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Re: [RFI] Lennox brand HVAC RFI experience

To: rfi@contesting.com
Subject: Re: [RFI] Lennox brand HVAC RFI experience
From: Jeff Blaine <KeepWalking188@ac0c.com>
Date: Mon, 18 Jul 2022 22:34:24 -0500
List-post: <mailto:rfi@contesting.com>
I looked into the similar family 2-stage compressor unit.  Seems the 2-stage is done with respect to the fluid / gas compressive loading applied to a SINGLE speed motor.  So from my review of the manual, it seems this **may** be similar with respect to noise generation.  I suppose a control board could be located inside with some electronic goodies but I will have to check into that.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com


On 7/18/22 10:12 PM, Jeff Blaine wrote:
Thanks for that link Steve.  It looks like this Lennox heater uses exactly that 5-speed constant torque motor.  In looking at how those motors are constructed, and the layout of the control board, I don't see any sort of thing that screams "PWM IMPLEMENTED HERE SO LET THE WAVEFORM CHOPPING CONSOMME AND LETS RIP SOME RFI!!!"

I had a long talk with my HVAC guy, and showed him the shack, and the test gear and so he was comfortable that I would be able to implement any abatement - if needed - especially since any 120/240 stuff would have my electrician's seal of approval and keep them off the hook for "user tampering" or whatever other things they may be worried about.  And from that, we did not talk about any of the variable speed this and that solutions out there.  It was all single/dual speed only.  No variable anything.

I've got a few messages from guys saying the RFI issue was contained (in those cases) by following the generic suppression stuff (common mode primary, some differential if needed - and a bit of shielded runs to the thermostat in one case).  I suspect that I could make a variable speed system work but it looks simpler and may be a higher chance of no-problem if I just stick with the dual speed options which is where I am now.  In fact, I may consider a 2 speed aircon compressor if those are winding-selected 2-speed implementations instead of 2-setting variable speed things.  Need to check more.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com


On 7/18/22 6:57 PM, Steve London wrote:
This is certain to raise W0LEV's blood pressure:
http://library.coburns.com/HVACTechTips/Motors%20what%20is%20going%20on.pdf

GL finding a new PSC-motor furnace and compressor. If you find one, please post it - I'm in the same position as AC0C.

73,
Steve, N2IC

On Mon, Jul 18, 2022 at 3:55 PM Jeff Blaine <KeepWalking188@ac0c.com> wrote:

    We are looking at a replacement HVAC and these items are proposed for
    the install.  I'm paranoid about the RFI noise profile out of modern
    HVAC systems and would be interested in any comments.

    The Lennox P/N recommended are:

    Merit series - ML14XC1$-042 compressor 14 SEER

    Elite series - EL280UH090E488 dual-speed (2-stage?) furnace 80%

    The installer is aware of the Lennox 604552-01 kit which includes a
    differential filter and a snap-on toroid.  I've made it clear that
    the
    single snap-on toroid is likly and that a multi-turn type 31 would be     used in lieu if needed.  Which would not have a warranty issue as the
    HVAC guy and I share a common electrician who has vouched for the
    safety
    of this "mod."  And we have discussed that similar (multi-turn
    toroid)
    treatment may be added to the thermostat line as well.

    Appreciate any advice on other guys who may have experience with
    Lennox
    gear in general, or these families in particular.

    73/jeff/ac0c
    alpha-charlie-zero-charlie
    www.ac0c.com <http://www.ac0c.com>


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