One additional comment on air source heat pumps. I just had a Bryant
Evolution Extreme (same as Carrier Infinity) installed which has a VFD
compressor. I was concerned about RFI of course. They offer an RFI kit
that goes between the unit and the A/C line which I had installed as
part of the deal.
The installer was a home energy performance guy, not your typical slam
and run HVAC dealer, so he was interested enough to take the time and do
some testing with me. His grandfather was a ham :-).
Even without the RFI kit, I did not hear any noise from the unit but we
installed it anyway since he got the distributor to throw it in. None of
the ECM fan motors make any noise either. Overall a great unit RFI wise
and performance wise. It's amazingly quiet in the audible range too.
A couple additional "just in case" measures during install:
1. Pulled shielded, twisted pair control cable between the T-stat, air
handler and outside unit. These new systems are "communicating" and only
use two wires and a proprietary serial protocol. I can dig up the Belden
part number if anyone is interested.
2. Put all electrical in metal conduit.
Reduced our cooling bill to ~$100/month during 2 of the hottest months
on record in the foothills of the Sierra.
No, I don't work for Carrier/Bryant. Just very impressed with this
technology. Not your fathers HVAC. Do find a dealer that understands
these systems. We had some teething pains as I was the first install in
this area, but it all got done right in the end.
73,
Steve
W1SRD
This is just a total shot in the dark but do they have an air source
heat pump which was installed within the last few years? Sometimes
these are called ductless AC units. The newer models use PWM to drive
the compressor. The variable speed drive which PWM allows makes the
units much more efficient (they can run more or less continuously
instead of all on or all off) but PWM is, of course, full of
harmonics. The unit I had recently installed is below the noise floor
at my antennas but I can see poorly filtered models being a real
problem for radio amateurs. If they had an air source heat pump
installed, you should see the compressor on the exterior of the house.
It will look something like this:
https://www.goductless.com/hvac/images/mitsubishi/PC19508-d.jpg
If you live in a climate where you get more than a few inches of snow
in one storm, the compressor will likely be wall hung 4'-8' off the
ground. Otherwise, it will be on a plastic or concrete pad.
Again, just a shot in the dark. Seems like a possibility considering
it's more or less continuous during cold weather.
-Jeff
W7WWA
On Mon, Sep 23, 2013 at 9:58 AM, Gary Tuck <gtuck@mac.com> wrote:
Last winter I had almost steady RFI most every day, most hours of the day. It
seemed to begin when new neighbors moved in next door. As the weather warmed
in the spring, the RFI disappeared. Then the neighbors moved and I had hope
they took the noise source with them. They are gone but the weather cooled
yesterday and the noise is back. The house is vacant. So, now I have to get
serious. The only sources I've had in the past are power line noise and
defective lights. I've tried turning off every circuit in the house last
winter and I'm convinced it isn't within our home. It's steady, raspy but not
sputtering. I was assuming that it is a portable heater of some kind but what
common sources are there related to cold weather? What might I be looking for?
Thank you!
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