Furnace blower RF hash

[Ed-VA3ES]

Jim, W8WRP  has been extremely helpful in providing a virtual Trane XV95 RFI mitigation manual.  I can send the information electronically to anyone who requests it. It's a huge file, (7.4 Mb).

The furnace installation people are coming by tomorrow to install the Trane RFI kit. Jim's instructions  are far more intensive than what Trane provides. 

Most furnaces today use an ECM DC motor which is driven by a PDM pulse train. This PDM signal  propagates throughout the AC wiring, and control wiring.  The fix requires an big EMI filter at the AC input, and  ferrites on every control wire in and out. Some control cables must be shielded. I'm on nat gas, so the feeder pipe must be grounded too.  A big PITA.

I put together all of Jim's info into a bound manual, one of which I will keep with the furnace instructions, the other will be given to the furnace people.    If anyone is interested, I can be convinced to make copies for distribution.   It has all the RFI mitigation instructions,  12 photos, schematics and Trane's original RFI kit instructions.

If really  pressed, I could post the stuff here, but it would take  several postings to do a complete job.

[KD3CN]

Thanks for the info Ed,
Unfortunately my email would choke on a file that big.
Right now I' leaning toward getting an air handling unit with fixed speed fan.  The variable speed motor sounds like asking for trouble.  Perhaps I can still get a unit with relatively high efficiency.

I'd rather have pins in the eyes than volunarily put a big (expensive) RFI source in the shack.. 

Thanks,  Karl

[K3ZS]

I got a Trane heat pump a few years ago, however it is an add on to an oil hot air furnace.    The furnace blower has a two  speed blower, but it changes speed by changing the connections to it.    It makes no RFI at all.   The Tranes are good northern heatpumps.    The compressor and its fan are shielded (from lawn mower rocks) and the air exits on the side near the top, so you don't have to be clearing off ice and snow from the top of the compressor fan.    It provides heat down to about 10 degrees.    I have used 1/2 tank of oil since filling it up three years ago.   Just keep the thermostat up all of the time.   

[Jim, W5JO]

The Heil system I have is all electric and I can't follow the signal down the wiring anywhere.  It simply radiates from the cabinet.

One of the money saving parts of these systems is the variable speed motor.  If you wish to save on your bill, I would consider getting the variable speed system.  The RFI generated here is not that loud and I can hear stations over it, it's just annoying.  I am told a big core with the leads from controller board to the motor will do the trick.  My service man called the technical rep who first denied it was a problem but finally told him to get a "filter" from Radio Shack and wind the power and control leads and it would solve the problem.  My problem is I don't know which "filter" and he won't tell us. 

I think I may file a complaint with the FCC just to see what they will do, maybe they will get Heil to tell my what kind of "filter".  They have been such butts about this.

[ke7trp]

My "american standard" brand new HVAC system did this. RF chokes on the power leads fixed it. Its was the variable speed motor.

My philips HD DVD player is a lost cause. Plug it in to the wall with the power to the unit OFF and it puts out a nice 9S signal on every band. S9 +40 on the 6mhz band. No amount of filters fixed this. I just unplugged it.  When I want to watch a DVD we plug it in.

I was amazed at how much home devices put out hash on the ham bands. I have a small Sangean SW radio. I walked around the house with and found sources of noise to be the following:

ION type Air purifiers (we had two of them)
Kitchen lighting (FL type)
Carver stereo preamp.
HD DVD player was the worst.
Samsung HD TV but its livable.

With all that crap turned off my RX is nice.  Start switching stuff on and it gets worse and worse. When I talk on the AMI night, Its me with nothing turned on in a fairly dark house LOL



Clark

[k4kyv]

I think I may file a complaint with the FCC just to see what they will do, maybe they will get Heil to tell my what kind of "filter".  They have been such butts about this.

Yeah, just tell 'em to "go to Heil". 

I think one of the reasons so much consumer crap radiates garbage these days is that no-one listens to AM radio any more, except for maybe a few Rush Limpballs fans, and nearly everyone has cable TV.

I recently had a severe power line noise problem, and found the source about two miles away.  I knocked on a few doors in the vicinity, and found maybe a half dozen people home.  I asked them if they had been experiencing any radio or TV interference and let them listen to the portable radio I had with me.  The local AM BC station 8 miles away was nearly covered up by the sizzle.  Every single person I talked to told me no, they hadn't been aware of any problem, even though they were living right underneath the noise source.

A generation or two ago when most of the radio the public listened to was AM, and TV was picked up from a station 50 miles away with a rooftop antenna, this electromagnetic pollution would not have been tolerated.

If and whenever the great change-over to digital TV finally occurs, the situation will only get worse.

[Jim, W5JO]

My "american standard" brand new HVAC system did this. RF chokes on the power leads fixed it. Its was the variable speed motor.

Clark

Which power leads Clark, the ones to the motor or the ones to the unit itself?

[KD3CN]

Just wanted to post this info for others that might face a crapped-out heat pump.

The new unit is installed, with no rf hash problems on my receivers  (several feet away).
It is a Carrier FV4 air handler with variable (ECM) fan.  Before buying I rf-snooped a neighbor's FE4 air handler (also ECM variable fan), and heard nothing.  So I'd recommend either of these from an rf interference prospective. 

73!  Karl

[Opcom]

If you are clear in comunicating to the company trying to sell you this stuff they should be decent about it. In your case you already have it, so maybe a complaint to the FCC could help get someone's attention. You should not have to pay extra for them to fix this, nor do their engineering for them (possibly giving them a reason later to void your warranty). Hope it gets resolved soon.