Hello fellow RFI'ers:
Some time ago (probably over a year ago)I posted about RFI/EMI from a Rheem
HVAC unit, Model RP1748AJVCA. I've been very busy with other projects. Life
gets in the way sometimes.
Anyway, I've recently decided to tackle this issue again. And am doing some
more investigation. I can't definitively say that the RFI/EMI is coming
from the 240 volt power wiring but in my investigation I've come across a
couple of clues that this may be the main source of the issue. I'll
describe some more comments after the below links.
The first link is JPG of area around the 240 volt line input to the outside
condenser unit.
https://drive.google.com/file/d/1LulAakSfuktJbvGiRrQwPHTWSCRSziJK/view?usp=s
haring
The second link is a annotated Power Point of the same JPG, showing 240 line
input and 3 phase wiring to the Copeland 3 phase compressor.
https://docs.google.com/presentation/d/1Dp5RemNEcXDJrCTd94i9J5FkX-a--3-l/edi
t?usp=sharing&ouid=101983102297392238928&rtpof=true&sd=true
I would like to get some comments from the group about how the 240 line
input is routed very close to the 3 phase output from the inverter.
Notice that there are two toroids, one colored tan(3 phase inverter output),
the other colored green(240 volt line input) that are very close to each
other. I am thinking that because of the closeness of the two toroids there
is probably some coupling of 3 phase power signals to the 240 line input.
Also I've been looking at some of the documentation from Rheem about the
design and operation of the outside condenser unit with the 3 phase
inverter.
Here is some of the wording of the document when describing the filtering.
For the (-)P17 model line there are 3 ferrite
rings and one filter applied on all models. The
ferrite rings are similar in purpose to the choke,
whereas they create an inductive field around
the assembled wires, but they do not filter the
signals. The ferrite rings are applied only for the
purpose of keeping the high voltage lines from
cross contaminating one another and thereby
creating unexpected operation and Electro
Magnetic Interference. The single filter has been
applied to eliminate high frequency "noise" from
the incoming power line thereby making it more
efficient for the inverter to convert the incoming
high voltage single phase AC power into high
voltage 3 phase DC power.
What is interesting about that paragraph is that the filters and toroids are
meant to keep EMI ingress from entering the unit, NOT keep the EMI inside
the unit.
I have it in mind to add a 36 amp Corcom line filter to the 240 line input
in an external enclosure bonded to the metal enclosure of the outside unit.
I am also considering moving the internal filter board of the unit to the
external enclosure and re-routing the 240 wiring to keep it away from the 3
phase inverter power. Most likely placing it on the left side of the
enclosure as shown in the pictures. I might also change out the tan and
green toroids for type 31 devices. I can shut down the entire unit and
remove the existing toroids to measure them, before doing this.
Thanks for looking.
Karin Anne Johnson P.E. K3UU
Palm Harbor, FL
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