[RFI] Heat Pumps RFI

[Jim Brown]

On 5/30/2023 1:27 PM, Gene Smar via RFI wrote:
 > I'm replacing our heat pump with a building code-compliant model: 
Bryant FV4CNF002 indoor air handler, Bryant 215SAN024003 (2) ton heat 
pump.  Has anyone had experience, good or bad, RFI-wise, with this 
model, or with Bryant in general?

Hi Gene,

Look for anything in the operating characteristics indicating VARIABLE 
speed (as opposed to two-three speeds that can be selected). 
Variable-speed motors are generally noisy (because they're varying the 
width or frequency of rectangular wave trains that drive the motors, 
which can be big current).

There's much more than that to it -- because the motor drive circuit is 
NOT DC, it's DC plus RF, it MUST be treated as a transmission line, not 
as a DC circuit, to prevent radiation of noise. And there are other 
issues, like the capacitance in filters between neutral and ground can 
cause division of RF return current between neutral and multiple ground 
paths. This causes phase (Hot) and neutral (return) currents to be 
unequal, which defeats cancellation of the fields, increasing radiation 
and the magnetic field produced (which dominates in the near field).

73, Jim K9YC