Freon compressors in HVAC systems take something on the order of 30 min or
longer to achieve their design efficiency. Over sized units or units
running in marginally needed circumstances cool the space, satisfying the
thermostat but not circulating much air over the evaporator coils so they
don't dehumidify very well. A smaller unit will run longer (especially run
longer after achieving its design efficiency) and do a much better job of
dehumidifying. Proper dehumidification reduces the need for lower
thermostat settings to achieve equivalent comfort. Also the smaller unit
has many fewer starts and stops which contribute to their longevity as well
as spending a higher percentage of their time running after getting up on
their efficiency curve.
Most HVAC contractors are salesmen/installers, not HVAC engineers. They
make more money selling you a larger unit and get fewer callbacks because
they do cool the space. Unfortunately they don't do the job as well or as
economically regarding running costs or equipment repair costs as a "right
sized" unit. How to right size the unit with unpredictable demand?
Multiple compressors, variable speed compressors, or multi-speed compressors
are all approaches used to match cooling capacity to a moving target and
save on running and maint costs.
Multi-compressor setups should be no more RFI prone than the occasional
start or stop transient of a contactor making or breaking, Ditto for
multi-speed units. However, variable speed units can have widely varying
RFI signatures depending on how the speed controller is designed. Seems
from what I read here that no one is experiencing RFI from their variable
speed units.
The RFI generated when an electromechanical contactor makes or breaks can be
eliminated by replacing the electromechanical contactors (HD relays) with
solid state relays than "make" at the zero crossing of the voltage waveform
and therefore don't "make sparks" and "break" at the zero crossing of the
current waveform and again do not make sparks (switching transients.) Solid
state relays designed to do the above are available as COTS (Commercial Off
The Shelf) equipment from multiple suppliers.
I have three reversible heat pumps, one of which is geothermal, and hydronic
heat with zone controllers, remote control air duct dampers and water valves
and so I have a multitude of things switching on and off and am glad to
report I have not noticed any RFI from these sources. I can hear my
electric fence but not so strongly that it interferes with an otherwise
readable signal (most of the time) but on occasion if it rains and some
plant wet with rain leans over near a hot wire it will arc and generate a
stronger RFI. The fence operates at or above 10,000 volts and is a low
impedance source, pulsing at about a rate of about 1 pulse per second.
I think wall warts are the source of the little "mice" I see running to and
fro across my pan scope on the F5KA but they very rarely interfere enough to
warrant taking action against them.
Patrick AF5CK
-----Original Message-----
From: Jon Hall
Sent: Wednesday, June 19, 2013 7:05 PM
To: Terry Fox
Cc: flexradio@flex-radio.biz
Subject: Re: [Flexradio] Flex 5000A and RFI
I think the idea with the inverter technology compressors is that they vary
the compressor speed to maintain the temperature instead of cycling the
compressor on and off. The Mitsubishi unit I have runs the fan continuously
and the compressor drops to very low speed to maintain temperature. It's
how they are able to achieve 20+ SEER ratings.
Jon...kf2e
On Wed, Jun 19, 2013 at 1:53 PM, Terry Fox <t...@knology.net> wrote:
Not directly related, but I have a Chigo ductless mini-split here in the
shack. The problem that I had with it is that in cool mode, the fan is
always running while the compressor turns on and off as necessary. It has
a handheld remote control, so I figured out (with a LOT of Internet help)
the IR coding to turn the whole unit on and off. I now have an Arduino
with a small temperature probe that turns the Chigo on at a programmable
temperature, and turns it off at a lower settable temp.
I'm still playing with the user interface software. I'm using a 2x16 LCD
and five switches, similar to the popular Arduino LCD shields. I can
provide some info if anyone is interested.
73, Terry, WB4JFI
-----Original Message----- From: Jon Hall
Sent: Wednesday, June 19, 2013 1:23 PM
To: flexradio@flex-radio.biz
Subject: Re: [Flexradio] Flex 5000A and RFI
I have two of the Mitsubishi split heat pump/AC units installed in the
building with my shack. I tried turning them on and off and can't see any
difference in noise levels.
Jon...kf2e
______________________________**_________________
FlexRadio Systems Mailing List
FlexRadio@flex-radio.biz
http://mail.flex-radio.biz/**mailman/listinfo/flexradio_**flex-radio.biz<http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz>
Archives:
http://www.mail-archive.com/**flexradio%40flex-radio.biz/<http://www.mail-archive.com/flexradio%40flex-radio.biz/>
Knowledge Base: http://kc.flexradio.com/ Homepage:
http://www.flexradio.com/
_______________________________________________
FlexRadio Systems Mailing List
FlexRadio@flex-radio.biz
http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/
Knowledge Base: http://kc.flexradio.com/ Homepage:
http://www.flexradio.com/
_______________________________________________
FlexRadio Systems Mailing List
FlexRadio@flex-radio.biz
http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/
Knowledge Base: http://kc.flexradio.com/ Homepage: http://www.flexradio.com/
