The AM Forum

Due to concerns with the current and future high prices and possible upcoming availability issue of of home heating oil we are looking at installation of a mini-split heat pump system for heating and air conditioning to supplement our oil fired baseboard heating system.  Been getting estimates from several local contractors.  

System is shaping up to be two Mitsubishi 30000 BTU outside units/compressors each supporting two inside 15000 BTU air handling heat exchangers (4 heat exchangers total).  The compressors will be the high performance units which remain efficient for heating at very low outside ambient air temperatures.

The compressors utilize, like a lot of things these days, variable speed DC motors powered by switched mode AC/DC converters. Obviously, I am concerned about interference from the inverters on HF radio reception.  I'm doing some on line research on this issue, and apparently there have been cases of amateur radio HF reception interference.  Has anyone on the forum had any experience good bad or indifferent re EMI from Mitsubishi heat pump systems?  Apparently there may also be variable speed SMPS inverter driven fans in the air handling units as well.  One of the outside units will need to be within about 5 feet of my main operating position in the basement, and the two associated indoor units will also be close by and above the station on the first floor.

Other related concerns are RFI interference to the microprocessors in the system from my station's HF transmissions, and the power quality tolerance of the systems when run on an emergency generator.  We currently use a DeWalt 7.5 KW copper wound two pole 3600 RPM genset, we also have a 17.5 KW 3600 RPM job site style Generac. Neither generator has problems running our relatively new direct drive motor LG washing machine. The washer does, however, generate serious HF EMI when running. We used to have a relatively early version direct drive GE washer which would not run on a generator. No problems running our relatively new oil fired furnace burner or baseboard control system and circulating pump on a generator either.

Chris,

   I would suggest that you find one installed somewhere around your neighborhood. The switching frequency can have an effect on the receiving situation. A portable SDR receiver with a whip antenna could be useful to sniff for RFI.

I have a large 5 Ton Lennox system with a 20 Khz VFD chopping rate. The outdoor unit is on the opposite side of my home, yet I have spurs every 20Khz up and down every band from 160-10m. On 20m, the spurs are S9 plus. A more modern unit might chop at 50Khz or 100Khz....likely a better starting point.

   One caution, if you add just 1 ferrite bead, and the service man comes by, even for a spring or fall cleaning and checkup, they may invalidate your warranty. If you have a hard failure, and they find anything you did, the warranty goes out the window.

Choose wisely..

Jim
Wd5JKO

I don't know the exacts of your systrm you are looking at, but....

Mitsubishi is pretty damn good.  To the point the federal government insists on their use at any new construction or remodels of existing facilities.

It is codified, under the "Buy American Act" that everything must be US made.....  Except for the Mitsubishi Split systems.

I have installed them at China Lake NAWS, Vandenberg Space Force Base (was AFB when I was there) and Edward's AFB.  In laboratories (as well as everything else).

We where required to use FMC (Flexible Metal Conduit) with an external bonding jumper from one end of the FMC to the other.  This made a continuous ground that did not depend on the conduit itself.....  Which is spiral wrapped (think like Heliax) and can have leakage issues when moisture gets in it (and this can't be stopped, eventually  it will get in) and can cause leakage.

I've also installed them a couple times at private residences.  Honestly I didn't notice an issue with the FT857 mobile.....  But also, I wasn't really paying attention.  However, it wasn't like the grow light issues in California where I could drive through a neigh or hood and tell you which houses where growing 'tomatoes'.

Hope this helps.  I do believe Mitsubishi units are the best you can buy, by far. 

--Shane
WP2ASS / ex KD6VXI
Sitting here in the dark, listening to Fiona bear down on us.....  With the sounds of the Hurricane Hunters coming and going.  God those guys and girls are brave!

Fiona......Stay safe Shane...  I installed a 36000 BTU "MrCool" mini split in my home.  Has a microprocessor and DC variable speed compresser.  My shack is 250 ft away from "mr Cool".  If I point my antennas at the house, I can see some 100hz lines on the screen for 15 meters and they are about S2.   I did drive a ground rod next to the unit and with a couple #6 solid Cu to the unit frame..  I haven't put any beads on the service wire yet, and I'm not worried about Warranty because I don't have a warranty as it was a DIY..  I'm pleased with the mini split...  Good luck .

Hi Chris,
I have a Mitsubishi high-performance system in the house. It is about 3 years old.
The 2 compressors are located just below the 2nd-floor shack and my OWL feedline runs right over them. The tower with the 6 and 2-meter beams is probably 30 feet away.
We have 5 heat exchangers including 1 in the shack. I've not noticed any RFI, or problems caused by my station to the system.
In addition, it does a great job of providing cooling and heat as needed in our 1840 farmhouse.

Best system around.  Zero interference issues.  I have two wall units installed in the museum and in retrospect, should have done the entire house with them.  My outside unit will handle 4 wall units and when the military, broadcast and library rooms in the museum is complete, the second unit will go in that space.   Mitsubishi brand is the best of the best although a bit more costly.  Very easy on the electric bill as well.  So much better than our upstairs Carrier Heat Pump.
Joe-GMS   

We had a 36,000 BTU Mitsubishi Mini-Split with 4 air handlers system installed mid-July this year.  The radio room is located about 35-40 feet from the main unit with the main antenna (135 ft OCF) approx. 50 feet distant.  I have noticed no increase in RFI since the installation.  We did notice an actual decrease (!) in our last electric bill, even with the units running 24/7 until a week ago during the hot WX this summer.  My wife did the research and was impressed with Mitsubishi as was the local company which installed the unit.  The near quiet running of the air handlers has been a welcome relief versus the replaced window AC's.   FYI there was an availability issue when we ordered the install, but fortunately it caused only a 2 week delay.  Good luck with your choice and install.