Aside from being in agreement
It's shocking that it would radiate as bad as 20 acre's WOW-- you would
think something that bad would be illegal , isn't it??
as an aside to my earlier email, forgot to mention those magnatek600
controllers have also wiped out some tenants cordless phones and
am/fm radios
it's amazing such a wide band multi band interference producing device
can be allowed to be sold
They too had a 'filter kit ' naturally for sale thou it should be free
(guess this can also be a small profit center for them ) which was
essentially a filter for the ac input, however no interference was
on the that point ironic
73's
On Apr 10, 2010, at 4:28 PM, W2RU - Bud Hippisley wrote:
>
> On Apr 10, 2010, at 4:06 PM, kd4e wrote:
>
>> Warning: Many of the new HVAC systems are promoting
>> variable-speed motors in their design - it is one way
>> that they increase the "magic" SEER.
>
>
> The York "Affinity 3S" heat pump system has just such a beast in it.
> Wherever you see reference in their literature to a "variable speed air
> handler", you know you're dealing with a PWM RFI generator.
>
> Recently I had occasion to check the RFI environment around a home with one
> of these in it. The installation was between two and three years old and had
> been done by a reputable heating/cooling firm.
>
> The RF noise from this system totally wiped out my mobile installation
> (TS-480 with a simple Hustler mast / resonator antenna) on at least 80, 40,
> and 20, both in the driveway and for at least a quarter mile in each
> direction on the road in front of the house. Similarly, it totally "trashed"
> reception on my Radio Shack all-wave portable from the broadcast band up
> through 160 meters and beyond, and it was audible no matter where I carried
> that receiver on the 20-acre property. By far the biggest amplitudes were
> found at the thermostat on an interior wall of the main floor and on the
> power / control wiring at the compressor outdoors, but there was more than
> enough hash near _all_ the power wiring in the house to mess up ham radio
> reception on any antenna on the property and for some distance beyond.
> Interestingly, the air handler chassis itself, which was located in an attic
> area one floor above the thermostat and not more than 25 feet away, was
> relatively "quiet".
>
> We ran four cycles of turning the system on and off to be absolutely certain
> that it was the source of the noise. As the fan powered down each time, you
> could hear the PWM waveform change on my mobile rig, just before the fan shut
> off each time.
>
> Interestingly, the house had two heat pump systems -- the Affinity 3S, which
> handled the heating / cooling for a 2-year-old addition, and another one,
> pre-PWM, that handled the original (10-year-old) section of the house. We
> cycled the old heat pump, too, and found it to be absolutely quiet except for
> a single RF "click" when it turned on, which had been my experience in the
> 1980s when I lived in a heat pump home of my own.
>
> We contacted the dealer that installed the Affinity 3S system, and he knew
> nothing about RFI from variable speed motors but he said he would check with
> York. I received a call back the very next morning; York knows all about the
> RFI problem and has an RFI Kit for their variable speed units. Installed by
> the local dealer, it would have cost around $250, plus the cost of
> 8-conductor shielded wire (!) to run between the hi-tech thermostat and the
> air handler chassis in the attic. Of course, we don't know how effective any
> retrofit kit might be, since it's clear to me (who used to design PWM power
> circuits for a living) that no particular effort appears to have been made to
> isolate the high transient currents in the motor drive circuitry from other
> circuitry and leads going in and out of the chassis, or to keep the PWM
> current loop area small.
>
> Give York credit for instantly responding with information about their RFI
> Kit (which, by the way, is a stock item in their Oklahoma facility), but
> wouldn't it be nicer if a little more time and pennies had been put into
> minimizing the loop areas and doing some other prudent avoidance engineering
> in the first place. Locking the barn after the horse is out does not usually
> lead to a fully satisfactory outcome.
>
> Bud, W2RU
>
>
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