Trane furnace radio/TV interference

[modelman]

Several months ago I had a high efficiency Trane XV90 natural gas furnace and heat pump installed. Since the weather has recently been cold enough for the gas furnace to provide heat, I have been experiencing severe radio interference. The interference wipes out AM broadcast reception throughout my house. I also see snow on a TV connected to an external antenna.

The radio noise occurs as soon as the draft inducer motor starts up; the pitch of the interference is related to the motor speed. The draft inducer motor is a dc motor driven by a PWM controller on the main circuit board. It is well known that PWM systems generate strong harmonics throughout the radio spectrum, resulting in radio interference. However, properly designed PWM systems include filtering and shielding to suppress the radio frequency currents from the wiring.

I contacted my installer, who is totally unfamiliar with the problem. The electrician who was sent to my house to investigate the problem also doesn't understand what's going on. I had to explain the difference between an RF ground and dc or house ground to him. Although everything appears to be well grounded from a dc perspective, I suspect that portions of the system are radiating RF energy.

Several days ago I emailed Trane about the problem, but haven't received any response.

Although there has been past discussion in this group about radio/TV interference emanating from Trane high efficiency gas furnaces, I haven't seen any definitive fix. Does anyone know if Trane has a fix for this problem. Do they have a shielded cable and or rf filter kit to suppress this noise? Since my system is under warranty, I won't attempt any modiifcations to the system.

Has anyone experienced this problem?

Thanks.

[Tony Hwang]

Hi, First you'll have to find out whether the interference is coming thru the power line or thru the air. It can be cured but needs some expert knowledge. Maybe Trane has noise suppressor kit of sort? Better check with them. Tony, VE6CGX

[buffalobill]

[buffalobill]

[modelman]

Tony,

The interference is being radiated, since I can hear it loud and clear on a "walkman" outside of my house. I haven't yet determined which wiring (power line to the furnace, thermostat cables, etc) is doing most of the radiating. When I "sniff" the wires with my walkman radio, everything seems to be hot with the rf interference. There is no significant change in intensity with split core ferrites (type 31 ferrite) on the thermostat cable. I haven't yet tried an EMI filter in series with the ac line to the furnace. That would require some work on my part, and I want to give Trane a chance to solve this problem.

Yesterday I questioned the electrician about why the furnace ground is connected to the gas pipe; I didn't get a logical answer. He said that is the way it's done on all installations. I pointed out that the gas pipe is bonded to the electrical ground of the house and water pipes at its far end about 25 feet from the furnace, providing a dc ground but not an rf ground. I suspect that the gas pipe may be acting as an antenna. However, there was no change in interference when the ground is lifted from the gas pipe. A short ground connection to a ground rod may provide a better rf ground for the furnace.

The outfit who installed my furnace promised to contact Trane today. I hope to know more shortly about what solution Trane proposes.

Thanks.

Jack, K1VT

T> > Several months ago I had a high efficiency Trane XV90 natural gas

[MLD]

"modelman" wrote in message news: [e-mail]...

Here's one guy that had the exact same problem. I was a bit luckier that you in that it didn't bother my AM radio signal but it did screw up my kitchen TV picture--rabbit ears. It's coming from the inducer motor as you surmised. The installer was very cooperative and tried to fix it based on input from Trane. Changed out the cable to the motor with one that was supposed to provide better shielding and when that didn't work changed the control board---both without any success. Prior to and after component replacements I tried grounding everything that I could, again with no success. Got the local Trane Rep on the phone; he made promises but never followed through with a solution. Had a new Trane for about a year that got into a problem resulting in it being replaced under warranty rather than repaired--it was the replacement furnace that had the RF noise problem. Found out that Trane went to a "new design" inducer motor. I tried to get the Trane Rep to replace the motor with the same design that was on my first furnace. No luck there, was just ignored and yessed to death. If Trane acts dumb about the RF noise it's all show-because mine happened about a year ago. My guess is that you're stuck with the problem. I finally made mine going away by putting in a cable line to the TV. My suggestion in your tussle with Trane or the installer is to go find an inducer motor from an earlier vintage furnace. Even if it has to be cannibalized off an older (2yrs or so) furnace. MLD

[MLD]

Looking back, I now recall that replacing the inducer motor wiring harness with one that had better shielding did make a significant improvement although it didn't completely resolve the noise problem. MLD

[Smarty]

This comment opens up the possibility that wrapping the existing harness with a braided wrap as a helix and then bonding the outer braid to a good earth ground may help the radiated electromagnetic interference (EMI). The conducted noise will still need to be filtered / trapped before the wiring enters / exists the furnace. Given that this EMI goes from the AM band (approx 1 MHz frequency all the way up to VHF or UHF television frequencies, however, the likelihood of being able to devise a good wideband filter which substantially reduces the conducted EMI is remote without a lot of expense. If the motor itself is truly the principal noise source, then getting some noise suppression right at the motor offers the best solution, either with shielding, series inductors (chokes), shunt capacitors, or all of the above. The motor brushes and commutating connections may be creating a lot of arcing, and a new motor may help if it is constructed differently (from a different vendor).

Smarty

"MLD" wrote in message news:d6J4h.3603$Ue.2593@trndny03...

[MLD]

Just to remake the point---the problem is, without question, the inducer motor. The "new shielded" harness put in my furnace still had, in my opinion, a major flaw. The wires at both connector ends was unshielded for approx 1 inch. So all the wires, at both ends, was exposed to picking up and/or radiating any RF noise. I shielded, using foil, the exposed wires, grounded the harness shielding to the furnace, my earth ground, water pipe and control board grounds. Nothing got rid of the noise problem. You offer some potential fixes but its apparent that Trane isn't interested in putting any effort into resolving the issue. MLD

frequencies,

perspective,

[modelman]

MLD

Interesting that your problem was with the motor itself and not the PWM circuitry. My first thought was that the fast switching of the PWM generates strong high frequency components. I note that the whine (modulation on the noise) varies varies with the motor speed.

My furnace is only about 4 months old and is also under the 10 year extended warranty (offered as a promotion), so I don't want to mess with my own shielding. If Trane doesn't provide a fix, I will continue experimenting with split core ferrites on various wires. I haven't tried putting ferrittes on the wiring to the motor.

S> > Several months ago I had a high efficiency Trane XV90 natural gas

[modelman]

The retrofitted grounded helical shield may be effective if the windings on the helix are bridged; the shield needs to provide a low impedance for the noise. Otherwise, the noise current would be forced to follow, and be impeded by, the windings of the helix, which is simply an inductor.

If Trane doesn't have a solution within a reasonable amount of time, I may experiment with such shielding. It would take some very careful soldering to bridge the windings without damaging the insulation on the enclosed wires.

I may also try using some very light guage copper sheet (or foil) folded around the wiring harness and closed with screws and nuts. That way I wouldn't have to worry about soldering and bridging the turns on the helix.

Any other ideas?

Smarty wrote:

[Smarty]

Given Trane's attitude and the fact that you have localized the problem to originate at the induction blower, I would replace the motor leaving the existing associated parts intact if possible (impeller / squirrel cage / overtemp thermostat, etc) or replace the entire assembly which includes the motor and associated parts entirely. Having replaced two of these myself, I know this is likely to be a $175 item or more. Adding EMI filtering requires more measurement and experimentation than most people are willing to try, IMHO, so I am reluctant to suggest designing your own EMI filter by trial and error. Wrapping some foil around the blower housing (being careful to avoid shorting out any attached thermostats / safety switches / may help if the motor itself is radiating (as opposed to conduction out through the wiring harness).

Smarty

[m Ransley]

Take Trane to small claims if they dont fix it. After they are served it will be fixed in a week.

[Tony Hwang]

Hi, That sounds like a toughie. Hope everything is tight as far as terminals and connections go on the control board. Random noise emission is hardest to get rid of. Reminds me of noise blankers on our receivers, hi. My furnace is Carrier and did not enoucouter any problem. I assume FM radio is not affected.

73, Tony, VE6CGX

[Tony Hwang]

Hi, If that's the case, FCC may be interested. Have you reported to FCC?

[m Ransley]

If you file in small claims for the nominal fee, [mine is 35$] Do you really think Trane will fly in an atty for a day at considerable cost and possibly loose 3000 and make local new hurting sales, or get your furnace fixed. I think they will fix it within 30 days. If they see your attemps to alter it you are screwed. Start by a certified letter and many emails to Trane and print copies. Video your interference issues-tests.

Maybe different organizations like FTC, FCC, CPSC, Consumer Reports, etc can guide you on other complaints. This issue is not new.

RF I would think is regulated. Excessive amounts have to be of concern of saftey for medical, security, and other equipment. Even if Trane has figured a legal Out with the FCC, your local judge wont like it not will Trane want to pay to go to court .

[modelman]

Got a call from a Trane rep who contacted my local distributor and scheduled to install a shielded cable harness between the PWM control board and the motor. The work is scheduled for Tuesday. The Trane rep claims that they are aware of the problem and that the shielded cable eliminates the noise. Figure I'll give it a shot and take it from there.

By the way, MLD reported earlier that he had that d> If you file in small claims for the nominal fee, [mine is 35$] Do you

[Zibs]

Modelman:

Please keep me informed on this problem. I also recently had a Trane xv90 installed and am having the same rf interference problem. The local installer hasn't got a clue, so I phoned Trane, who is supposedly going to contact and advise them

zibs

modelman wrote:

[Zibs]

Modelman:

Please keep me informed on this problem. I also recently had a Trane xv90 installed and am having the same rf interference problem. The local installer hasn't got a clue, so I phoned Trane, who is supposedly going to contact and advise them

zibs

modelman wrote:

[BT]

Modelman,

I have an American Standard two stage variable speed furnace and have the exact same problem. American Standard owns Trane and furnaces by either brand name are exactly the same, with the exception of the first letter of the model number and the label on the door. In other words, the Trane XV is the same as the American Standard Comfort-R.

I'm guessing that your furnace model number begins with TUY.

I tried to have the dealer resolve the problem without success. I had consulted with the regional distributor who claimed that there was a main board replacement fix. The dealer replaced the board under warranty. There was no change. For other reasons, the furnace was replaced. The new furnace, built a year later, has the exact same problem.

My noise sounds the same as you, starts when the inducer motor starts (before the blower fan comes on) and shuts off when the inducer fan shuts off (as soon as the thermostat stops calling for heat.) When the inducer fan increases in speed, the interference changes in pitch and may get louder.

The interference is enough that I can pick it up outside the house while listening to a strong nearby Class A radio station.

I recently saw a post on

that mentioned that Trane/American Standard now has a fix that involves shielding the inducer fan wiring. This may be the same thing that MLD reported and you mention above. Please report back what you experience, I plan to call for service too very soon, while I'm still under warranty.

While American Standard brand and Trane brand are the same, they have different wholesale distributor networks, so if one fails to help, perhaps asking the American Standard distributor for your region could at least have a clue, not sure. One thing that I am sure about is that calling the manufacturer is frustrating. At best, you just get redirected to call your local distributor. When I was having problems with my dealer, the manufacturer rep admitted that anyone who is locally licensed can be an American Standard HVAC dealer, they really don't care. I believe they might more tightly control the Trane brand dealers, but who knows.

You can try calling the manufacturer anyway at 888-556-0125. I would do this just to register your radio interference issue, in addition to complaining to FCC. Hopefully if enough of us do this, the problem will someday be resolved.