In my _opinion_ you have a much smaller chance of a RFI problem if you
choose a machine with an AC motor. They are getting harder to find
and I'm told will be unavailable eventually because the U.S. Gov't
wants to increase the efficiency requirement of furnaces to greater
than 80% which pretty much mandates a DC variable speed motor. It
doesn't matter that there are vast amounts of natural gas now
available.
Also, high efficiency furnaces have fragile heat exchangers which will
fail. Most are made with stamped and crimped steel coated with
aluminum ("aluminized"). The aluminum eventually corrodes away in
spots leaving exposed steel to rust.
What about stainless steel?
You can get a s.s. heat exchanger if you are persistent and through.
They are uncommon because their heat transfer is much poorer and this
makes them unattractive to uninformed consumers and probably the EPA.
But if the free market were allowed to operate without meddling, most
people would probably choose 98% efficiency furnaces anyway, leaving a
few models available to people like hams who want longer life and an
AC motor.
The days of those 1/4 inch thick cast heat exchangers that lasted for
50 or 60 years are over because they resulted in efficiencies of at
most 50%.
My AC furnace is about 2 feet from where I sit in my ham shack. My
antennas are around 40 feet overhead. NO RFI.
73
Rob
K5UJ
>When I replace two air handlers in my house this year, is the general rule
>for minimizing RFI to make sure the motors are AC and not DC?
>73,
>N2TK, Tony
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