The room to be conditioned is a great room with a cathedral ceiling ... no attic. The only exterior wall has a fireplace and a pair of windows ... no space for an indoor unit. The other 3 walls are either covered with furnishings or are archways to other rooms. This is the reason that I chose to put a unit in a closet that separates the great room from another part of house. This closet is 24" deep on the interior and about 40" wide; the 24" side is adjcent to great room. I had cosidered putting a ducted evaporator in the closet, but they all seem to be 35 to 42 " wide ... thus it will not fit. I also considered using one of the ceiling mounted units that are about 24" square. To do this I would have to mount it upside down on top of the free standing closet. I understand that this will not work because drainpan will not catch condensate. Further, these units will not handle the 2 ton that I think we need.
At this point, I think the closet will get a conventional air handler that takes air in at the bottom of the closet and blows it out the top toward the top of the cathedral ceiling. I am concerned with noise levels as the closet is only about 7' high which means the blower will be close to the supply and return to the living space. I'm considering a 2 stage compressor so it can run at a low speed most of the time an only run high when necessary. I have not found documentation concerning what controls the speed.
Is it possible to run a mini-split compressor with an conventional air handler? I don't know what kind of control signals are available to get these 2 units to work together and to modulate speed when necessary. Further, I don' know if any manufacturer woud warranty such a configuration.
I appreciate \your thoughts and thanks for comments to date.
Most mini-splits, have what are known as inverter style compressors. This is how they work.
They convert the 240v, 60hz AC, into DC. Then they INVERT that DC into 240V AC, 5 to 120 HZ.
This allows the compressor to be almost INFINITELY variable. When the room cools down, it cranks down to 5 HZ and just trickles in the refrigerant.
Because of this, you will not be able to interface it with a normal air handler.
Most of the big Mini Split manufactures, however, make small air handler type units.
They also have outdoor condensing units, that can connect up to 8 (the most that I have seen) indoor units.
You might also want to check out a product from LG, called their ART COOL.
It is an indoor unit that mounts on an interior wall, that looks like a picture frame. Well, it is an actual picture frame, and you can put whatever picture you want in there.
it is about 4 to 8 inches thick and it looks nice if placed well.
It also gets up into the 20 SEER range.
If you have anymore questions, please feel free to ask.
Tony ... The variable speed capability of inverter technology is why I think a mini-split is applicable in this case. I would like to know what acturally controls the speed; is it temperature, line pressure or ??
Sir-Fixalot: I can't speak to how other manufacturers do it, but from the Mitsubishi classes I have been to, it seems like the mini split inverter compressors are controlled based on temperature sensors. There are thermistors for ambient air, outside coil temp, compressor discharge temp, indoor coil refrigerant entering temp, indoor coil refrigerant leaving temp and room temp.
The outdoor unit communicates with the indoor unit and reads the indoor temps and adjusts speed and LEV position to attempt to maintain a specific change in refrigerant temp based on how far the room temp sensor is from the setpoint.
Since this is a communicating system, it would be difficult to "trick" the condenser into working with another type of fan coil. Maybe if you had all the boards and sensors from a proper indoor unit? Still seems risky to me.
One of my customers would like to install air conditioning. They have hydronic heat and the house is relatively small. I thought that a mini-split would be ideal. The problem is that most indoor units are 35 to 45 inches wide and I just don't have a home for this. Does anyone know of an indoor unit that is about 24 inches wide. I would be installing this in a free standing closet and blowing the conditioned air out the top into a great room. I probably could install a conventional system, however, because the closet is in the living space, I am concerned about the sound level. Suggestions would be appreciated. Thanks
If this house has a basement with room maybe consider a unico system. They are high velocity with 2" supplies, very discreet use the closet as a return. If they are installed properly they work very well and would be much quieter than an air handler in the living space. Just round pipe for the trunk line ( they call it the Plenum)