I have a 9k BTU Sanyo heat pump in my home office. Completely trouble free for over 10 years now. I love it. I installed a couple of Samsungs in some elevator machine rooms a few years back and they did not perform well, seemed a little under rated if you ask me. I also bought a Samsung refer at Best Buy a while back and the compressor lock rotor'd after 40 days. BB would not take it back because it was past the 30-day exchange warranty and I did not buy the "extended" warranty from them. Samsung service was a nightmare, and had mutliple compressor failures in the first 18 mos. Almost impossible to get parts or service for it. I ended up giving it away and buying a Kitchen Aid refer. I strongly reccommend AGAINST anything Samsung.

First off, 4 stories sounds like a big vertical head for residential mini-split equipment just from my casual notice of those requirements. I would check that out first. I am testing a whole-house mini-split installation right now (Mitsubishi, 7 in, 3 out). I will let you know in a year or so if I like it ;-) On paper they are more efficient due to inherent efficiency and the inherent zoned nature. We have been having pretty hot weather and with my wife out of town this week, I have been pretty much been cooling the bedroom and the kitchen with some intermittent cooling in the utility room where the exercise machine lives. Note that I am not much of a sit and watch TV type. You are really a leg-up over lots of others on this decision as you have experienced mini-splits. One thing to think about is that, IIRC, most of them don't have back-up heat so you will not have any heat while they are defrosting. (Maybe none of them have electric resistance back-up, but I think I ran across at least one brand that does.) You also have to pay close attention to cold weather performance for the mid-Atlantic region. I know that with Mitsubishi's current residential equipment, the 1:1 systems have better low temp performance than the multi-splits. They are more efficient too. Even if they do have back-up heat, you can kill the efficiency pretty fast if you need back-up very often. Keep in mind that there are lots of options to the wall-hung indoor units. They cost more, but there are units that can be dropped into ceilings and others that sit on the floor. There are also short, ducted units that would solve that big room problem by splitting the supply and return. (You could also install more than one indoor unit/room.) Condensate needs to be dealt with using pumps. I am not an HVAC or building pro, so take my observations with a grain of salt. After replacing a ducted system with mini-splits, and talking to my install guys a lot, here are some observations and conclusions. Installing a mini-split through outside walls, as is it usually promoted, is pretty quick and straightforward (read fast and cheap) compared to installing a new duct system in an existing house with no central AC. My install was done through interior walls running the lines/cables under the raised house and out to the side which was much more complicated. If I were doing this over and I had a good duct system within a house envelope, I would stick with it. The trouble is, what is a good duct system? More often than not, they are outside of the living space. In addition, they are considered good when they leak 5% of the air and they only get worse as they age. My system was in the attic with parts of the duct system in the attic and partly in a furred-down space over the hallway. The worst part was one duct that started at the AH in the attic, dropped down under the house in a chase and ran for about 30 feet before it reached the first floor register in an addition with a flat roof (thus no attic). It then reduced in size and ran another 25 feet under the house. That part might have been mini-splitted even if the rest of the house retained a ducted system. By your description, your duct system was not installed very well, but if the design is sound, it could be revamped less expensively than installing minis. In general, I think that ducted systems are trickier to design and install than mini-splits so there is more tolerance for less than careful and knowledgeable installers with mini-splits. Due to their ability to handle variable loads, choosing the right size is not as critical either. (I had 4 tons cooling plus a gas furnace before, now I have about 106% of the cooling and 60% of the heating. The heating was way oversized.) My system will handle cooling fine with the house the way it is, but I should not have trouble after I make improvements to limit infiltration and add insulation. My installer is knowledgeable, smart, very workmanlike, and experienced (he has taught the trade for 30 years). He would have installed new ducts and a two-speed system for a slightly lower price than the chosen mini-split equipment. I doubt that he would do it for the same price if doing it on a similar home going through interior walls. He did not have much mini-split experience and brought in a collaborator that does, on this project because he was looking forward to a learning experience. I don't think that he lost his shirt, but I don't think he made as much as he usually does.

> Is it cold and/or damp where you are? I'm in the Boston area — so in a word, "yes". > Is your system perhaps oversized for your home? Not according to my HVAC contractor, nor according to the beOpt simulations I ran. But that said, it's only in the 50s outside, so I would not expect the system to be working hard at this point. It's sized to handle 4 seasons, and the compressor is rated at 30 kBTU >I think error codes for Mitsubishi mini splits are displayed on the remote control and the control board on the outside unit. What is the model number of your outside unit? It's a MXZ-3C30NAHZ2-U1. I don't see any errors on the remotes, but I'll keep my eye out! > Did you install this mini split yourself or was it done by a HVAC contractor? I am not a mini split expert, but what you are seeing is not normal operation in my opinion. If there is an error code then you may be able to use the service manual to troubleshoot the problem. This was installed by a Mitsubishi certified installer who came highly recommended. That said, the install went quite poorly and I would not be at all surprised if they screwed it up.

Hi Elmer I read through your comments strongly supporting NG over HP option due to its cost advantage. Do you know a 10 KW solar system can be installed in CA today for $15000 after tax incentive , which will generate approx. 15000 KwH of electricity per year ? I am exactly doing this for my 1995 built 3375 sq ft home in bay area as this appears to be the cheapest route to bring down my energy cost as compared to other options like improve insulation, change windows or upgrade 1995 installed 80% efficient NG furnace etc. Till my NG furnace is alive and kicking, I plan to use it minimally in the morning to take the chill out of the home and rely on supplemental electrical heating ( resistive ) to keep the house warm . Resistive heating is inefficient, but ok as stop gap option particularly if my electricity is coming from solar. When it's time to bid farewell to these antique NG fired machines, I plan to take HP route for my home heating and air conditioning. Even without any of these actions and just install of solar, my current electricity only bill will be reduced from $2800 / year ( 10000 KwH ) to zero. That will pay for solar install cost in just 5 years. Add to it cost saving from an electric car ( which I don't have at this time ), payback is even shorter. My yearly NG heating consumption is 700-750 therms. The baseline consumption of 20 therms / month or 250 therms / year will always remain due to NG cooking appliance and NG water heater. But the rest 500 therms / year NG consumption can be eliminated when I replace central ducted existing NG Furnace / AC system with ducted heat pump (no splits). There will be more upfront cost to install heat pump as compared to NG furnace / AC option , but I am hoping this differential to be in the range of $2-3K , particularly if I go with heat pump option like MrCool Universal ( will work well in temperate Bay Area weather ) instead of fancy Fujitsu or Mitsubishi heat pumps. And saving of $1000 from eliminating consumption of 500 therms / year should help offset this cost sooner rather than later. Due to these considerations, I decided to go for 10KW Solar System that gives me enough capacity of solar generated electricity to meet these loads. Time to give a fresh look to all ( almost ) electric home with recent price reduction ( actually since June, 2020 ) in solar install cost.