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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