. I don't believe my meter (~8 year old condo) has any RF transmission capability but will need to verify:
http://www.eham.net/ehamforum/smf/index.php?topic=77650.0
« Last Edit: March 21, 2016, 03:36:52 PM by KC1BMD » Logged
KC2MMI
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« Reply #1 on: March 21, 2016, 01:02:49 PM »

IIRC there are also some water meters that are using some type of remote transmitter, so the water guy can read them from the curb the same way. A little box half the size of a cigarette pack, mounted externally on the home, and connected to the meter.

FWIW.
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KC1BMD
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« Reply #2 on: March 21, 2016, 01:13:02 PM »

You're right about the water meter! It was converted over to the remote read type before we moved in. Now, how do I test it? Shocked
I don't think it explains the apparent emissions from the gas line but I need to consider all sources.
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KD0REQ
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« Reply #3 on: March 21, 2016, 01:55:13 PM »

check your building codes.  if permitted, bond all utility pipes around that furnace (in most homes, the furnace room is also the water/sewer entry point) with at least 6 gauge copper using the appropriate clamps to a secure electrical ground. "appropriate clamps" means do not create any possible electrolytic corrosion using the wrong metals.

if there is plastic water piping or gas piping inside, or flex gas line, don't even try this.  don't even think about it.  block me online.  block yourself online.  it won't do any good, and may do something seriously dangerous.  seriously.

if you happen to have a combination heating outfit, one that also does plumbing and electrical work, have them evaluate if it's a safe move.  we have a number of them in the Twin Cities.  their tech group would be able to determine if this is (1) safe and (2) effective in very short order.  in olden times of yore, there would also be a line to the effect of "bond around the gas meter" but there aren't steel lines used any more.  wasted effort as well as a slight physical damage to the line from the bond clamps.  go there not, grasshopper.
« Last Edit: March 21, 2016, 02:01:10 PM by KD0REQ » Logged
WB4SPT
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« Reply #4 on: March 21, 2016, 02:09:14 PM »

You're right about the water meter! It was converted over to the remote read type before we moved in. Now, how do I test it? Shocked
I don't think it explains the apparent emissions from the gas line but I need to consider all sources.

I've got the same model furnace, and I and others have written up successful reports.  So, let's get you out of the weeds.  Step 1:  turn off the power to the furnace.  Does the interference go away?  The inducer drive system in these furnaces DOES cause EMI on the HF bands.  There should be a nearby toggle switch to kill power. 
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KC1BMD
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« Reply #5 on: March 21, 2016, 02:46:10 PM »

I know when the furnace kicks on that it raises the noise level several S-units. The Trane kit did not solve it (and I believe there are some others it did not help). That noise disappears when the furnace is not calling for heat. This noise does not occur when only the blower motor (moving hot air through the ducts to the living space) is running, but only when the inducer fan motor kicks in which pushes exhaust out.

The other noise I was questioning (the subject of this thread) is the apparent broadband noise I hear on AM/FM/Shortwave radio when it is held near the solid metal gas pipe (not flex line) and I do not suspect it is coming from the furnace since this noise does not change whether the furnace calls for heat or not.
« Last Edit: March 21, 2016, 03:40:54 PM by KC1BMD » Logged
WB4SPT
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« Reply #6 on: March 21, 2016, 04:06:49 PM »

W8WRP did a nice write-up on the XV95, a similar furnace.  He actually did bond the gas pipe to the furnace frame.  I did not, but these things are not exactly cut and dry.  Also, there is a processor running on the board, and it's powered before any call for heat.  I would encourage you to power off the furnace to completely remove it as a possible RF source.  good luck.
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KC1BMD
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« Reply #7 on: March 21, 2016, 05:17:14 PM »

W8WRP did a nice write-up on the XV95, a similar furnace.  He actually did bond the gas pipe to the furnace frame.  I did not, but these things are not exactly cut and dry.  Also, there is a processor running on the board, and it's powered before any call for heat.  I would encourage you to power off the furnace to completely remove it as a possible RF source.  good luck.
Thanks, I saw that write up and downloaded the pdf file. I tried to contact all three of the people listed on the first page as contributing to that document using contact information in that document (as well as QRZ info) and I got no response. I guess I have some further investigation to do.
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KD5PKS
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« Reply #8 on: March 24, 2016, 06:50:47 AM »

I know when the furnace kicks on that it raises the noise level several S-units. The Trane kit did not solve it (and I believe there are some others it did not help). That noise disappears when the furnace is not calling for heat. This noise does not occur when only the blower motor (moving hot air through the ducts to the living space) is running, but only when the inducer fan motor kicks in which pushes exhaust out.

The other noise I was questioning (the subject of this thread) is the apparent broadband noise I hear on AM/FM/Shortwave radio when it is held near the solid metal gas pipe (not flex line) and I do not suspect it is coming from the furnace since this noise does not change whether the furnace calls for heat or not.

The gas meter probably has a remote transmitter like the water meter. I have seen these cause interference at wireless frequencies and the gas companies have also repaired when notified about it. The transmitter on my meter is behind the meter movement and has no external antennas or other obvious indicators except that the meter movement housing is deeper than the older one and plastic.
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KC1BMD
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« Reply #9 on: March 29, 2016, 10:28:28 AM »

Draft inducer fan motor noise (Trane XV90): This is obvious. It starts and stops with the motor coming on. I have some more work to do to see if I can enhance the kit they installed for that (Trane KIT14668), maybe by adding some additional ferrites, re-routing cables, etc.

Broadband noise: Higher on 40m (S4-5), a bit lower on 20m (S3-4). This noise appears to be across the entire band with no periodicity to it.
- I shut power off to furnace -> no change.
- I have yet to shut my power off (individual breakers, etc) but will be doing that to try to isolate further.

Meanwhile, I found out that all three of my meters (gas, electric and water) have transmitters allowing the utilities to read remotely (I assume from a truck). I don't know what type of noise these would produce but if any of these are the source, I'm not sure what I could do about it. I'm trying to determine if the utilities have some way to temporarily deactivate them, which would make for easier troubleshooting.

This will take time to get some improvement, if I can at all... so I need to get prepared for the long haul. Sad
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KC1BMD
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« Reply #10 on: March 30, 2016, 06:05:39 AM »

Water Meter: Has remote read capability (~1/8 - 1/4 mi range) and uses frequency hopping in 902 -928 MHz range. Output every 10-15 sec for .02 sec duration. So I doubt this is a noise source in my case, since I would see some type of periodic pulse type noise, rather than broad elevated noise/hash at no specific frequency which is what I see.
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