Joanne,

Mini splits (whether a floor / wall or ceiling mounted makes little difference) biggest down fall fits most squarely into this category. Most of them use proprietary controls that can be rather limited. The bigger problem however, is that they are designed to be "spot cooling / heating appliances" the spot is essentially the room in which it sits and maybe 10-20 feet around it and even that circumference may be stretching things a bit.

The supply to the unit is at the unit. The return to the unit is at the unit. The more extreme the climate the bigger the room or area you are trying to condition?

Sorry not likely for a remote thermostat to make much difference.

The unit is sized for the room. If the structure is a single room structure that is where a mini split performs best.

Traditional HVAC is sized for the whole structure, the throw (or reach of the system) is made possible by traditional "leaky inefficient ducts" --- but those get the job done.

People like to add remotes to traditional HVAC products when realistically they could just set the thermostat they have lower, same effect. Without zoning (costs more) so these remotes stats are the hook for people who don't truly understand what they are trying to do.

So have you tried raising or lowering the temp to the thermostat you have now? What was the effect of that? What makes you think the effect will be different with a remote thermostat?

The guy (your guy) appears to me to be smarter in the sense he doesn't waste his time telling you the effect just quotes a price high enough to let you "pay the price" -- reap the rewards of you thinking what will fix it / that will not even come close 9 times out of 10.

The thermostat (no matter which kind you use / type / remote or other) is a sophisticated switch that does nothing more than turn the unit on or off. The setting of that stat has no bearing how much or how little (heat or cool) will be supplied. Thru the significance of the passage of time and the unit running significantly long periods, maybe (if the conditions are right) your thermostat number is reached the unit then finally cycles off.

Furthermore, design problems are rarely ever fixed this way. To truly fix it, you need a new design or you live with xyz problem, what ever it is.

So with a mini split bonanza what is the fix? probably add another mini split in the area in which comfort is lacking. The con? equipment poor, maintenance poor, but more comfortable.

I service the Katy, Texas area.

Thanks. I understand what you are saying. I do understand that the heat coming out of the unit is basically pulled back into the return before circulating around the room.

Not exactly sure why a thermostat across the room from the unit would not cause the unit to run for a longer (or shorter) time until the remote thermostat is satisfied. When I set the thermostat higher (or lower, when cooling) than I want the actual temperature to be, it runs long enough to heat the whole room, more or less.

I still have a boiler and baseboard heating system, we mostly put in the HPs for the AC.

I opened up the unit to take a look at the circuit board. there is no red port as far as i can see. wondering how the tech would be installing one without it. they know which model they installed.

What is the full model number to the unit?

I have two separate systems, this is the one in question, specifically the living room, which gets the most use. Dining room is adjacent and kept at about the same temp. BRs are upstairs and rarely used, but seem to work ok. The MHK2 is supposed to be compatible with this floor mount, according to the Mitsubishi website.

Well Joanne, I found it and do not believe it's red. I pulled up the service manual for the MFZ-kJ12NA in-door unit and the wiring diagram on page page 8 clearly shows a CN105 port but not it's true location.

Link to manual: https://www.totalcomfortmech.com/hubfs/Mitsubishi/mfz-service-manual.pdf

But on page 35 there is a test point diagram of the main board and shows exactly where the CN105 port is on the board. It's behind the 15 yellow and orange wires and to the right and in line with the 5 white wire plug.

It's a 5 pin port with a label on the board as CN105 but I can't tell what color it should be. There could of been a color change to indicate a difference between older models that were compatible with Honeywell controllers and the MHK1 controller using a red port, and your newer unit isn't compatible with the above controllers. Maybe this is why I saw the MHK1 on clearance for $79.00 on a HVAC web site, companies do like to keep their toys proprietary.

Thanks, this helps enormously. I’ll take a closer look at the board and the service manual. The instructions for set up do look a bit daunting.

"the wiring diagram on page page 8 clearly shows a CN105 port but not it's true location."

Correct. The diagram on page 11 gives a better idea of where the CN105 is located.

"It's behind the 15 yellow and orange wires and to the right and in line with the 5 white wire

plug."

I'd say more accurately that it's to the right of the 15-orange-and-yellow-wire plug and below the 5-white-wire plug.

• Mitsubish MHK2 at HVAC Direct, on ebay
• Spec sheet
• Installation Instructions

The MHK2 consists of three parts: the MRCH2 Controller (wall-mounted thermostat), MIFH2 Receiver (that communicates with the thermostat), and MRC2 Cable (which plugs into the CN105 jack on the circuit board and the MIFH2).

I think you can perform the installation yourself by following the steps on pages 1-6. Page 7, Initial Installer Setup references the settings (ISUs) you can adjust that are listed on page 10-11 but these all have defaults which you can probably leave unchanged (ISU 151 controls how you can configure schedules; the default is one schedule for weekdays and another for weekends). Note that the 28 modes shown on pages 8-9 are set automatically.

I have ordered one and will update on how it goes. I love this stuff, can’t wait until it’s here.

Until it arrives, use two thermometers. One on the unit and one where you intend to mount the remote. Turn the unit on and dial it up to a high temp setting. When the remote location reaches your comfortable temp level look at the reading for the air temp at the unit. Set the unit to that temp. Done.

Do you mean to put a thermometer directly on the unit?