[RFI] Request for comments, Rheem HVAC

[Karin Johnson]

Thank you Dave,

Exactly what I hoping.

The inverter board and its associated electronics is quite sophisticated,

I have an energy monitoring system on my home, made by SENSE.

I have a current transformer specifically on the 240 line going to the 

Outside unit.  I can monitor and see the actual starting profile of the unit
when

It comes on line.  There is a slow ramp up of the compressor controlled by
the

Electronics behind the drive circuitry.  I am planning on a CORCOM type FC
rated 

For 36 amps.  According to the installation documentation for the Rheem unit
that

Should be enough. The maximum current I have actually seen is around a bit
more 

Than 20 amps.  This occurs when in heating mode.  It is a heat pump.

Normally during cooling the current is around 7 amps, unless I set the
thermostat 

To cool by more than about 2 degrees below the current temperature.

Printed documentation says max current for any condition is around 28 amps.

 

Karin 

 

  _____  

From: David Eckhardt [mailto:davearea51a at gmail.com] 
Sent: Sunday, October 03, 2021 2:03 PM
To: Karin Johnson
Cc: Rfi List
Subject: Re: [RFI] Request for comments, Rheem HVAC

 

 

I spotted the close proximity of the input 3-phase power and power to the
compressor right off the bat as did you.  Your other approaches are
certainly good, excellent, with the possible exception of composition of the
ferrite (or powdered iron) cores.  

 

All these cores are common mode chokes.  I can not judge on the
effectiveness as such based on the (few) number of turns through each
toroid.  Here is the color coding for cores from Amidon:

 

           http://www.qrz.lt/ly1gp/amidon.html

 

The tan core is phenolic and offers nothing in terms of inductance
enhancement (µr) due to the presence of the toroid.  These are all powdered
iron of one form or another and are not intended to do much as a common mode
choke or EMI suppression.  If that was the reason for their choice by Rheem,
they chose the wrong core materials for the cores.  Good
intentions.......bad execution.  They are more suited for hi-Q inductors
over their target frequency ranges.  I'd advise you leave those alone as
they may be doing something "unknown" to the casual observer regarding
performance of the unit.  However, I'd also advise augmenting each winding
with common mode chokes (all three wires through a common core for each with
nominally three passes through the each core) wound on 31 material which is
excellent for the CMC application.  Those included chokes do little for EMI
suppression.  CMCs would on 31 material should be much better at suppressing
EMI than the included toroidal chokes.  

 

Current rating of the proposed Corcom 3-phase filter:  Be sure the filter
will take the starting current draw on the compressor.  

 

Dave - WØLEV    

 

On Sun, Oct 3, 2021 at 5:00 PM Karin Johnson <karinann at tampabay.rr.com>
wrote:

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
<https://docs.google.com/presentation/d/1Dp5RemNEcXDJrCTd94i9J5FkX-a--3-l/ed
it?usp=sharing&ouid=101983102297392238928&rtpof=true&sd=true> 
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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-- 

Dave - WØLEV

Just Let Darwin Work