Variable Speed HVAC- Any Problems? - RFI Forum at eHam.net

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eHam.net Forum : RFI : Variable Speed HVAC- Any Problems?

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Variable Speed HVAC- Any Problems?	Reply
by K3AN on December 6, 2006	Mail this to a friend!
We will be replacing our heat pump system shortly, and two dealers are proposing high-efficiency, microprocessor-controlled, variable speed air handlers to better handle the high summer humidity. Have any of you experienced noticeable RF interference from a new HVAC system, either your own or perhaps the next-door neighbor's new unit? If so, what brand? Many thanks. Bill, K3AN

RE: Variable Speed HVAC- Any Problems?	Reply
by K3AN on December 6, 2006	Mail this to a friend!
Adding to my own post, I just looked at the furnace RFI post below. Trane is one of the brands we're considering. But ours will be a heat pump with electric resistance back-up heating, not a gas furnace. It's heat pump/air conditioning interference I'm interested in hearing about. Thanks again.

RE: Variable Speed HVAC- Any Problems?	Reply
by KE2SI on December 8, 2006	Mail this to a friend!
I have a TRANE XV90 that is new with our newly constructed home. The XV90 has a variable speed DC fan and is touted as a 94% plus efficiency. All was OK until I hooked up the HF station at the house and found that all hell breaks loose with the noise floor when the furnace turned on. I spoke with the local distributor and he was not aware of any RFI problems with the newer XV90s stating that proper Circuit Board decoupling had been added. I managed without his help to find some fixes that dropped the noise floor to near impersception. It involved adding ferrite to both the thermostat cable and the AC power lines. I would not buy this furnace if I knew what I know now.

RE: Variable Speed HVAC- Any Problems?	Reply
by N5AX on December 10, 2006	Mail this to a friend!
Bill, I've had a new Trane variable HVAC for 4 months. It has no RFI at all on my IC-756 Pro3. 73 Hil, N5AX

RE: Variable Speed HVAC- Any Problems?	Reply
by WT4T on December 13, 2006	Mail this to a friend!
Ive been in the hvac business for 40 years. there are only two mfg's of vari speed drives,emerson and ge. All of the manufactures use one or the other. They are both based on a dc drive system. I have the ge at home ,never a problem of any kind. The emerson drive does cause some hf noise problems,easily fixed with a few torrids here and there,mostly on the leads from the controller to the motor. Both GE and EMERSON WILL HELP YOU OUT,if you contact them directly. They have all the answers,where the furnace mfg...train,carrier,rheem etcreally arn't much help.. go direct to the mfg.of the drive. dale wt4t

RE: Variable Speed HVAC- Any Problems?	Reply
by KE2SI on December 14, 2006	Mail this to a friend!
Dale, Thanks a bunch for the advice! I do have an emerson board in my furnace. I have shielded the motor wires and placed torroids on the power lines entering the furnace. In addition, I have placed some clamp-on ferrite beads on the thermostat lines. I have reduced the interference significantly with these fixes - to the point where it is no longer across the entire hf band, but segments that are luckily not in the amateur bands. In sniffing with my small radio, I have noticed that the gas line (propane) has some rf on it and I believe that this is looping with some of the other gas appliances. My next fix will be to run a dedicated ground along the gas line with the aim of shorting the loops. My noise problem seems to subside when the burner actually shuts off, so I believe that the motor servo is no longer the culprit. Do you know if the gas valve servos as well? If so, I think that will be my future focus. Regards, Paul, KE2SI

RE: Variable Speed HVAC- Any Problems?	Reply
by K3AN on December 19, 2006	Mail this to a friend!
Thanks for the replies. We'll be getting a Trane system installed in early January. Variable speed air handler but single-speed compressor/condenser. Will post with my test results afterwards.

RE: Variable Speed HVAC- Any Problems?	Reply
by N0GBR on December 22, 2006	Mail this to a friend!
This year I've had 2 Tane A/Cs and 2 Trane furnaces. The ONLY one with a problem is the XV90 Trane furnace unit. Wipes out all communicarions below 30 mHZ. The dealer says he can't figure it out but it has been helpful to point out that others here have had problems too. He says he's talking to the rep but I've also complained to the national co. Other than the rfi I'm happy with the A/C and furnace efficiency (my electic bil was HALF what it was with my 22 yr old A/A it replaced)

RE: Variable Speed HVAC- Any Problems?	Reply
by N0GBR on December 27, 2006	Mail this to a friend!
Trane is installing an upgrade to fix this issue, I'm told, today. The rep says my unit is the first nationally to have this fix on the XV90. I will let all know if this does it!

RE: Variable Speed HVAC- Any Problems?	Reply
by N0GBR on December 27, 2006	Mail this to a friend!
With two repairmen here today new RFI filter installed into the Trane XV90 but it had no effect on HF RFI. They finally decided it was the variable speed "blower" not the circulation fan nor the board that is the problem. They'll be back again next week... fifth time for this issue. At least they are diligent in their pusuit!

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