David:
Thank you for the reply.
My spectrum analyzer is a Tektronix 7L12. Although the lower
Frequency limit is DC, it is difficult to resolve meaningful signals
At very low frequencies due to the Zero marker leak thru masking
Any signals.
I will say that at HF frequencies above 3 MHz below 8 MHz is where most
Of the RFI is showing up. Using the spectrum analyzer in zero span mode
There is a very complex switching waveform which is hard to separate out
any 6500 Hz components. Viewing the spectrum it occupies the above
frequency
range. Below about 3 MHz there is very little energy showing. The AM
broadcast
Band is not affected at all.
Using some basic DF techniques I am pretty sure that the source is the
inverter
driving the compressor motor.
Just to clarify. The COMPRESSOR motor is a three phase motor as shown in
the
Rheem documentation. It is not self contained ECM motor, nor is it a
capacitor
Start type motor. It is truly a three phase motor. I have not had the
external
Metal surrounding all of the outside electronics off just yet, as I don't
want to
Go too far down the rabbit hole with regard to voiding any warranty.
I thought posting to this list might show another user with similar issues
with a
similar unit. I suspect there will be several solutions applied in the
final accounting
to solve this issue.
Right now the installers used the original un-shielded control wiring from
the inside
Thermostat to the outside electronics. One part of the solution may be
having to
Replace the un-shielded control wiring with shielded control wiring.
This system is sort of a state of the art control system, as it uses what
Rheem calls
ECONET. The thermostat does not send a solid control signal generated by a
closed
Or open relay in the thermostat. It uses a binary data stream coming from
the Thermostat
to the outside compressor unit and also the Air handler in the attic. Sort
of like a CAN bus
communication system. I'm not sure what the protocol and physical layer
component are.
I am speculating at this point, but this may be as simple as re-routing some
of the internal
Wiring in the outside unit to prevent coupling of the high power switching
components from
being coupled on to low voltage wiring. One cannot simply put a low pass
filter on the data
Lines coming from the thermostat as it would kill the waveform logic high
and low.
Common mode choke would be good here. When they installed the new unit
they
Took off a common mode choke I had installed on the old thermostat control
wiring at the
outside unit. The installers did not leave enough slack in the control
cable to install another
Choke.
Plus one other horrible thought. If the high voltage inverter switching
signals are coupling to
The actual high side and low side Freon copper piping that presents a
difficult problem to solve.
Right now I'm just familiarizing myself with the system components. So that
I can drag
The scope and current probes outside and do some more measurements.
Karin Anne Johnson P.E. K3UU
Palm Harbor, FL
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|